JP7253864B2 - Solidification refinement and global phase transformation control by application of in-situ gas jet impingement in metal additive manufacturing - Google Patents

Description

RELATED APPLICATIONS U.S. Patent Application Serial No. 16, 14/1 entitled "SOLIDIFICATION REFINEMENT AND GENERAL PHASE TRANSFORMATION CONTROL THROUGH APPLICATION OF IN SITU GAS JET IMPINGEMENT IN METAL ADDITIVE MANUFACTURING 0," filed June 26, 2018; and U.S. Provisional Patent Application No. 62/527,656, entitled "REFINEMENT OF SOLIDIFICATION STRUCTURES IN ADDITIVE MANUFACTURING BY MELT POOL GAS JET IMPINGEMENT," filed June 30, 2017. do.

Where permitted, the subject matter of each application referenced above is incorporated herein by reference in its entirety.

The present invention relates to an apparatus and method for manufacturing objects, particularly titanium and titanium alloy objects, by solid freeform fabrication.

Structured metal components made of titanium or titanium alloys or other alloys have traditionally been made by casting, forging or machining from billets. These techniques have many disadvantages, including high material usage of expensive titanium metal and long lead times in the fabrication of metal objects. Casting, which can often be used to produce objects that can be near net shape, typically suffers from poor material quality due to lack of control over solidification and cooling rates. Tooling costs and the inability to fabricate complex shaped objects are other drawbacks of conventional methods.

Fully dense physical objects can be made by manufacturing techniques known as rapid prototyping, rapid manufacturing, additive manufacturing, or additive manufacturing. Additive manufacturing offers greater manufacturing flexibility and potential cost savings through the layered construction of near net shape products. It is desirable to match the material properties of conventional thermo-mechanical processing methods such as forging while utilizing the same existing metal alloys.

In thermo-mechanical processing, material properties are mostly the result of grain structure refinement achieved by recrystallization induced by the plastic deformation of the mechanical forming step. This mechanism is not available in typical additive manufacturing processes where molten material is added in layers and allowed to solidify and cool without mechanical shaping. The result is typically a coarse grain structure in the solidified state. In many alloys, the resulting structure is also elongated with a high aspect ratio. This is due to the directional heat removal provided by the relatively cold workpiece when superheated molten metal is added. Solidification starts in the previously deposited layers and propagates to the deposited material as the deposited layers cool. Solidified structures often extend across several layers and are several centimeters in size. These properties are typically sub-optimal for mechanical properties, resulting in reduced and/or anisotropic strength, elongation, and fatigue performance. Upon further cooling after solidification, allotropic phase transformations (transformation from one crystal structure to another), precipitation, and other solid state thermochemical reactions occur. These properties are determined by the alloy system in question. The cooling rate in the critical temperature range where these transformations occur is a major concern. Layered additive manufacturing processes create complex, repetitive heating, cooling and reheating conditions where control of all relevant phase transformations for each deposited layer is essential to obtaining a consistent product. Achieving thermal control despite varying workpiece geometries, heat dissipation characteristics, and accumulated heat is therefore a challenge faced in additive manufacturing. In addition to the effect of the cooling rate on areas that have just been deposited and solidified, the cooling applied after deposition also contributes to the overall cooling of the workpiece, allowing new strings or layers to occur without significant waiting time. Allow deposition to begin. This is particularly beneficial for compact geometries with short cycle times between strings or layers. In-situ gas jet impingement in the targeted phase transformation region can increase cooling rate and provide solidification refinement and overall phase transformation tuning and/or control.

The prior art includes, for example, the use of hybrid processes that plastically deform each deposited layer to obtain a recrystallized grain structure, applied to reduce strain and improve mechanical properties (US Pat. See Liou et al. (2015)). However, such an intermediate shaping step can reduce the effective deposition rate (negatively impact productivity) and limit shaping flexibility in terms of the ability to form complex shapes. Other techniques are interlaminar laser peening and ultrasonic impact treatment, as described in US Pat. Including interlaminar cold rolling, such as

Forced cooling has been applied to the solidified layer during the cooling of the solidified metal in preparation for laser or ultrasonic impact treatment to reduce thermal strain and refine the grain structure as a result of recrystallization (Patent Reference 4, Wescott et al. (2015)). This helps reduce the wait time between layers, but requires waiting for the workpiece to reach the optimum temperature before conditioning the as-deposited layers, which reduces productivity. It can be adversely affected and limit the shaping freedom. None of the prior art mentions applying any cooling during deposition and never applying cooling (in situ) to the weld pool or to areas adjacent to the weld pool during deposition. Instead, Wescott et al. describes cooling the solidified layer of the string of workpieces between string depositions to prepare for the deformation step. Contaminants from tooling are also a concern, as additional processes can introduce some contaminants between the layers of the final product in the way the deposited layers are physically functioning. Wescott et al. did not mention refinement of the solidification structure in additive manufacturing by molten pool gas jet impingement.

Other techniques that have been used to refine metals to achieve grain refinement are the application of mechanical vibrations (see, for example, US Pat. 6, Shack et al. (2014)), or by an oscillating electromagnetic field (US Pat. No. 7, Jarvis et al. (2015)). In addition to the potentially prohibitive cost and lack of practical implementation methods, the effectiveness of the general principle of molten pool stirring is very limited for many of the metal alloys involved. Specifically, molten pool agitation requires a zone of partially solidified material in the propagating solidification front so that fracture can break the solidification front. A property of many titanium alloys, especially many alloys applicable to additive manufacturing, such as the main titanium alloy Ti-6Al-4V, is a narrow solidification temperature range, which is controlled by acoustic vibration mechanisms, electromagnetic vibration mechanisms. , or through techniques that utilize a vibrating mechanism, such as a mechanical vibrating mechanism, making the alloy highly resistant to fracture of the solidification front.

U.S. Patent Application Publication No. 2015/0360289 International Publication No. 2013140147 pamphlet EP-A-2962788 U.S. Patent Application Publication No. 2015/0041025 U.S. Pat. No. 3,363,668 U.S. Patent Application Publication No. 2014/0255620 International Publication No. 2015028065 Pamphlet

Thus, the art describes a finer grain structure, particularly more equiaxed grains, after additional cooling below the relevant phase transformation temperature compared to what is achieved in conventional additive manufacturing processes. There is a need for an economical method of performing metal additive manufacturing with increased metal deposition rates in additive manufacturing systems that produce metal products with more consistent microstructures.

Accordingly, the present invention is directed to refinement of solidification structures in additive manufacturing by gas jet impingement in a melt pool that substantially obviates one or more of the problems resulting from the limitations and shortcomings of the prior art. An extension of the device, a separate gas jet device, can be used to achieve in-situ thermal control of the deposited and solidified material. Apparatus, system and apparatus for refining solidified structure and controlling microstructure during metal additive manufacturing to obtain products with improved material properties, particularly products with a more equiaxed grain structure in the solidified state. A method is provided. Manufactured products with these refined grain structures exhibit improved strength, fatigue resistance, and ductility. Further, there is a need in the art for methods to improve the throughput and yield of metal products produced by metal additive manufacturing processes.

An advantage of the present invention is that the resulting grain structure has aspect ratios and homogeneity comparable to grain structures typically present in machined metals, and significantly less than typical cast or additively manufactured materials. and to provide grain refinement in metal articles produced by additive manufacturing having a reduced average grain size.

Apparatus and methods provided herein provide a method for forming a layered metal deposit using additive manufacturing to the free surface of a weld pool, or to a liquid-solid interface, or to a liquid-solid interface. Gas jet impingement on nearby solidified metal, or on solidified metal, or any combination thereof, results in refinement of the solidified structure and microstructural control. The gases used can be inert or non-inert, elemental or mixed gases, depending on whether the metal alloy in question is susceptible to atmospheric pollution.

Optimization of microstructural grain size and material properties in different parts of the deposit is also possible using the apparatus and methods provided herein in additive manufacturing. The apparatus and method provide a viable method for achieving significant refinement of metal structures, resulting in most cases being slightly coarser than typical machined metals, but with comparable aspect ratios and Resulting in grains with homogeneity. Cooling gas jets directed at the liquid surface and liquid-solid boundary of the weld pool can induce and accelerate opposing solidification fronts at the weld pool free surface. Epitaxy inhibition can be achieved when a continuous layer nucleates and solidifies from the grains of the top layer. When applied to materials in the solidified state, forced cooling by the concentrated gas turbulence provided by the apparatus provided herein can improve, tune or control solid state transformations.

Another advantage of the present invention is that the apparatus and method allow manipulation of solidification conditions in many metal alloys without the need for time-consuming adjustments between layers, constraints on geometry processing, or significant reductions in deposition rate or deposition productivity. and to realize significant miniaturization potential. By the use of a cooling jet device for forced cooling of the deposited material during additive manufacturing by in situ application of a jet of cooling gas at the target area, either alone or in combination with a cooling jet device directed at the melt pool, Deposition productivity can be significantly increased. A large flow of cooling gas from the jet device directed at the as-deposited material can remove significant thermal energy, resulting in an enhanced bulk cooling rate of the deposited material. The cooling jet apparatus provided herein can be configured to work with most melting tools and can be adjusted, activated or deactivated at any time during deposition in the additive manufacturing process. state can be made. This flexibility gives the ability to change the underlying grain structure of the manufactured product during the manufacturing process. The method can be used with any metal additive manufacturing process and laser system, including plasma and wire-based processes, and is particularly suitable for high deposition rate processes. Although Ti and Ti-alloy work pieces are mentioned as examples throughout, the method may be equally suitable for many other alloy systems based on metallurgical theory. For example, Inconel superalloys are also amenable to the refinement effects achieved using the apparatus, methods and systems provided herein.

A spouting gas stream from the spouting devices provided herein directed at the weld pool, such as the weld pool free surface, can increase crystallographic diversity and reduce grain boundary alignment. can do. Directed blast gas can result in different microstructural elements that are present in a more homogeneous and finely dispersed state. Typically, additively manufactured metal products can include the presence of columnar solidification structures that extend for several centimeters across the deposited layer. These columnar solidification structures can be broken by irregularly spaced finer grains due to slight variations such as thermal gradients and weld pool convection. The jet tools provided herein, when directed at the weld pool, can induce or promote nucleation at the free surface of the weld pool with reduced temperature gradients, resulting in additively produced material. leading to fractures of the columnar structures that previously existed in , resulting in improved and reproducible material properties.

Another advantage of the present invention is that the apparatus and method allow adjustment of the cooling rate during the additive manufacturing process. In additive manufacturing, multiple elements, most commonly referred to as strings, beads, or tracks, can be stacked together to form what are typically very complex shapes. The string is formed by feeding metallic material, typically in wire or powder form, to a moving heat source where the supplied energy of the heat source melts and fuses the metallic material. The heat source can be a high energy laser beam, electron beam or plasma arc, or any combination thereof. This layered deposition can create complex, cyclical and transient thermal conditions. It is cyclical, as previously deposited material is typically reheated by the deposition of successive layers, and transient due to changes in boundary conditions, such as heat dissipation properties, as the build progresses. be.

Most metal alloys are susceptible to thermal history. Typically, the cooling rate from the high temperature of the string deposition to the bulk temperature of the workpiece has a large effect on the final material properties. In addition, the effects of heat input from successive layers can change material properties through in-process annealing and aging effects. Therefore, it is important to control local thermal conditions to provide consistent material properties throughout complex additive manufacturing products. The invention disclosed herein is a device that enhances the ability to adjust or control thermal conditions in additive manufacturing through the application of in-process temperature measurement and the application of forced convection cooling using the jet device provided herein. , systems and methods.

Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages, and to embody and broadly describe, in accordance with the objects of the present invention, a jet device comprising an inlet for receiving cooling gas and a jetting device for discharging cooling gas. and a second conduit including an inlet for receiving the cooling gas and an opening connected to the nozzle for discharging the cooling gas; One conduit is attached on one side of the thermal energy source to the melting tool that produces the thermal energy source, and a second conduit is attached to the melting tool on a second side of the thermal energy source, at least one the nozzle is configured to create a turbulent flow of the cooling gas as it exits the nozzle, and is configured and positioned to prevent the nozzle from blowing the cooling gas toward the thermal energy source; A jet device is provided.

At least one conduit including an inlet for receiving a cooling gas and one or more openings each connected to one or more nozzles for in situ discharging the cooling gas onto the material in its deposited state. A jet device is also provided, comprising: The jetting device may be configured to include multiple conduits each including an inlet for receiving the cooling gas. The conduit may be configured to deliver a jet of cooling gas in situ to one or more surfaces of the material in its as-deposited state. By way of example, a single conduit may be configured to include multiple nozzles, some of which may be configured to direct a jet of cooling gas onto one side of the as-deposited material. other nozzles can be configured to direct cooling gas jets to other sides of the as-deposited material, and other nozzles can direct cooling gas jets to the top surface of the as-deposited material. can be configured to direct the As another example, the jetting device can include multiple conduits, one conduit can be configured to include a nozzle that directs a jet of cooling gas at one side of the material in the as-deposited state; Two conduits may be configured to include nozzles that direct cooling gas jets to the other side of the as-deposited material, and a third conduit directs cooling to the top surface of the as-deposited material. It can be configured to include a nozzle for directing the gas jet. A jetting device can be connected to a portion of the system at a point that allows the nozzle to be directed at the surface of the solidified material as it is deposited. In some configurations, the jet device can be connected to a wire or powder feeder. The jet device can be connected to a bracket or support to be independent of the wire or powder feeder.

The system provided herein includes a jet device for directing a cooling gas jet in-situ at the material in the as-deposited state, and at least two devices for monitoring the temperature of the application area of the cooling gas jet during an additive manufacturing process. and a temperature sensor. A first temperature sensor can monitor the temperature at the surface of the as-deposited material prior to the application of the cooling gas, and a second temperature sensor located behind the jetting device can It can be included to measure the temperature of the surface of the workpiece after the cooling gas has been applied to the as-deposited string of workpieces. Temperature data from the first and second temperature sensors may be used by a user to adjust the cooling rate by adjusting the flow rate of the cooling gas applied by the jet device, or the direction of flow of the cooling gas toward the workpiece, or both. can be controlled.

In another aspect of the invention, a system for constructing a metal object by additive manufacturing, comprising: a first melting tool for preheating a base material prior to deposition of molten metal; A second melting tool for making droplets of metallic molten material deposited on or into the liquid pool on the preheated base material and across or impinging on the liquid pool. or to impinge the solidifying material adjacent to the liquid-solid boundary of the liquid weld pool, or any combination thereof; A source, a system for positioning and moving the preform with respect to the heating device and the jetting device, and a device for reading a design model of the metal object to be formed and using the design model to position and move the preform. Controls capable of adjusting the position and movement of the system and operating the heating and jetting devices so as to build a physical object by fusing a continuous deposit of metallic material onto the base material. A system is provided, comprising:

In another aspect of the invention, a method for producing an object of metallic material by additive manufacturing, wherein the three-dimensional object is created by fusing together successive deposits of metallic material onto a base material. preheating at least a portion of the surface of the base material using a first melting tool; and heating and melting a metallic material using the spouting device provided herein across or impinging on the liquid weld pool, or directing the cooling gas to impinge on the solidified material adjacent to the liquid-solid boundary of the solidified state, or any combination thereof, and a continuous deposit of molten metallic material; and moving the preform in a predetermined pattern with respect to the positions of the first heating device and the second heating device such that the solidifies to form a three-dimensional object. In the method, the jetting device may direct the cooling gas jet to the molten pool, or may direct the cooling gas jet to the solidified deposited metal region, or one jetting device may direct the cooling gas jet to the molten pool. The jets can be directed, and a second jet device can direct the cooling gas jets onto the region of solidified deposited metal.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. sea bream.

The accompanying drawings, which are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, illustrate embodiments of the invention. It serves to explain the principles of the invention.

FIG. 1 is a schematic perspective front view of an exemplary spouting apparatus for providing directed gas jets at the free surface of the weld pool and the liquid-solid interface as the molten material is deposited to form a string; be. Not shown in this figure are the melting tools located above the molten pool, or the wire or powder feedstock fed to the molten pool or to the melting arc or laser beam. FIG. 2 is a partial cut-away side view of an exemplary configuration of a jet device. FIG. 3 is a schematic cross-sectional view of a single-row wall stack as layer upon layer is fused. The figure shows typical non-refined grains in the first three layers followed by the refinement mechanism of columnar grain growth inhibition by application of gas jet impingement using the jet apparatus provided herein. Show growth. FIG. 4A shows a conventional additive manufacturing process compared to that achieved using the method provided herein (FIG. 4B) where gas jet impingement results in a material with finer grains. Figure 4A shows an electron backscatter diffraction (EBSD) photograph of crystallographic analysis of a typical material (Fig. 4A) made by FIG. 4B is a conventional additive manufacturing process compared to that achieved using the method provided herein (FIG. 4B) where gas jet impingement results in a material with finer grains. Figure 4A shows an electron backscatter diffraction (EBSD) photograph of the crystallography of a typical material (Fig. 4A) made by FIG. 5A shows a typical structure of a deposited Ti-6Al-4V sample (FIG. 5A) showing molten pool gas flow into a multi-row multi-layer Ti-6Al-4V deposit using the spout apparatus provided herein. Fig. 5B is a photomicrograph compared to the resulting refined structure by application of jet impingement (Fig. 5B). FIG. 5B shows a typical structure of a deposited Ti-6Al-4V sample (FIG. 5A) showing molten pool gas flow into a multi-row multi-layer Ti-6Al-4V deposit using the spout apparatus provided herein. Fig. 5B is a micrograph compared to the resulting refined structure by application of jet impingement (Fig. 5B). FIG. 6 is a photograph showing the results of applying gas jet impingement to half of the weld pool in a single row Ti-6Al-4V deposit using the jet apparatus provided herein. The dotted line roughly indicates the typical grain size and shape of one side of the wall. FIG. 7 is an illustration of providing gas jets directed at the solidifying metal region as the molten material in the molten pool cools and forms strings to affect additional phase transformations that occur after solidification and further cooling. 2 is a schematic side view of the jet device of FIG. A melting tool positioned above the molten pool provides energy to the molten metal falling into the molten pool to melt the metal wire or powder feedstock. A temperature sensor can be positioned in front of the jet apparatus to measure the temperature of the string during forming, and a temperature sensor can be positioned in front of the jet to measure the temperature of the solidifying metal during or after application of the gas jet. It can be located behind the device. FIG. 8 is a schematic side view of an exemplary system that can be used with the methods provided herein. In the depicted embodiment, a single melting tool is used to form the molten material that is deposited to form the deposit, and a first jetting device is used to deposit the molten material to form the string. Sometimes directing a jet of cooling gas at the free surface of the molten pool and at the liquid-solid boundary, and a second jetting device that can cause allotropic transformation or precipitation as the molten material cools. A jet of cooling gas is directed at a solidifying metal region, such as a region. FIG. 9 is a schematic side view of an exemplary system that can be used with the methods provided herein using two melting tools. In the depicted embodiment, one melting tool is used to preheat the substrate surface to form a preheated region, and a second melting tool heats the metal onto the preheated region of the base material. is used to melt and form a deposited string, and the first jetting device impinges on the free surface of the molten pool and the interface between the liquid and the solid as the molten material is deposited to form the string. A cooling gas jet is directed, and a second jetting device directs the cooling gas jet to areas of the solidifying metal, such as areas that may undergo allotropic transformation or precipitation as the molten material cools. FIG. 10A is a micrograph showing the correlation between bulk cooling rate differences and the microstructure of the Ti-6Al04V material. FIG. 10B is a micrograph showing the correlation between bulk cooling rate differences and the microstructure of the Ti-6Al04V material.

Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.

A. Definitions Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents, patent applications, published applications and publications, websites, and other published materials referenced throughout this disclosure are incorporated by reference in their entirety unless otherwise noted. . If there are multiple definitions for terms in this specification, the ones in this section take precedence.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

As used herein, ranges and amounts can be expressed as "about" a particular value or range. "About" also includes exact amounts. Thus, "about 5 percent" also means "about 5 percent" and "5 percent." "About" means within typical experimental error for the intended use or purpose.

As used herein, "optionally" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the described event or circumstance occurs It is meant to include cases and cases where an event or situation does not occur. For example, an optional component within a system means that the component may or may not be present within the system.

As used herein, "combination" refers to any relationship between two items or among three or more items. This relationship can be a spatial relationship or refers to the use of two or more items for a common purpose.

As used herein, “additive manufacturing,” also known as “additive manufacturing” and “additive layer manufacturing,” refers to 3D model data, metal sources, such as wires or powders, and metal sources. Refers to an additive process that carries out the layer-by-layer fabrication of an object from an energy source (such as a plasma arc, laser or electron beam) for melting.

As used herein, "additive manufacturing system" refers to machines used in additive manufacturing.

The terms "plasma transferred arc torch" or "PTA torch", used interchangeably herein, refer to the heating and excitation of an inert gas stream into a plasma by an electric arc discharge, followed by an orifice (such as a nozzle). ) and is capable of forming a suppressed plume that extends out from an orifice and transfers the intense heat of the arc to a target area.

As used herein, the term "metallic material" refers to any known or conceivable metal or metal alloy that can be used in a solid freeform fabrication process to form a three-dimensional object. Examples of suitable materials include, but are not limited to, titanium and titanium alloys, such as Ti-6Al-4V alloy.

As used herein, "plasma arc welding torch" or "PAW torch" refers to a welding torch that can be used in plasma arc welding. The torch heats the gas to a high temperature to form a plasma that becomes conductive, which then transfers an electric arc to the workpiece, and the intense heat of the arc melts the metal and/or separates the two metals. It is designed so that the pieces can be fused together. A PAW torch can include a nozzle for constricting the arc, thereby increasing the power density of the arc. The plasma gas is typically argon. A plasma gas can be delivered along the electrodes to ionize and accelerate in the vicinity of the cathode. The arc can be directed toward the workpiece and is more stable than a free burning arc (such as in a TIG torch). PAW torches also typically have an outer nozzle for providing shielding gas. The shield gas can be argon, helium, or a combination thereof, and the shield gas helps minimize oxidation of the molten metal. The current is typically up to 400A and the voltage is typically in the range of about 25-35V (but can be up to about 14kW). PAW torches include plasma transferred arc torches.

As used herein, the term "base material" refers to the target material for heat from the melting tool and on which a molten pool can be formed. The melting tool can be a PAW torch, a PTA torch, a laser device, or any combination thereof. The matrix provides a holding substrate for depositing the first layer of metallic material. When one or more layers of metallic material are deposited on the carrier substrate, the base material becomes the top layer of deposited metallic material upon which a new layer of metallic material is to be deposited.

As used herein, the term "workpiece" refers to a metal object produced using solid freeform fabrication.

The terms "design model" or "computer-aided design model" or "CAD model", as used interchangeably herein, can be used in the control system of the apparatus according to the second aspect of the invention. Any known or conceivable virtual three-dimensional representation of an object to be regulated so as to adjust the position and movement of the holding substrate and the physical object conforming to the virtual three-dimensional model of the object It can be used to operate a welding torch incorporating a wire feeder as constructed by fusing a continuous deposit of metallic material onto a holding substrate in a pattern that results in the construction of a Refers to a virtual three-dimensional representation. This involves virtual vectorization of the 3D model, for example, by first dividing the virtual 3D model into a set of virtual parallel layers and then dividing each of the parallel layers into a set of virtual quasi-1D pieces. It can be obtained by forming a layered model. The physical object is then deposited and fused onto the supporting substrate with a series of quasi-one-dimensional pieces of the metallic material feeder in a pattern according to the first layer of a virtual vectorized layered model of the object. It can be formed by involving a control system.

A second layer of the object is then formed by depositing and fusing a series of quasi-one-dimensional pieces of weldable material onto the previously deposited layers in a pattern that follows the second layer of a virtual vectorized layered model of the object. Repeat the sequence for 2 layers. The layer-by-layer deposition and fusion process continues to repeat for each successive layer of the virtual vectorized laminate model of the object until the entire object is formed. However, the invention is not bound to any particular CAD model and/or computer software implementing the control system of the apparatus according to the invention, nor is the invention bound to any particular type of control system. Build metal three-dimensional objects by solid freeform fabrication so long as the control system is adjusted to operate one or more melting tools, such as PAW torches, PTA torches, laser heat sources, or any combination thereof Any known or conceivable control system (CAD model, computer software, computer hardware, actuators, etc.) may be used. The jet devices provided herein can be used with those melting tools to achieve the grain refinement described herein.

As used herein, "high temperature material" refers to a material that is difficult to deform and exhibits low thermal expansion when exposed to temperatures above 400°C. Exemplary materials include titanium and titanium alloys.

As used herein, a "jet device" means a device that directly affects solidification, refinement, and inhibits grain growth across the sedimentary layer, global phase transformation, or any combination thereof. In order to do so, in situ refers to an article of manufacture that includes one or more nozzles that direct a cooling gas stream or cooling gas jet at, or any combination thereof.

As used herein, "in-situ" means that the manufactured product is not moving out of the deposition chamber and refers to the application of turbulent gas jets during the additive manufacturing process.

As used herein, "jet" refers to a stream of cooling gas ejected by a nozzle.

As used herein, "nozzle" refers to a projection with an opening that can regulate or direct the flow of cooling gas.

As used herein, "cooling gas" refers to a cooling gas applied to or across the weld pool surface to directly affect solidification and inhibit grain growth across the deposited layer. , or gas directed across the liquid-solid boundary, or onto the solidified metal near the solid-liquid boundary, or a combination thereof. The temperature of the gas can be any temperature that cools the surfaces with which the gas interacts. The temperature can be less than 100°C, or less than 50°C, or less than 30°C, or less than 25°C, or less than 10°C, or less than 5°C, or less than 0°C. Cryogenic gases can also be used. It has been found that the effects of gases cooler than room temperature have not been found to have significantly different effects than those achieved with room temperature gases.

B. Jet Device A jet device is provided herein. Jet devices are applied to the molten pool surface or across the molten pool or across the liquid-solid boundary to directly affect solidification of the molten metal and inhibit grain growth across the sedimentary layer. , or onto the solidifying metal near the liquid-solid boundary, or onto the solidifying metal, or any combination thereof. using a jetting device, to the molten pool surface, or across the molten pool, or across the liquid-solid boundary, or onto the solidifying metal in the vicinity of the liquid-solid boundary, or onto the solidifying metal, or both. Jet devices and systems and methods involving directing gas jets in any combination minimize or prevent directional solidification that forms the coarse elongated grain structure typical of conventional metal additive manufacturing processes. can do. Directional solidification in typical additive manufacturing processes is a result of the steep thermal gradients associated with typical additive manufacturing processes.

The present invention involves providing a jet device or combination of jet devices and utilizing a jet device or combination of jet devices, each jet device directly influencing the solidification of molten metal and the formation of a deposited layer. At or across the weld pool surface or liquid-solid boundary to inhibit grain growth across or improve the ability to control thermal conditions in additive manufacturing through the application of forced convection cooling. A plurality of jet nozzles are provided to direct the flow of cooling gas across or onto the solidifying metal near the liquid-solid boundary, or onto the solidifying metal, or any combination thereof. The jet device includes two separate conduits. The conduits can be connected by crosspieces to form a unitary body. A unitary construction can aid in positioning the jet device in relation to the melting tool. Nevertheless, the jet device can be provided as two separate segments. A separate segment is attached to the melting tool or wire feed, as described herein, using any fixture that provides the optimal position and angle for the gas jet from the device to impinge on the target area. It can be attached to a metallic material feeder, such as a feeder or metal powder feeder.

Each conduit, when joined separately or as a single piece, has one side, when the jet device delivers cooling gas to the melt pool or the region near the melt pool, to a piece of equipment comprising a melting tool, or One side is attached to the metallic material feeder when the jetting device delivers cooling gas to the solidifying material on the downstream side of the molten pool. The opposite side of each conduit includes one or more jet nozzles directed toward the workpiece and away from the melting tool. Each jet nozzle is connected to an opening in the conduit that delivers cooling gas through the conduit to enable fluid communication between the nozzle and the conduit so that the cooling gas can pass through the opening of each nozzle, and each nozzle is connected to the same. at or across the molten pool surface or across the liquid-solid boundary, such as in the elementary transformation zone or region where precipitation reactions occur that order the alloying constituents to form secondary phase particles, or It can be directed separately to predetermined locations, such as onto the solidified metal near the liquid-solid boundary or onto the solidified metal beyond the solid-liquid boundary. In some configurations, the nozzle is positioned in the molten pool surface, across the molten pool, across the liquid-solid boundary, on solidified metal near the liquid-solid boundary, and on solidified metal beyond the solid-liquid boundary. The cooling gas flow can be directed to two or more points selected from . Each conduit has a fluid connector at one end. A fluid connector allows the conduit to be connected to a cooling gas source. The opposite end of the conduit is sealed. The diameter of the conduit is larger than the opening to which each nozzle is attached. For example, the diameter of the nozzle can range from about 1 to about 10 mm, while the diameter of the opening or apertures attached to the nozzle can range from about 0.5 to about 5 mm. In some configurations, the nozzle and opening diameters are the same and can range from about 0.5 to about 5 mm, or from about 1 to about 3 mm. The total number of nozzles is limited only by the space constraints where the jetting devices are mounted. In some configurations, the number of nozzles can be from about 4 to about 24. Instead of individual nozzles, a continuous gas diffuser or grid designed to create a directed turbulent flow of cooling gas can also be used as the gas outlet of the spout device.

Each conduit provides cooling gas to a nozzle or set of nozzles attached to the conduit. Each conduit may be branched or include channels, or may include pipes, tubes, or lines for individually delivering separate cooling gas streams to each nozzle. The nozzles in each conduit can be arranged in rows, with each row containing 1, 2, 3, or 4 nozzles. The nozzles can be configured to allow individual adjustment of gas flow to each nozzle or separate gas flows into different sets of nozzles.

One or both conduits may contain one or more sensors. The conduit may include a flow meter that allows the flow of gas through the conduit to be measured. Any flow meter known in the art can be used with the system. The flow meter may be a paddle wheel flow meter, turbine flow meter, magnetic flow meter, optical sensor, electromagnetic velocity sensor, Coriolis force flow meter, thermal flow meter, ultrasonic flow meter, or others known in the art. Any type of flow meter can be included. Examples of flow meters known in the art are US Pat. No. 4,422,338 (Smith, 1983), US Pat. No. 4,838,127 (Herremans et al, 1989) US Pat. No. 5,594,181 (Strange, 1997), US Pat. No. 7,707,898 (Oddie, 2010), and US Pat. No. 7,730,777 (Anzal et al. , 2010). In some configurations, the conduit can include notches, recesses or protrusions for placement or attachment of the flow meter.

The conduit may include a temperature sensor that allows measurement of the temperature of the conduit or the temperature of the cooling gas within the conduit, or both. Any temperature sensor known in the art can be used. Exemplary temperature sensors include thermocouples, resistance temperature detectors, thermistors, infrared thermometers, bimetallic devices, liquid expansion devices, and combinations thereof. In some configurations, the conduit can include notches, recesses or protrusions for placement or attachment of temperature sensors.

The jet device can also include one or more temperature sensors for measuring the temperature of the workpiece. In some configurations, a jetting device configured to direct a jet of cooling gas at or in close proximity to the weld pool includes a temperature sensor directed at the surface of the workpiece, the surface of the weld pool, or a combination thereof. can include A jetting device configured to direct a jet of cooling gas toward a solidified metal region of the workpiece, such as an allotropic transformation zone, is used to measure and/or control the cooling rate over the relevant temperature region. a first temperature sensor directed at the surface of the workpiece ahead of the area impinged by the gas jet or exposed to the cooling gas jet and after the area impinged by the cooling gas jet or exposed to the cooling gas jet. and a second temperature sensor directed toward the surface of the workpiece. The apparatus may include a temperature sensor directed at the post-solidification zone immediately after solidification of the molten pool. The apparatus may include a temperature sensor directed into the post-transformation zone, where cooling of the deposited solidified metal may cause allotropic transformations or other thermochemical reactions. Any temperature sensor known in the art can be used, especially a non-contact temperature sensor. Exemplary temperature sensors include infrared thermometers and infrared pyrometers. In some configurations, the conduit can include one or more notches, recesses or protrusions for placement or attachment of temperature sensors. The conduit can be made of or include a high temperature resistant material. Exemplary high temperature materials include titanium and titanium alloys, tungsten and tungsten alloys, stainless steel, Inconel alloys, and alloys containing chromium and nickel, such as Hastelloy alloys, as well as nickel, iron, cobalt, copper, molybdenum, tantalum, Alloys containing two or more of tungsten and titanium are included. In some configurations, the conduit is made of titanium or a titanium alloy containing Ti in combination with one or a combination of Al, V, Sn, Zr, Mo, Nb, Cr, W, Si, and Mn. be done. In some configurations, the conduit is made of Ti-6Al-4V alloy.

Each conduit has a plurality of jet nozzles configured to be angled opposite the direction of travel toward the trailing edge of the melt pool created by the melter and additional feedstock material. can be included on the side. The nozzle may be positioned at the surface of the molten pool, or across the molten pool, or across the liquid-solid boundary, or onto the solidifying metal near the liquid-solid boundary, or onto the solidifying metal beyond the liquid-solid boundary, and so on. , directs a turbulent flow of cooling gas at a predetermined point. Each nozzle has an angle formed between the nozzle and the conduit that is less than 80°, or less than 70°, or less than 60°, or less than 50°, or less than 40°, or less than 90°, such as less than 30°. It can be positioned at any angle to the conduit such that A preferred range of angles is from about 70° to about 30° from horizontal. The nozzle may be configured and positioned to prevent blowing of the cooling gas toward the melting tool, such as a torch, which could disrupt the arc or melt the consumable electrode or metal wire. can reduce the efficiency of the ability of

The jet nozzle can have any shape. In some configurations, the nozzle is configured to be tubular, having a cylindrical shape. The nozzle can have a rectangular, hexagonal, octagonal, oval, or asymmetrical shape. The cross section of the nozzle can be of any shape. Exemplary shapes for nozzle cross-sectional openings include circular, oval, oval, square, rectangular, diamond, hexagonal, and octagonal. Non-uniform or asymmetric cross-sections can be selected to promote turbulence of the gas exiting the nozzle.

The wall thickness of the nozzle is thick enough to withstand the pressure of the cooling gas flowing through the nozzle. The wall thickness can also be selected to minimize thermal distortion at temperatures to which the spouting device may be exposed during additive manufacturing processes. For example, the nozzle wall thickness can be in the range of about 0.25 to about 5 mm, or about 0.5 to about 3 mm.

The nozzle includes an orifice through which cooling gas flows toward the workpiece. The gas nozzle orifice can have any geometry or shape. Orifices can be circular, oval, square, rectangular, diamond, hexagonal, or octagonal. A non-uniform or asymmetric cross-section of the orifice can be selected to promote turbulence of the gas exiting the nozzle. The nozzle orifice can have a diameter of about 0.5 to about 5 mm, or about 1 to about 3 mm. The diameter of the orifice can be the same diameter as or smaller than the inner diameter of the nozzle. If the diameter of the orifice of the nozzle is smaller than the inner diameter of the nozzle, the velocity of the gas exiting the orifice can be higher than the velocity of the gas in the conduit. The nozzle can include multiple orifices.

Cooling gas enters the jet device through the inlet of each conduit and exits the jet device through each of the nozzles. Each nozzle can deliver a cooling gas source to a set of nozzles. Each conduit may be bifurcated or may include channels for individually delivering separate cooling gas streams to each nozzle. The maximum flow rate of gas delivered to the jetting device should typically be about 500 L/min, or 400 L/min, or 300 L/min, or 200 L/min, depending on the configuration and placement of the cooling jet device. can be done. For example, for a jet device that delivers a jet of cooling gas that impinges on the surface of the weld pool, the turbulent gas flow should not deform the molten metal applied through the melting tool or its application path, or into a string. The cooling gas flow rate can be selected so as not to splash and destabilize the applied molten metal or adversely affect the stability or shape of the weld pool. The cooling gas flow rate can range from about 1 L/min to about 150 L/min, typically from about 5 L/min to about 100 L/min. The minimum flow rate to effectively achieve a grain refinement effect is typically 10 L/min, depending on the material to be processed and the design of the jetting device. In configurations where the flow of cooling gas to each nozzle can be controlled separately, more cooling gas flow can be directed to the metal in the solidified state as compared to the metal in the molten pool. The flow rate of cooling gas applied in situ to the material in its deposited and solidified state can be significantly higher than the gas flow directed into the weld pool. In these cooling jet devices, the flow rate of cooling gas directed in situ at the surface of the material in its deposited and solidified state can be up to 500 L/min. A separate gas supply can be connected to each cooling jet to allow separate control of the gas flow rate from the nozzle of the jet. For example, a first gas supply provides cooling gas to a jet device directed at or near the weld pool and a second gas supply is directed at the material in its deposited and solidified state. connected to a jet device. Each gas supply can include a regulator that can be adjusted manually or automatically, such as by computer control, to regulate the flow rate of gas supplied to a cooling jet device connected to a conduit connected to the regulator. . In configurations where the jet device includes multiple separate conduits, each conduit of the device can be connected to a separate regulator so that the flow of cooling gas to each conduit can be controlled separately.

Cooling gas can be provided as a steady flow from a nozzle. The cooling gas can be provided intermittently or in pulses from the nozzles. The intermittent or pulsating flow of cooling gas can help dissipate thermal energy from the impingement region of the cooling gas. Providing gas intermittently can be accomplished by using a valve switch. Pulsatile flow refers to a time-varying gas flow rate without limitation with respect to magnitude, phase, and other characteristics of the time-varying phenomenon. Pulsating flow typically involves continuous cycling of multiple different gas flow rates that vary over time. The pulsing of the gas is performed over a period of time such that time-varying high and low flow conditions are exhibited. The pulsatile flow of gas can be provided using any method or apparatus known in the art (e.g., US Pat. No. 5,954,092 (Kroutil et al, 1999); See U.S. Patent No. 6,679,278 (Lemoine et al, 2004) and U.S. Patent No. 9,566,554 (Wue et al, 2017).

Each conduit may include at least one nozzle, so that at least two nozzles are located at or across the melt pool surface, or across the liquid-solid boundary, or at the solid-liquid boundary. Cooling gas is directed onto nearby solidified metal, onto solidified metal beyond the solid-liquid boundary, or any combination thereof. The total number of nozzles present in the jet device can be a different number depending on the desired configuration. In some configurations, the jet device has a total number of 2-24 nozzles. The number of nozzles in each conduit can be the same or different. For example, each conduit may contain ten nozzles, resulting in a jet device with twenty nozzles. In another example, one conduit could have 8 nozzles and the other conduit could have 12 nozzles, resulting in a jet device with 20 nozzles, but this jet The device has a different configuration than the first jet device, which had ten nozzles in each conduit.

The number, configuration, and spacing of the nozzles can be selected such that the coverage by the cooling gas ejected from the nozzles covers the desired length of the workpiece to be formed. For example, for high deposition rate processes, such as plasma and wire-based systems, the number of nozzles and nozzle configurations may range from about 5 mm to about 50 mm, or from about 10 mm to about 40 mm, or from about 15 mm to about 30 mm along the direction of travel. can be selected to deliver cooling gas covering a length of . The nozzle may be configured to deliver cooling gas covering a length of approximately 20 mm along the direction of travel.

The length of each nozzle can be the same length, or different nozzles can have different lengths. Typically, each nozzle can have a length sufficient to produce a directional flow from the orifice. For example, the length can be in the range of about 2.5mm to about 25mm, or about 5mm to 20mm. The length of each nozzle and the location of each nozzle can be selected to apply a flow of cooling gas across the deposited molten material. The nozzles can be provided in pairs or groups, with the length of each nozzle and the position of each nozzle being such that one member of the pair, or several members of the group, impinge on the cooling gas at one point. and the other member of the pair, or other member of the group, is selected to provide a configuration that directs the cooling gas elsewhere. For example, one group of nozzles can be directed at the melt pool surface, while another group of nozzles can be directed at the solidified material.

The number, configuration and spacing of nozzles may be selected to promote turbulent gas flow in the vicinity of the surface of the molten pool, or the liquid-solid boundary, or the solidifying metal in the vicinity of the liquid-solid boundary, or any combination thereof. can. For example, the nozzles can be positioned such that jets of cooling gas from at least two nozzles collide with each other to create turbulence. One or more of the nozzles may include protrusions or depressions in the nozzle orifice or in the nozzle body or a combination thereof to disrupt laminar flow of the cooling gas and promote turbulent flow. Also, the velocity of the cooling gas flowing through the nozzle can be monitored and adjusted so that the cooling fluid exiting the nozzle exhibits turbulent rather than laminar flow. Turbulence can be created during the interaction of impinging gas jets with a laminar boundary layer near the workpiece. The cooling effect is enhanced by the turbulence of the cooling gas. The conduit may include one or more baffles in the cooling gas flowpath. The gas striking the baffle can convert the directional kinetic energy induced by the impact upon impact with the baffle into rotational energy resulting in turbulent mixing or turbulence.

Insulating material can be used to insulate the jet device from the melting tool or molten pool or metallic material feeder or any combination thereof. The insulating material can be positioned between the jet device and the melting tool, between the jet device and the metal material feeder, or on the surface of the jet device facing the weld pool of the workpiece.

The insulating material can include any material suitable for use at temperatures near the plasma arc, laser system, or weld pool. The insulating material can be or contain a thermal insulating ceramic. Such ceramics are known in the art and may include oxides or nitrides of Al, B, Zr, Mg, Y, Ca, Si, Ce, In, and Sn, and combinations thereof. (e.g., U.S. Pat. No. 6,344,287 (Celik et al., 2002), U.S. Pat. No. 4,540,879 (Haerther et al., 1985), and U.S. Pat. No. 7, 892,597 (Hooker et al., 2011)). The insulating material can be or include aluminum nitride, aluminum oxide, magnesium nitride, magnesium oxide, quartz, silicon nitride, boron nitride, or zirconium dioxide, or mixtures or combinations thereof.

A perspective front view of an exemplary embodiment of a jetting device configured for delivery of gas jets to a weld pool is shown in FIG. The direction of travel of the workpiece is represented by an arrow (in this example, the direction of travel depicted is toward the viewer). The jetting device 100 depicted in the figures includes a first conduit 10 that includes on one side five pairs of nozzles 25 that direct gas jets 30 toward a deposited string 95 of workpieces and a melt pool 90 . The illustrated jetting apparatus also includes a second conduit 60 that includes five pairs of nozzles 75 that direct the gas jets 80 toward the deposited string 95 of workpieces and the melt pool 90 . The jet device 100 directs jets of cooling gas at the free surface of the weld pool and the liquid-solid interface as the molten material is deposited to form the string 95 . A cooling gas supply 40 provides cooling gas to the first conduit inlet 15 . Cooling gas supply 50 provides cooling gas to second conduit inlet 65 . A similar configuration of conduits and nozzles exists on the opposite side of the melting tool 200, although only the gas jet is visible in the figure.

In a typical configuration, the melting tool can be located above the molten pool and the wire or powder feedstock is fed into the molten pool or into the melting arc or beam. The spouting device also has nozzles so that each conduit of the spouting device is mounted on either side of the melting tool and directs the jet of cooling gas at the molten pool free surface or at the boundary between the liquid molten material and the solid molten material. can be positioned so that the

A partially cut-away side view of an exemplary configuration of a jetting device configured for delivery of gas jets to a weld pool is shown in FIG. The jet device depicted includes a first conduit 10 containing a group of nozzles 25 and a second conduit 60 containing a group of nozzles 75 . A similar configuration occurs on the opposite side of melting tool 200 to which the jet device is attached. The jet arrangement shown shows that the conduits on both sides of the melting tool are connected by a crosspiece 85 to form a unitary body. Also shown in FIG. 2 are an internal diffuser 20 in conduit 10 and a diffuser 70 in conduit 60, which can help equalize gas pressure and flow from the nozzle. . Gray lines 30 and 80 represent the gas jet directions from nozzles 25 and 75, respectively. Cooling gas is provided to conduit 10 through inlet 15 and delivered to conduit 60 through inlet 65 . Also shown in FIG. 2 is a wire feeder 300 that feeds a metal wire 350 to a position above the weld pool 90 .

The application of cooling gas as gas jets 30 and 80 from the jetting device to the molten pool 90, or to the interface between the liquid and solid molten materials, or both, nucleates and removes from the molten pool free surface. Propagating opposing solidification fronts can help form a top cap of finer grains that inhibits the continued growth of directional grains across the layer. This effect can be more pronounced in high deposition rate processes, where the solidification rate is typically lower, and the directional solidification front is farther than the depth at which the top cap is formed and remelted by a continuous layer. Move slowly enough to propagate to This mechanism is illustrated in FIG.

As illustrated in FIG. 3, on the far left, deposition of metal during conventional additive manufacturing results in a coarse grain structure in the solidified state and can exhibit columnar crystal growth. Depending on the alloy, the resulting grain structure can be elongated with a high aspect ratio. This is typically due to the directional heat removal provided by the relatively cool workpieces when superheated molten metal is applied to the workpieces in the string. In these conventional processes, the occurrence of solidification begins in the previously deposited metal layer and propagates through the deposited material as the deposited layer cools. The grain structure in the solidified state can often extend across several layers and can grow up to several centimeters in size. These properties typically adversely affect mechanical properties, resulting in reduced and/or anisotropic strength, elongation, and fatigue performance.

The jet devices provided herein deliver cooling gas. The cooling gas delivered by the cooling jet device can be any gas that does not interfere with the welding process used to deposit the molten metal to form the string during additive manufacturing. Exemplary cooling gases include argon, helium, neon, xenon, krypton, and blends thereof. Typically, the cooling gas contains argon alone or in combination with another gas. The temperature of the cooling gas delivered to the inlet of the spouting device is typically less than 100°C, or less than 80°C, or less than 60°C, or less than 40°C, or less than 25°C. The cooling gas may be delivered to the inlet of the jet device at a temperature below about room temperature, such as below about 25°C, or below about 20°C, or below about 15°C, or below about 10°C. The cooling gas can be delivered to the inlet of the jet device at a temperature of about -195°C to about 25°C. Application of a cooling gas to the molten pool by means of a jet device, or to the liquid-solid boundary as the molten material cools, or both, results in efficient refinement of the metal grains. and produce finer grains than those obtained when no cooling gas is applied.

The application of cooling gas from the jet device to the molten pool, or to the liquid-solid boundary as the molten material cools, or both, is also typically present using conventional additive manufacturing techniques. It can help reduce temperature gradients across the directional solidification front. Reducing the temperature gradient at the directional solidification front can destabilize continuous propagation due to the cooling effect of the cooling gas applied to the free weld pool surface.

The application of cooling gas from the jetting device to the molten pool, or to the liquid-solid boundary as the molten material cools, or both, also provides cooling to the material in the solidified state adjacent to the liquid-solid boundary. The effect can help change the direction of coagulation. Application of a cooling gas can alter the heat removal from the trailing edge of the weld pool. Application of a cooling gas can also increase the overall solidification rate. The formation of columnar grain structures is minimized or prevented as a result of the mechanisms detailed above. Grain refinement is an effect facilitated by the application of cooling gas by the spouting device provided herein. As a result of the application of the cooling gas by the spouting devices provided herein, grain refinement is promoted, such as the formation of a substantially equiaxed grain structure, which improves the mechanical properties of the manufactured product.

To maximize the effectiveness of the jet device, other process parameters are typically such that a certain length of the weld pool is maintained for gas jet impingement and temperature gradients in the workpiece are minimized. It is set to promote fracture of the solidification front by controlling the processing temperature and energy input so as to be suppressed. For example, processing temperatures are typically maintained within the range of about 300° C. to about 750° C., depending on which alloy is utilized. The energy input also depends on which alloy is used. The effective energy input for Ti-6Al-4V in high deposition rate plasma and wire-based processes can typically be from about 300 J/mm to about 1000 J/mm. Thermal gradients in the workpiece can be minimized by processing at higher workpiece temperatures (interpass temperatures) and with lower energy input per unit length.

Elimination of the coarse columnar solidification structures that characteristically occur during additive manufacturing is a key to achieving an optimal balance of strength, ductility and fatigue properties in additively manufactured products, including titanium-based products such as Ti-6Al-4V products. expected to be beneficial to Manipulating the weld pool conditions, such as by directing a jet of cooling gas at the liquid-solid boundary of the weld pool using the jet apparatus provided herein, induces opposing solidification fronts at the free surface of the weld pool. to accelerate. This can reduce or largely eliminate the formation of elongated columnar structures, which can impose a limit on the number of desirable grain variations that can occur, thereby increasing the diversity of crystal orientations in the deposited material. Let

During additive manufacturing, the deposited material undergoes temperature changes from the molten pool through the solidified crystalline region to the solidified metal region and the microstructural transition region. Thus, manipulating conditions throughout the deposition process in addition to the weld pool, such as by controlling or manipulating the cooling rate in the metal solidification region or the metal transition region, or both, promotes the formation of the desired microstructure. be able to. Depending on the alloy, the crystallinity and morphology of the microstructures formed by allotropic transformations or other mechanisms may result in different crystallographic directions in the alloy lattice as the deposited material cools and undergoes solidification and solid phase transformations. The grain structure in the solidified state can be influenced by orientation relationships, grain boundary nucleation and alignment due to interfacial energies, diffusion rates and thermal conductivity differences between them. Differences in thermal history can lead to significant differences in strain response at different grain boundaries in many alloys.

The jet apparatus provided herein can be used to control or adjust the cooling rate throughout the deposition process, thereby influencing the thermal history of parts produced by additive manufacturing. Forced cooling by concentrated turbulence of jets of cooling gas applied to materials in the solidified state using jet devices to control heat transfer, thermal conductivity, thermal energy dissipation, and solid phase transition. can be done. The jet device can achieve localized cooling and temperature measurement at target areas of the deposit between string depositions to precondition and uniform the temperature of the workpiece during successive layer formation.

A side view of an exemplary configuration of a jetting device configured to deliver a gas jet to a solidifying metal region is shown in FIG. The depicted embodiment of the cooling jet device 500 includes a plurality of nozzles 525 that generate cooling gas jets 530 and are attached to one side of the wire feeder 300 . A similar configuration can occur on the opposite side of the wire feeder 300 to which the jetting device is attached. In an alternative embodiment, one or more rows of nozzles can be present on the lower surface of the wire feeder to which the jetting device is attached. In an alternative embodiment, the jet device can include a U-shaped conduit parallel or nearly parallel to the workpiece, the arms of the U-shaped conduit can be located on either side of the shaped string of the workpiece, and It includes a nozzle directed downward toward the workpiece. The nozzles can be directed such that the cooling gas jet 530 impinges on the top surface of the workpiece, or the side surfaces of the workpiece, or both the top surface and at least one side surface of the workpiece. In an alternative embodiment, the jet device may include a trifurcated or Ψ-shaped conduit parallel or nearly parallel to the workpiece (a U-shaped conduit branching into separate conduits parallel to the arms of the U) and side arms includes a nozzle located on one side of the formed string of the workpiece and directed downward toward the top surface of the formed string or the side of the formed string, and a central conduit directed downward toward the top surface of the formed string of the workpiece. including a nozzle directed toward the In an alternative embodiment, the jet device may include three separate conduits in parallel, each conduit with its own gas supply. One outer conduit may include nozzles directed to one side of the deposition string, the other outer conduit may include nozzles directed to the other side of the deposition string, and the central conduit may comprise: A nozzle directed toward the top surface of the deposition string may be included. The positioning of the sensor and jet device can be adjusted depending on the target temperature range considered important in determining and effecting the cooling rate. Positioning can therefore be adjusted based on the metal alloy to be deposited.

Also shown in FIG. 7 is a temperature sensor 550 mounted to allow temperature readings to be taken on the workpiece surface in front of the zone of application of the jet of cooling gas. Also shown in FIG. 7 is a temperature sensor 560 mounted behind the jetting device 500 to allow temperature readings to be taken on the workpiece surface after application of the jet of cooling gas. The direction of travel of the workpiece is represented by arrow D (in this example, the direction of travel of the depicted workpiece is from left to right). In the embodiment depicted in Figure 7, the cooling jet device 500 and temperature sensors 550, 560 are shown connected to the wire feeder 300, but such attachment is merely exemplary. A cooling jet device 500 and a cooling jet device 500 are included in one or more components of the system to enable movement with the melting tool 200, application of cooling gas to desired surfaces of the workpiece, and appropriate temperature measurement of the workpiece. Separate brackets or mounting arms can be used to mount either temperature sensor 550,560. The gas jets are directed so as not to impede the movement of the molten pool or metal and to provide cooling by gas flow backward along the deposition string. Application of a cooling gas to the solidifying metal can achieve suitable localized cooling for a period of time determined by temperature readings from temperature sensors, thereby providing continuous control of the cooling rate during material addition and between string depositions. Local preconditioning can be achieved. The flow rate of the cooling gas jet from the jetting device directed at the region of the solidified metal workpiece behind the weld pool is received by in-situ measurements or from temperature sensors before and after the impingement region of the cooling gas jet. Based on the readings taken, adjustments can be made based on the thermal conditions of the workpiece being processed by following a preprogrammed computer controlled schedule. Suitable cooling can be achieved by applying a flow of cooling gas for a period of time that can be determined by data received from temperature sensors before and after the region of impingement of the cooling gas. The positioning of the temperature sensor and jet device can depend on which temperature regions of the workpiece are most important to capture and affect the cooling rate. Positioning can be adjusted based on the metal alloy to be deposited.

The jet device allows continuous control of the cooling rate during material addition and preconditioning between string depositions without terminating the deposition process. The flow rate may be adjusted manually by monitoring data from the temperature sensor or automatically using a computer that receives temperature data from the temperature and adjusts the flow rate or duration or both to achieve the target cooling rate. Adjustments can be made based on changes in the thermal conditions of the workpiece during processing. The infrared temperature sensor can be selected and calibrated for the relevant temperature range of the deposition process to which the workpiece will be subjected. Sensor data can be measured and stored at rates of 1 Hz or higher. Temperature data may be captured by a computer in a process control system to enable in-process feedback control of the deposition process or viewed post-process manually as part of the iterative deposit development stage to generate a deposition schedule. or a combination of these techniques. The flow can be zero or near zero in the first deposited layer and then increased as residual heat builds up. Flow rates can range from zero or near zero up to about 500 L/min. The flow rate can range from zero or near zero up to about 400 L/min. The flow rate can range from zero or near zero up to about 300 L/min. In some applications, the cooling gas flow rate is at least 10 L/min, or at least 25 L/min, or at least 50 L/min, or at least 100 L/min, or at least 150 L/min, or at least 200 L/min, or at least 250 L/min. min, or at least 300 L/min, or at least 350 L/min, or at least 400 L/min, or 500 L/min or less, or 450 L/min or less, or 400 L/min or less, or 350 L/min or less, or 300 L/min or less; or 250 L/min or less, or 200 L/min or less, or 250 L/min or less, or 200 L/min or less, or 150 L/min or less, or 100 L/min or less, or 50 L/min or less. The cooling gas can be inert or non-inert, depending on the requirements of the alloy to be processed. The cooling gas can be an elemental gas or a mixture of different gases.

The jet device can apply suitable cooling to these areas over a period of time to effectively remove the excess thermal energy imparted during deposition. The jet device applies cooling gas directly onto the deposited metal while deposition is taking place to achieve local cooling rate control as well as local cooling rate and temperature measurement at the deposition region of the deposition string. preconditioning and/or uniformity of workpiece temperature during continuous layer formation. A high velocity cooling gas can be delivered by a jet device to a region of a continuous layer of deposited material.

In conventional welding processes, to protect the deposited material from the ambient atmosphere and to avoid contamination of the weld metal, a shielding gas device that follows the welding torch is applied to create a laminar gas curtain of the solidifying material. can be directed. This laminar flow of gas is insufficient to affect or control the temperature dissipation or cooling rate. The jetting device provided herein applies a jet of cooling gas at a flow rate sufficient to create turbulence in the gas. A turbulent flow of the cooling gas from the jet device nozzle can typically be achieved by a high velocity of the cooling gas through the nozzle.

C. Systems Typical additive manufacturing techniques, especially high deposition rate processes, can often result in large variations in processing conditions due to variations in deposit geometry. Local workpiece temperatures of larger deposits with longer repetition intervals (i.e., longer time per layer) can cause strings to be made in rapid succession and heat build up. They have very different temperature conditions compared to smaller deposits. Similarly, the local mass input can determine or effect the profile of heat removal from the deposited material, and the adjacent mass affects the heatsink's ability to handle additional thermal energy. influence.

These factors can lead to non-optimal and varying material properties. Post-process heat treatments beyond basic stress relief are often difficult to achieve or ineffective for many metal alloys. Importantly, a fully formed deposit may have a cross-sectional thickness that does not allow bulk heat treatment to achieve the desired cooling rate. The system for constructing metal objects by additive manufacturing provided herein overcomes these deficiencies of prior art systems. The piece-by-piece additive manufacturing method utilizing jet devices provided herein can allow for cooling rate control in individual strings of small quantities of material that make up the final part during the deposition process. The system is flexible and highly controllable and provides a way to improve the consistency of metal additive manufacturing products, especially for large scale high deposition rate processes. The system can include a computer that can be used to automate part or all of the system. A computer can communicate with the control system and can be used to read the design model. The computer can collect data, store and/or manipulate data such as flow rates and temperatures, or other parameters of the manufacturing process. A computer can use the collected data to operate or modify the manufacturing process. A computer can include a computer processor that can communicate with one or more of the components of the system.

As the deposited string solidifies and cools, most relevant alloys undergo significant solid phase transformations that can have a large impact on material properties. One example is an allotropic modification in which one crystal structure arrangement changes to another crystal structure arrangement. Many titanium alloys exhibit an allotropic transformation in the temperature range of 1050°C to 800°C during cooling. For many steels, the temperature range for transformation during cooling is typically 800°C to 400°C. Another example of a solid state transformation of deposited metal during cooling is a precipitation reaction in which secondary phase particles are formed due to ordering of alloying constituents. As an example, nickel-based superalloys can exhibit precipitation reactions during cooling from about 1000°C to 700°C and during long dwells above 600°C. Grain growth during long-term residence at high temperature also affects the properties of most alloys. The spouting device provided herein affects or controls the cooling rate, thereby enabling modification of the properties of the deposited material, resulting in improved consistency of the metal additive manufacturing product. resulting in an improvement in The system provided herein allows for continuous control of cooling rate during material addition and local pre-adjustment between string depositions. The system provided herein allows control of processing conditions for a manageable amount of individual string segments. The system allows for temperature control during deposition, achieving results not possible with the use of post-process heat treatments, which makes it more difficult to control the cooling rate of the thicker sections of the full additive manufacturing deposit. , and the high cooling rates achievable using the jet apparatus provided herein are not achievable using post-process heat treatment without using less practical methods such as water or oil quenching. do not have.

Systems provided herein include a melting tool for melting a source of metal into droplets of metallic molten material that are deposited in a liquid pool on a base material and across the liquid pool, or For directing the cooling gas to impinge on the liquid weld pool, or on the solidifying material adjacent to the liquid-solid boundary of the liquid weld pool, or any combination thereof, as provided herein. design, such as a computer-aided design (CAD) model of a jet device, a supply of cooling gas, a system for positioning and moving the preform with respect to the heating device and jet device, and a metal object to be formed; Loading the model, using the design model to adjust the position and movement of the system for positioning and moving the base material, and creating a physical object by fusing a continuous deposit of metallic material onto the base material. and a control system capable of operating the heating device and the jet device such that a

A single melting tool can be used, or a two-gun system with two melting tools can be used. The deposition rate of molten metal on the forming work piece is such that the first gun preheats the base material to form a preheat zone and the second gun heats and melts the metal on the preheat zone of the base material. It has been found that it can be increased using the two-gun system used. The first gun can ensure fusion between the base material or workpiece and the molten metal caused by the action of the second gun on the metal, such as metal wire or metal powder. The first gun can deepen the penetration of the molten metal into the preheated region of the base material. The droplet superheating of the molten metal can maintain a molten pool in the vicinity of the preheated zone of the base metal. Preheating the matrix results in better wettability, better deposition profile, and increased deposition rate. With respect to the deposition profile, it is possible to obtain a rounder and wider deposition profile by preheating the substrate. An improved profile can result in a profile with a beneficial angle to the base material that can facilitate fusion to the base material and prior metal deposition. Improved fusion results in a manufactured product with improved integrity.

Each gun contains a melting tool. Each gun can be controlled separately, and each gun can be adjusted to provide separate temperature effects. The advantage of this arrangement is that the amount of heat energy imparted to the metal feedstock to be melted in the preheating zone of the work piece can be greater than the amount of energy imparted to the work piece, avoiding overheating of the work piece. That is.

In the two-gun additive manufacturing system embodiments provided herein, the system can include a torch (PAW, PTA, GMAW or MIG type) or a laser device or any combination thereof as a melting tool. In some configurations, a first torch preheats a target deposition area on the workpiece to form a preheated area, and a second torch heats and melts the consumable electrode, resulting in a liquid of molten metal. A droplet falls on a preheated area of the target deposition area. In some configurations, the laser device preheats the target deposition area on the substrate to form the preheated area, and the torch heats and melts the consumable electrode, resulting in droplets of molten metal on the target deposition area. fall into the preheating area. In some configurations, the torch preheats the target deposition area on the base material to form the preheated area, and the laser device heats and melts the metal wire, resulting in droplets of molten metal on the target deposition area. fall into the preheating area.

A laser or torch can be arranged to direct thermal energy (e.g., laser energy or a plasma-transferred arc, respectively) to the target area of the workpiece to form the preheat zone, and the torch or laser can may be arranged to direct thermal energy to the consumable electrode or the end of the metal wire positioned above the preheated region of the base material. The thermal energy melts the end of the consumable electrode or metal wire to form droplets of molten metal that fall onto the preheated region of the base material beneath the end of the consumable electrode or metal wire. A melting tool that directs thermal energy to a target deposition area promotes fusion between the base material and the molten metal material deposited on the base material by deepening the penetration of the molten metal droplets into the base material. can be done. The consumable electrode or melting tool used to melt the metal wire also contributes thermal energy in the vicinity of the preheat zone of the target deposition area which contributes to the thermal energy provided by the melting tool directed at the base material. be able to. The droplet superheating of the molten metal can help maintain the weld pool in the vicinity of the preheated zone of the base metal.

Is the consumable electrode or metal wire Al, Cr, Cu, Fe, Hf, Sn, Mn, Mo, Ni, Nb, Si, Ta, Ti, V, W, or Zr, or composites or alloys thereof? or Al, Cr, Cu, Fe, Hf, Sn, Mn, Mo, Ni, Nb, Si, Ta, Ti, V, W, or Zr, or composites or alloys thereof. In some embodiments, the consumable electrode is a wire containing Ti or a Ti alloy. The consumable electrode or metal wire is or is a titanium alloy containing Ti in combination with one or a combination of Al, V, Sn, Zr, Mo, Nb, Cr, W, Si, and Mn can contain For example, exemplary titanium alloys include Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2Nb-2Cr, Ti -47Al-2W-0.5Si, Ti-47Al-2Nb-lMn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3Si. Consumable electrodes or metal wires can contain aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, alloys thereof, and combinations thereof. can.

A typical cross-section of a consumable electrode or metal wire is a circular cross-section. The diameter of the consumable electrode or metal wire can be up to about 10 mm and can be within the range of about 0.8 mm to about 5 mm. The consumable electrode or metal wire can have practically achievable cross-sectional dimensions such as, for example, 1.0 mm, 1.6 mm, and 2.4 mm, or from about 0.5 to about 3 mm. The feed rate and positioning of the consumable electrode or metal wire is such that the consumable electrode or metal wire is continuously heated when it reaches the intended position above the molten pool of the base metal. It can be controlled and regulated according to the efficiency of the power supply to the PTA torch or laser device or both to ensure that it is melted.

The laser device can generate a laser beam of sufficient thermal energy to transfer thermal energy to the work piece to preheat regions of the work piece or to melt the metal wire. Preheating the base material with energy from the laser beam promotes fusion between the base material and the molten metal material by deepening the penetration into the base material. In some embodiments, at least a portion of the preform can be melted by energy from a laser beam of a laser device. In some embodiments, the laser beam of the laser device applies sufficient heat to form a molten pool in the base material at the location where the metallic material generated by the PTA torch or another laser is to be deposited.

Examples of suitable laser devices include ytterbium (Yb) lasers, Yb fiber lasers, Yb fiber-coupled diode lasers, Yb:glass lasers, diode-pumped Yb:YAG lasers, neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, CO ₂ laser, CO laser, Nd: glass laser, neodymium-doped yttrium orthovanadate (Nd:YVO) laser, Cr: ruby laser, diode laser, diode pumped laser, excimer laser, gas laser, semiconductor laser, solid state laser, dye laser, X-ray lasers, free electron lasers, ion lasers, gas mixture lasers, chemical lasers, and combinations thereof. Preferred lasers include Yb lasers, especially Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers can have low reflectivity compared to other laser wavelengths.

The torch is used to heat and melt consumable electrodes such as gas metal arc welding (GMAW), especially welding that uses a non-reactive gas to form the arc (metal inert gas welding or MIG welding), or to It can have any configuration capable of producing an electric arc to heat a target area on the material. Thus, the torch can be a PAW torch, a PTA torch, a GMAW torch, or a MIG type torch. A consumable electrode is melted in a plasma produced by a torch using an electric arc, and the molten consumable electrode is deposited in a molten pool on the workpiece and applied to the metal object to form a near net shape metal. form an object. Preheating the base material with energy from the torch promotes fusion between the base material and the molten metal material by deepening the penetration into the base material. In some embodiments, at least a portion of the base material can be melted by energy from the plasma of the torch. In some embodiments, the plasma of the torch applies sufficient heat to form a weld pool in the base material at the location where the metal material melted by the different torch or laser device is to be deposited.

supplying heat to the substrate by using a first melting tool for preheating the substrate to form a preheated zone and a second melting tool for melting the consumable electrode or metal wire; The advantage is that it is possible to increase the thermal energy directed to the consumable electrode or metal wire independently. The melting force applied to the consumable electrode or metal wire is controlled by the mass input (melting of the consumable electrode or metal wire to be applied to the workpiece) to ensure a stable melting and/or burnout point of the consumable electrode or metal wire. can be selected to match the amount of metal droplets). Thus, deposition of molten metal without overheating the substrate and, at the same time, without the risk of splashing or the formation of excess molten pools, thereby losing control of the compaction of the deposited material. It is possible to increase the speed.

Systems for producing near net shape metal objects using additive manufacturing provided herein overcome the problems associated with metal grain columnar structure and large grain size found in many conventional additive manufacturing products. A jet device is utilized which greatly relieves. Jet devices for delivery of cooling gas jets to or near the molten pool, or jet devices for delivery of cooling gas jets to the solidifying metal, or to or to the vicinity of the molten pool A product manufactured using a system provided herein including a first jetting device for delivery of a cooling gas jet and a second jetting device for delivery of a cooling gas jet to a solidifying metal. The grain structure of results in a manufactured metal product having metal grains that are substantially equiaxed and exhibit a refined structure. One or more jetting devices provided herein are used to apply cooling gas during additive manufacturing to the free surface of the weld pool or to points across the weld pool or as the molten metal cools. By causing a gas jet to impinge on the liquid-solid boundary at the time, or on the solidifying metal beyond the liquid-solid boundary, or any combination thereof, resulting in finely divided crystals. Manufactured products with a grain structure result, and products produced using these systems exhibit improved strength, fatigue resistance, and durability.

A jetting device that directs jets of inert gas at the liquid-solid boundary of the weld pool can induce or accelerate opposing solidification fronts at the weld pool free surface. Epitaxy inhibition can be achieved when a continuous layer nucleates and solidifies from the grains of the top layer. Forced cooling by concentrated turbulence in jet devices directed at regions of the material in the solidified state, which may affect the final crystal structure and local ordering, solid phase transformations, precipitation Reactions and other second order phase phenomena can be controlled or modulated.

In situ directing a turbulent flow of cooling gas onto the solidified material of the deposited layer 480 to increase the cooling rate by applying the jet of cooling gas in situ to the deposited solidified material. A depiction of an exemplary system including the apparatus is depicted in FIG. The depicted system heats and melts the metal wire 350 from the wire feeder 300 to form droplets of molten metal 375 that fall on the workpiece 400 and form a molten pool 425 on the workpiece 400. It includes a single melting tool 200 which is the primary melting tool that produces the primary PTA arc 330, which is the primary melting tool. Forced cooling of the as-deposited material during the deposition process by jets of cooling gas 530 provided by the jetting device 500 can achieve microstructural refinement of the additive manufactured product.

As shown in FIG. 7, the system includes a jet device 500 connected to a wire feeder 300 and a separate wire feeder 500 directly (as depicted for the temperature sensor 550 embodiment) or bracket 570. can include temperature sensors 550 and 560 attached via (as in the depiction of the embodiment of temperature sensor 560). Although the embodiment of the system depicted in FIG. 7 shows temperature sensor 550 and temperature sensor 560 connected to wire feeder 300, such mounting is merely exemplary.

A system that allows application of a cooling gas to a desired surface of a workpiece and appropriate temperature measurement of the workpiece where the cooling gas jet is directed in situ, for example as illustrated in FIGS. Separate brackets or mounting arms may be used to separately and individually mount each of the cooling jet device 500 and the temperature sensors 550 and 560 to one or more components of the . In some configurations, the temperature sensor 550 can be attached to the melting tool 200 directly or via a bracket 575, as illustrated in FIG. In other configurations, a temperature sensor 550 can be attached to the bracket 250, as illustrated in FIG. Bracket 250 may attach to or hold wire feeder 300, or may attach to or hold melting tool 200, or may be one of the system or attached to other components, or holding one or more other components of the system, or any combination thereof.

Similarly, in some configurations, temperature sensor 560 can be attached to wire feeder 300 directly or through bracket 570, or attached to a bracket that can be the same as or different from bracket 250. However, such a bracket 250 can attach to or hold one or more components of the system. For illustrative purposes, FIG. 8 shows temperature sensor 560 connected to bracket 250 like temperature sensor 550, which, as previously described, is connected to wire feeder 300, one of the systems. or multiple components, or combinations thereof, or may hold wire feeder 300, one or more components of the system, or combinations thereof.

In some configurations, the temperature sensor allows the bulk of the temperature sensor to be attached to another component of the system at a location remote from the infrared fiber optic sensor or detector, while the cooling gas jet 530 is An infrared fiber optic sensor or detector can be included to allow non-contact measurement of the surface of the oriented deposited layer 480 . Temperature sensor 550 is positioned to allow temperature readings to be taken on the workpiece surface in front of the zone of application of the jet of cooling gas. A temperature sensor 560 is positioned to allow temperature readings to be taken on the workpiece surface behind the application zone of the jet of cooling gas. The positioning of the temperature sensor and jet device can depend on which temperature regions of the workpiece are most important to capture and affect the cooling rate. Positioning can be adjusted based on the metal alloy to be deposited.

FIG. 8 shows a first jetting device for directing a turbulent flow of cooling gas onto the liquid-solid boundary of the weld pool and forced cooling by directing a turbulent flow of cooling gas onto the solidified material of the deposited layer 480 . An exemplary system is depicted that includes a second jet device that provides a . The depicted system heats and melts the metal wire 350 from the wire feeder 300 to form droplets of molten metal 375 that fall on the workpiece 400 and form a molten pool 425 on the workpiece 400. It includes a single melting tool 200 which is the primary melting tool that produces the primary PTA arc 330, which is the primary melting tool. Without the application of cooling gas by the cooling jet device 100 , columnar structures typical of additive manufacturing processes can occur as solidified crystals 435 in the deposited layer 480 . For example, in the Ti-6Al-4V alloy, the spatial and crystalline solidification of the first region or solidification zone 430 is directional and dictated by a steep thermal gradient from the heat source/melt pool to the workpiece. epitaxial to the β grains. As cooling continues, crystals may solidify in a second zone containing solidified material 450, followed by a transition in which the crystallinity and morphology of the α-β microstructure changes during the allotropic transformation. These are pre-existing β-grain structure effects due to orientational relationships, grain boundary nucleation and alignment due to interfacial energies, diffusion rates and thermal conductivity differences between different crystallographic directions in the lattice. receive directly.

In the system depicted, a cooling gas jet 30 from the nozzle 25 of the jet device 100 is directed at the liquid-solid boundary of the weld pool. The impingement of the gas jets 30 at the liquid-solid boundary of the molten pool 425 induces and accelerates opposing solidification fronts 440 at the molten pool surface. Epitaxy inhibition is achieved when a continuous layer nucleates and solidifies from the grains of the top layer. The forced cooling caused by the gas jet 30 of the jet device 100 is a concentrated turbulent flow applied by the jet device across the molten pool, at the surface of the molten pool, at the liquid-solid boundary of the molten pool, or a combination thereof. strengthened by

Forced cooling by focused turbulence is provided by or depicted by extensions of the cooling jet apparatus 100 to control solid phase transitions, such as β-α solid phase transformations in titanium alloys, or precipitation reactions in nickel-based superalloys. applied to the solidified state material of the deposited layer 480 to control the solid phase transformation by means of a second jetting device 500 for directing a cooling gas jet 525 into the solidified state material in the zone 450 as described above. can do.

As shown, the system includes a second jet device 500 and at least two temperature sensors for monitoring temperature throughout the additive manufacturing process. In the depicted embodiment, a first temperature sensor 550 attached to the bracket 250 monitors the temperature at the surface of the as-deposited material prior to application of the cooling gas, such as at the solidification region 440. be able to. A second temperature sensor 560 located behind the jet device may be included to measure the temperature of the workpiece surface 565 after application of the cooling gas to the string of workpieces by the second jet device. Temperature monitoring through the use of temperature data from the first and second temperature sensors, for example, the flow rate of cooling gas applied using the second jetting device 500 or the sustained flow of cooling gas toward the workpiece Adjusting the time, or both, can allow the user to control the cooling rate. If two separate cooling jet devices are used, a single cooling gas supply can be used to provide cooling gas to each jet device. Alternatively, each cooling jet device can be attached to a separate cooling gas supply.

Although an exemplary system using one torch system is shown, the method is not limited to such a system. A two torch system can also be used.

An exemplary two torch system is shown in FIG. In the system depicted, the melting tool 600 forms a preheat zone 415 that preheats the workpiece 400 making the workpiece 400 more receptive to molten metal. The secondary melting tool 200 , the primary melting tool that produces the primary PTA arc 330 , heats and melts the metal wire 350 from the wire feeder 300 , dropping the molten metal to form a molten pool 425 . A drop 375 is formed. Without the application of cooling gas by the spouting device 100 , columnar structures typical of additive manufacturing processes can occur as solidified crystals 435 in the deposited layer 480 . For example, in the Ti-6Al-4V alloy, the spatial and crystalline solidification of the first region or solidification zone 430 is directional and dictated by a steep thermal gradient from the heat source/pool to the workpiece. epitaxial to the β grains. As cooling continues, the crystals solidify in the second zone 450 to form solidified material.

In the depicted system, the cooling gas jet 30 from the nozzle 25 of the jet device 100 is directed at the liquid-solid boundary of the weld pool. The impingement of the gas jet 30 on the liquid-solid boundary of the weld pool 425 induces and promotes opposing solidification fronts 440 at the surface of the weld pool. Epitaxy inhibition is achieved when a continuous layer nucleates and solidifies from the grains of the top layer. The forced cooling caused by the gas jet 30 of the jet device 100 is concentrated by the jet device applied across the molten pool, at the surface of the molten pool, at the liquid-solid boundary of the molten pool, or any combination thereof. enhanced by turbulence.

Forced cooling by concentrated turbulence applies cooling gas to the material in the solidified state in zone 450 to control solid phase transitions, such as the β-α solid phase transformation in titanium alloys, or precipitation reactions in nickel-based superalloys. A second jet device 500 for directing the jet 525 can be applied to the material in the solidified state to control the solid phase transformation.

As shown, the system includes a second jet device 500 and at least two temperature sensors for monitoring temperature throughout the additive manufacturing process. In the depicted embodiment, the first temperature sensor 550 can monitor the temperature at the surface of the as-deposited material prior to application of the cooling gas, such as at a post-solidification temperature monitoring region 555. can. A second temperature sensor, located behind the jetting device, measures the temperature of the workpiece surface 565 after application of the cooling gas to the string of workpieces by the second jetting device 500, such as in the post-transformation temperature monitoring region 565. can be included to measure Temperature monitoring through the use of temperature data from the first and second temperature sensors, for example, the flow rate of cooling gas applied using the second jetting device 500 or the sustained flow of cooling gas toward the workpiece Adjusting the time, or both, can allow the user to control the cooling rate.

D. Method A method for producing a three-dimensional object of metallic material by additive manufacturing, wherein the object is made by fusing together successive deposits of metallic material onto a base material, the method comprising: using, for example, to preheat at least a portion of the surface of the base material at locations where the metallic material is to be deposited, and using a second heating device to deposit molten metallic material onto the preheated areas of the base material. Heating and melting a metallic material and using the spouting device provided herein, to directing the cooling gas to impinge on the solidifying material adjacent to the , or any combination thereof, and so that the continuous deposit of molten metallic material solidifies to form a three-dimensional object; A method is also provided comprising moving the preform in a predetermined pattern with respect to the position of the heating device and the second heating device and the jet device.

In one method, the jetting apparatus provided herein directs a cooling gas with turbulence across the weld pool, at the surface of the weld pool, at the liquid-solid boundary of the weld pool, or any combination thereof. Orient. In another method, the jetting apparatus provided herein provides a cooling gas flow with turbulence into the material in the solidified state in a solid state transformation zone, such as an allotropic transformation region, or a region where precipitation reactions can occur. orient the In another method, the first jetting device provided herein has turbulence across the molten pool, at the surface of the molten pool, at the liquid-solid boundary of the molten pool, or any combination thereof. A second jetting device that directs the cooling gas and is provided herein directs the cooling gas with turbulence at the material in the solidified state, such as in the solid phase transformation zone.

In the methods provided herein, the cooling gas can include inert gases such as argon, helium, neon, xenon, krypton, and combinations thereof. The cooling gas can be a non-inert gas. The cooling gas can be a mixture of different elemental gases. The cooling gas directed across the weld pool, to the surface of the weld pool, to the liquid-solid boundary of the weld pool, or any combination thereof can have a flow rate of from about 1 L/min to about 2001 L/min. . Cooling gas directed at the material in the solidified state can have a flow rate of about 0.01 L/min to about 300 L/min. The cooling gas can be applied in a steady flow, can be applied intermittently, or can be applied in a pulsatile flow.

The temperature of the cooling gas applied can be any temperature. The cooling gas temperature can be the ambient temperature of the additive forming process. Typically, the cooling gas temperature can be about room temperature or lower, such as about 25° C. or lower. The temperature of the gas can be any temperature that cools the surfaces with which the gas interacts. The temperature can be less than 100°C, or less than 50°C, or less than 30°C, or less than 25°C, or less than 10°C, or less than 5°C, or less than 0°C. Cryogenic gases can also be used. For example, the temperature of the cooling gas delivered to the inlet of the jet device can be from -195°C to 25°C, or from about -195°C to about 25°C.

The method provided herein uses a jet device with at least two temperature sensors to measure and generate a target cooling rate. The positioning of the temperature sensor and jetting device can depend on the temperature region considered important to capture and affect the cooling rate. Positioning can be adjusted based on the metal alloy to be deposited. The temperature sensor can include an IR thermometer to capture the surface temperature of the deposited string material of the workpiece before and after application of the turbulent jet of cooling gas. Based on the data, the cooling gas flow rate and/or duration can be adjusted to increase or decrease the cooling rate. In some methods, temperature data is captured and used to provide in-process feedback control to allow partial or full automation of cooling rates used in additive manufacturing processes. Also, the data can be captured and used to design a post-process iterative deposit development program/schedule to automate the deposition of workpieces.

The desired cooling rate can be alloy dependent. Different alloys can exhibit different changes in solid phase transformation depending on the temperature range and the time of exposure to a particular temperature range. For example, for many titanium alloys, the methods provided herein have target cooling temperatures in the range of 1200° C. to about 600° C., or 1050° C. to about 800° C. to promote allotropic transformation. For steel alloys, the target cooling temperature can be in the range of 1000° C. to about 300° C., or about 800° C. to 400° C. to promote the desired solid phase transformation. For example, for the Ti-6Al-4V alloy, the cooling effect by a gas jet device directed at the material in the solidified state in this temperature range typically results in a beneficial finesse from what results in undesirable colony/lamellar structures. It can be used to increase the cooling rate to a condition that promotes basket weave structure. This cooling effect corresponds to increasing the bulk cooling rate in the phase transformation region to about 10° C./s to 15° C./s for each temperature measurement during the test. Due to localized gas jet impingement, the temperature captured on the workpiece surface in such cases was 80-140° C./s. A relationship between the measured surface cooling rate and the observed bulk cooling rate needs to be established for the alloy of interest. At the top of the deposition string, the cooling rate increases, but this top is reheated to a temperature above the transformation temperature during successive depositions, so that what remains in the finished deposit is the heat of each layer. Only segments on the bottom side of the zone of influence. A steel with a critical temperature range for transformation during cooling, typically 800-400°C.

In the methods provided herein, suitable localized cooling for a period of time determined by temperature readings from a temperature sensor measuring the surface temperature of the deposition string is required to form a joint or transition in the workpiece. can be used to dissipate the input local higher energy, which can be The method allows continuous control of the cooling rate during material addition and can be used to provide local preconditioning between string depositions. The methods provided herein allow the cooling gas flow rate to be adjusted based on changes in the thermal conditions of the workpiece being processed. The turbulent cooling gas flow can be increased as residual heat builds up during additive manufacturing or to dissipate the heat added to form certain structures, such as joints and transitions. can.

In the methods provided herein, turbulent flow from the jet device nozzles can typically be achieved due to the high velocity of the cooling gas through the nozzles. Other techniques can also be used to create turbulence in the cooling gas. For example, some of the nozzles of the jet device may be positioned such that jets of cooling gas from at least two nozzles impinge on each other to create a turbulent flow of cooling gas in the vicinity of the weld pool. The nozzle may include protrusions or depressions or a combination thereof in the nozzle orifice or in the nozzle body to disrupt laminar flow and promote turbulent flow. Typically, the velocity of the cooling gas flowing through the nozzle is selected so that the gas exiting the nozzle exhibits turbulent rather than laminar flow.

The number of nozzles and the configuration of the nozzles provide cooling gas to cover a target length of the workpiece along the direction of travel, e.g. You can choose to send it.

Typical process conditions conventionally used in additive manufacturing usually result in directional solidification and columnar grain growth due to the presence of steep thermal gradients, but this is dependent on the alloy utilized. there is a possibility. For example, for the Ti-6Al-4V alloy, spatial and crystallographic β crystals where solidification is directional and dictated by process characteristics including steep thermal gradients from the heat source/melt pool to the workpiece It is epitaxial to the grain. The crystallinity and morphology of the α-β microstructure of the Ti-6Al-4V alloy during the allotropic transformation are attributed to differences in interfacial energy, diffusion rate and thermal conductivity between different crystallographic directions in the lattice orientation. The relationship, nucleation and alignment of grain boundaries directly influences the β-grain structure that preceded it. This macro-micro interaction leads to the long-range restriction of the crystallographic and morphological diversity within the β grains that occurred earlier, and thus to significant differences in the strain response at the β grain boundaries.

The methods provided herein allow reduction of the weld pool length. Reducing the weld pool length can be achieved by increasing the solidification rate at the trailing edge of the weld pool. Application of turbulent cooling gas to the weld pool increases solidification and reduces the time in which solidification occurs. Depending on the solidification rate achieved by applying the cooling gas using the jet apparatus provided herein, the overall weld pool length can be reduced by about 10% to about 50%. For example, compared to conventional additive manufacturing methods and systems, the weld pool length is 90% or less, or 80% or less, or 70% or less, or 60% or less than the weld pool length in conventional additive manufacturing techniques. , or 50% or less.

The spouting device provided herein promotes grain refinement. Controlling process parameters can assist in its effectiveness. This is especially true in alloys such as Ti-6Al-4V, which are resistant to solidification refinement due to the narrow solidification temperature range exhibited by the alloys. The solidification properties make structural supercooling unlikely at the thermal gradients and solidification rates typical of metal additive manufacturing.

The jet apparatus provided herein can be used in metal additive manufacturing configurations using a single melting apparatus or a single torch configuration. The jetting device provided herein can be used in two torch configurations for metal additive manufacturing. A preheat torch can be used to achieve workpiece surface temperature control for specific purposes. A separate second torch can be used as a melting torch for melting feedstock, such as metal wire. The thermal gradient can be adjusted by suppressing the energy intensity required of the melting torch and controlling the desired level of molten metal by ensuring wettability at the periphery of the molten pool without overheating the pool itself. can be adjusted to achieve a contact angle of Adjustment of the thermal gradient is beneficial for grain refinement, but is not necessary to achieve the effect achieved by using a jetting device.

The purposeful transfer of energy to the wire, which also involves resistive heating of the wire, allows a high degree of energy efficiency without transferring excessive energy directly to the weld pool as would be the case if the energy source that melts the wire is also transferred to the weld pool. Allows deposition rate. Such an arrangement can reduce overheating of the weld pool and thus reduce thermal gradients. Such an arrangement also allows sufficient deposition rate to maintain an extended weld pool length and allows interaction of the gas jets from the jet device on or near the weld pool surface. Reducing these thermal gradients can be beneficial for grain refinement, but it is not sufficient to achieve the grain refinement effect achieved by the application of cooling gas using the spouting device provided herein. Not necessary.

Additional aspects of weld pool control and string shape control are apparent from testing of the jet device test. As noted above, the methods provided herein enable reduction of the weld pool length, which is achieved by increasing the solidification rate at the trailing edge of the weld pool. can be done. The method provides the ability to shape the string to a wider single row wall and eliminate the need for filling at the ends of the string by melt displacement due to gas jet pressure towards the ends. The methods provided herein enable refinement of the solidified structure of workpieces produced by additive manufacturing processes. The method can eliminate or significantly reduce the rough columnar structures typically produced by conventional additive manufacturing systems. Elimination of these rough columnar structures can result in manufactured products that exhibit higher strength, ductility and fatigue resistance than is achievable with conventional additive manufacturing processes.

Electron Backscatter Diffraction (EBSD) is an analysis of crystal structure including determination of grain size and grain boundary type, orientation difference, deformation, phase discrimination and distribution, crystallographic orientation and texture (crystallographic micro and macro texture) enable For deposited layers, EBSD can be used to inspect epitaxy and crystallographic orientation between layers. The elongated columnar structure typical of conventional additive manufacturing processes imposes a limit on the number of desirable alpha grain variations that can occur in Ti-6Al-4V samples. This contrasts with that achieved using the method provided herein (FIG. 4B), where gas jet impingement results in a material with finer grains. 4A and 4B, which show the crystallographic EBSD characterization of a typical material (FIG. 4A) made by As can be seen in FIG. 4A, the typical coarse-grained material from conventional processes exhibits long-range alignment and uniformity of the lamellar structure along the pre-formed β grain boundaries. Materials produced using the spout apparatus and methods provided herein have increased crystallographic diversity, with the materials exhibiting a large number of initial β grain orientations. As can be seen in FIG. 4B, the grain-refined material produced using the spout apparatus and methods provided herein has reduced grain boundary alignment.

A method of minimizing or eliminating coarse columnar solidification structures in additively manufactured metal products is also provided. The method includes applying a turbulent cooling gas jet to the free surface of the weld pool using a jetting device provided herein. Cooling gas jets directed to the weld pool, such as the liquid-solid boundary of the weld pool, induce and/or accelerate the growth of opposing solidification fronts at the weld pool free surface. This prevents epitaxy as successive layers nucleate and solidify from the grains of the topmost layer, thereby minimizing or eliminating the formation of coarse columnar solidification structures. Nucleation at the weld pool free surface can result in fracture of the columnar solidification structure with irregularly spaced finer particles, which imparts enhanced and reproducible material properties. May be achieved during the manufacturing process. The method can result in increased crystallographic diversity, such as the formation of a large number of initial β grain orientations. The method can also reduce grain boundary alignment. The method can also result in reduced strain shear in additively manufactured metal products. The method is especially useful when loaded parallel to the build direction for typical materials not produced using the methods provided herein, including gas jet impingement using jet devices such as those described. A final material can be produced that exhibits enhanced curability. Additively manufactured products produced using this method may also exhibit improved ductility in the production direction (along the string).

A method of refining the microstructure of an additive manufacturing metal product is also provided. The method includes increasing the cooling rate by in situ applying a jet of cooling gas to the material in its deposited and solidified state using the cooling jet apparatus provided herein. Forced cooling of the as-deposited material during the deposition process can achieve microstructural refinement of the additive manufacturing product. The cooling rate can greatly affect the microstructures formed during the manufacturing process. In some methods, the allotropic transformation can be tuned or controlled by in situ application of a turbulent cooling gas to the deposited material in its solidified state. In methods where the deposited material is a titanium alloy such as Ti-6Al-4V, β-α solidification is achieved by forced cooling by in situ application of a turbulent cooling gas to the deposited material in the solidified state. Phase transformation can be controlled. The methods of grain refinement provided herein provide long-range strain resistance at boundaries due to microstructural duality by obtaining different microstructural elements that exist in a more homogeneous and finely dispersed state. Alignment can be addressed.

10A and 10B, the effect of cooling rate on the microstructure can be seen. A high deposition rate additive manufacturing process based on plasma and wire utilizing Ti-6Al-4V alloy was used to form the product. It has been found that cooling at a higher cooling rate significantly refines the microstructure of the deposited product. When the temperature of the deposited material drops from 1000° C. to 900° C. at the measured bulk cooling rate of 15° C./s than when cooled at the measured bulk cooling rate of 15° C./s (FIG. 10A). (FIG. 10B), an even finer basketweave microstructure was achieved. The hard recesses (dark pyramid-shaped depressions in the middle of the figure), when tested for hardness, showed a refined basket weave microstructure (FIG. 10B) compared to a less refined basket weave microstructure (FIG. 10). The figure shows that the uniformity of the plastic deformation of is improved. As can be seen in FIG. 10A, there is a localized concentration of plastic deformation near the recess. FIG. 10B does not show local concentrations of plastic deformation. Therefore, allotropic phase transformations (transformation from one crystal structure to another), precipitation, and other solid state transformations can be achieved by applying cooling gas jets to forcefully cool the material in the as-deposited state during deposition. A finer basket weave microstructure can be achieved as well as improved phase thermochemical reactions.

A method is also provided for in-situ forced cooling of additively manufactured metal objects. The method includes in-situ applying a jet of cooling gas to the deposited and solidified material to increase the cooling rate of the material. The cooling gas jet is applied in turbulence by a jet device and has a bulk cooling rate of about 10° C./s to about 25° C./s, or about 80° C./s to 150° C. measured at the surface to which the cooling gas is directed. A recorded cooling rate of °C/sec can be achieved.

Also provided is a method for enhancing the uniformity of plastic deformation of additively manufactured titanium alloys, such as in situ Ti-6Al-4V metal objects. The method increases the cooling rate of the material in its deposited and solidified state, thereby promoting the formation of a finer basket weave microstructure rather than the typically produced colony/lamellar microstructure. It involves applying a jet of cooling gas in situ to the material. Cooling gas jets are applied in turbulence by means of a jetting device. A finer basketweave microstructure can be achieved as the cooling rate is increased, and a finer basketweave microstructure enhances the uniformity of plastic deformation. For example, increasing the bulk cooling rate to about 10° C./s to about 15° C./s when cooling an object to 1000° C. to 900° C. results in a finer basket weave microstructure and uniformity of plastic deformation. can enhance sexuality.

The methods provided herein can be performed in any additive manufacturing system. The method can be performed in a system that includes a closed chamber filled with an inert gas to provide an inert atmosphere in which the entire process is performed. The inert atmosphere can be or contain argon, xenon, neon, krypton, helium, or combinations thereof, allowing deposition in an inert atmosphere.

E. Examples The following examples are included for illustrative purposes only and are not intended to limit the scope of the embodiments provided herein.

Example 1
Plasma and Wire-Based High Deposition Rate Additive Manufacturing Utilizing Ti-6Al-4V Alloys with (A) Without and (B) Jetting Apparatus Provided Herein Injecting Cooling Gas During Additive Manufacturing used the process. The cooling gas used was room temperature argon gas. The cooling gas flow rate applied using a jet device of the type illustrated in FIG. 1 was 20 L/min. The deposition rate was 5 kg/h and the workpiece surface temperature/interpass temperature was 650°C. The deposition rate and temperature were the same whether or not a jet device was used to apply the cooling gas.

Micrographs of the results are shown in FIGS. 5A and 5B. FIG. 5A shows the structure of a metal object produced by typical additive manufacturing. The grain structure of the manufactured product in FIG. 5A is coarse and columnar structures are visible. FIG. 5B illustrates the beneficial results achieved when applying cooling gas to the weld pool using a jet device during additive manufacturing as described herein. The grain structure of the manufactured product in FIG. 5B exhibits a nearly equiaxed and refined structure. Thus, by applying cooling gas using the spouting device provided herein during additive manufacturing, the product has a refined grain structure. Manufactured products with these refined grain structures exhibit improved strength, fatigue resistance, and durability.

Example 2
Plasma utilizing Ti-6Al-4V alloy by one-sided application of cooling gas to one side of the weld pool in a single row Ti-6Al-4V string deposit using the spout apparatus provided herein and wire-based high deposition rate additive manufacturing processes were used. The cooling gas used was room temperature argon gas. The cooling gas flow rate applied using a jet device of the type illustrated in FIG. 1 was 25 L/min. The deposition rate was 5 kg/h and the temperature between deposition passes was 500°C. Argon cooling gas was applied to half of the weld pool and the other half was untreated. This was accomplished by fitting the nozzle of the jet device to only one side of the melting tool.

Results are shown in FIG. As can be seen, the untreated side (right part of the figure) exhibited a coarse grain structure and a columnar structure. The grain structure of the processed side (left side) of the manufactured product of FIG. 6 has metal grains that are substantially equiaxed and have a refined structure. The dotted line in the figure roughly indicates the typical grain size and shape of one side of the product. The grain size on the treated side is significantly smaller than that achieved with conventional additive manufacturing methods (maximum grain size <2 mm and average grain size <1 mm ² ), as shown on the right. The untreated side (left) shows a slight tilting of the columnar structure due to the effect of the impinging cooling gas on the thermal gradient. The micrographs also illustrate that the spouting devices provided herein can be used in additive manufacturing to enable the production of graded microstructures and the tuning of local material properties through manipulation of the nozzles of the spouting device. ing.

It will be apparent to those skilled in the art that various modifications and variations can be made in this invention without departing from the spirit or scope of this invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

The following is a list of reference numbers used in the specification and accompanying drawings.
10 first conduit 15 first conduit inlet 20 diffuser 25 nozzle 30 gas jet 40 cooling gas supply 50 cooling gas supply 60 second conduit 65 second conduit inlet 70 diffuser 75 nozzle 80 gas jet 85 cross member 90 molten pool 95 deposition string 100 jet device 200 melting tool 250 bracket 300 wire feeder 330 melting arc or beam 350 metal wire 375 molten metal droplet 400 workpiece 415 preheat zone 425 molten pool 430 solidification zone 435 solidified crystal 440 cooling gas jet Collision Induced Opposing Solidification 450 Solidification Material Zone 480 Sedimentary Layer 500 Second Jet Device 525 Nozzle 530 Cooling Gas Jet 550 Temperature Sensor 555 Post Solidification Temperature Monitoring Region 560 Temperature Sensor 565 Post Transformation Temperature Monitoring Region 570 Bracket 575 Bracket 600 Melting tool 630 Melting arc or beam D Direction of travel

Claims (23)

A jet apparatus for use in a metal additive manufacturing system comprising a melting tool that generates a thermal energy source to deposit molten material and form a molten pool, comprising:
The jet device is
a first conduit comprising a first inlet for receiving cooling gas and a first opening connected to a nozzle for discharging cooling gas;
a second conduit comprising a second inlet for receiving cooling gas and a second opening connected to a second nozzle for discharging cooling gas;
The first conduit is configured to attach to the melting tool on one side of the thermal energy source and the second conduit is configured to attach to the melting tool on a second side opposite the thermal energy source. configured to attach to
At least one of the first nozzles or the second nozzles is adapted to turbulence the cooling gas as it exits the at least one first conduit or the second conduit during material deposition. and wherein said first nozzle and said second nozzle direct said cooling gas into a molten pool, into solidifying material adjacent a liquid-solid boundary of said molten pool, and into said Oriented to collide with the liquid-solid boundary,
configured to prevent blowing cooling gas toward the thermal energy source;
jet device. 2. The jet device of claim 1, wherein each of said first conduit and said second conduit comprises a nozzle having separately controlled cooling gas flow. 3. A jet device according to claim 1 or 2 , made of or comprising a heat resistant material. The heat resistant material is titanium, titanium alloys, tungsten, tungsten alloys and alloys thereof, stainless steel, alloys containing chromium and nickel, nickel, iron, cobalt, copper, molybdenum, tantalum, tungsten and titanium 4. The jet device of claim 3 , selected from among alloys comprising two or more of 3. The jet device according to claim 1 , further comprising a flow meter for measuring the flow of said cooling gas. 3. A jet device according to claim 1 or 2 , wherein at least one nozzle is positioned at the tip of each conduit. 3. A jet device according to claim 1 or 2 , wherein each nozzle is positioned at an angle of 90[deg.] or less with respect to each conduit. Any one or more of the conduits
a plurality of nozzles;
a plurality of channels, pipes, tubes or lines within said conduit, each of said channels, pipes, tubes or lines being separately attached to a single nozzle of said plurality of nozzles; 3. A jet device according to claim 1 or 2 , comprising a channel, pipe, tube or line of . 3. A jet device according to claim 1 or 2 , wherein each nozzle has a cylindrical shape. each nozzle has a cross-sectional shape selected from circular, oval, oval, square, rectangular, diamond, star, pentagonal, hexagonal, and octagonal; or said nozzle has an asymmetrical cross-sectional shape. , The jet device according to claim 1 or 2 . 3. The jet device of claim 1 or 2 , wherein each nozzle has a length selected from about 5 mm to about 50 mm. A jet device according to claim 1 or 2 , wherein each nozzle has a wall thickness of about 0.1 mm to about 5 mm. 3. A jet apparatus as claimed in any one of claims 1 or 2 , wherein each nozzle comprises an orifice through which the cooling gas flows. said orifice has a cross-sectional shape that is the same as or different from said cross-sectional shape of said nozzle; 14. The jet device of claim 13 , selected among shapes. 15. A jet device according to claim 13 or 14 , wherein the orifice has a diameter equal to or smaller than the inner diameter of the nozzle. A jet device according to any one of claims 13 to 15 , wherein said orifice has a diameter of about 1 mm to about 5 mm. 3. A jet device according to claim 1 or 2 , wherein each conduit comprises a baffle that interacts with cooling gas flowing through the conduit. (a) each conduit includes protrusions or depressions or a combination thereof in the flow path of said cooling gas flowing through said conduits so as to impede laminar flow of said cooling gas and promote turbulent flow of said cooling gas; or (b) each nozzle has a protrusion or dimple in the flow path of said cooling gas flowing through said nozzle such that it impedes laminar flow of said cooling gas and promotes turbulent flow of said cooling gas. or (c) a flow of said cooling gas through said orifices such that said orifices of each nozzle impede laminar flow of said cooling gas and promote turbulent flow of said cooling gas. further comprising protrusions or depressions within the channel or a combination thereof; or (d) any combination of (a), (b) and (c).
The jet device according to claim 1 or 2 . to insulate the jet device from a melting tool, or between the jet device and a weld pool in a workpiece, or to insulate the jet device from a wire feeder,
3. The jet device according to claim 1 or 2 , further comprising a heat insulating material. A jet device according to any one of the preceding claims, further comprising a cooling gas supply. 21. The jet device of claim 20 , wherein each conduit is connected to its own supply of cooling gas. 22. A jet apparatus according to claim 20 or 21 , wherein the cooling gas supply comprises a manually or automatically adjustable regulator to regulate the flow rate of cooling gas provided to the conduit. A method for minimizing or eliminating coarse columnar solidification structures in additively manufactured metal products, comprising:
2. Using the jet apparatus of claim 1, during deposition of molten material, turbulent cooling gas jets are directed into the molten pool, into the solidified material adjacent to the liquid-solid boundary of the molten pool, and into said molten pool. comprising impingingly applying to a liquid-solid boundary;
The method, wherein the cooling gas jet induces and/or accelerates the growth of opposing solidification fronts at the surface of the molten pool.

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