DE102022100173A1 - Device and method for additive manufacturing - Google Patents

Abstract

The disclosure relates to a device for additive manufacturing, in particular by means of laser deposition welding, with a powder feed (40) for a powdered building material, the powder feed (40) generating a powder flow (42) in the direction of a substrate (14, 64) to be coated , a first radiation source (82) for generating high-energy radiation, in particular a first laser source, and a second radiation source (120) for generating high-energy radiation, in particular a second laser source, the first radiation source (82) and the second radiation source (120) are offset from one another in such a way that the supplied powdered building material first enters a beam generated by the first radiation source (82) and then enters a melt pool (50) generated essentially by the second radiation source (120) on the substrate (14, 64). . Furthermore, the disclosure relates to a method for additive manufacturing, in particular by means of laser deposition welding.

Description

The present disclosure relates to a device and a method for additive manufacturing (AM—Additive Manufacturing), in particular by means of laser deposition welding. At least in exemplary configurations, the present disclosure relates to devices and methods for coating components. Coating is also referred to as cladding. Laser cladding is used when a radiation source in the form of a laser is used.

From the DE 10 2011 100 456 B4 a method for laser deposition welding is known, which is referred to as the so-called EHLA method (so-called extreme high-speed laser deposition welding). The process uses a radiation source in the form of a focused laser beam, which applies a build material supplied in powder form to a workpiece in order to coat the workpiece. The laser beam is designed in such a way that the supplied powder is melted before it comes into contact with the workpiece. The laser beam creates a melt pool on the surface of the workpiece, to which the melted powder is fed. In this way, high application rates (e.g. area output) can be generated.

However, this process requires a high level of control technology complexity, for example when controlling the material supply and the laser beam and/or the feed control. In particular, it must be ensured that the focus of the laser beam is at a defined distance from the surface of the workpiece so that the powder can be melted there in the focus before it actually comes into contact with the workpiece. For this purpose, the focus of the powder flow above the melt pool is aligned with the laser beam by suitably positioning the powder nozzle.

The coating of components using additive processes can be used, for example, to produce an anti-corrosion layer and/or an anti-wear layer. The wear protection layer can have hardness-increasing properties.

From the DE 11 2014 006 472 T5 discloses a device for additive manufacturing by means of “direct energy deposition” (DED), in which powdered metallic building material is melted by laser radiation for the purpose of material application. The device has an optical system and a control unit that controls the optical system in such a way that the emission direction of the laser radiation is changed during the application of material. The laser beam swings or oscillates during the job.

A further increase in the performance of devices for additive manufacturing or for coating is desirable. In particular, the application in the industrial environment requires high application rates. In addition, however, materials that are as resilient as possible should be processed, in particular metal materials, ceramic materials or the like, which are supplied in powder form.

The disclosure is based on the object of specifying a method and a device for additive manufacturing, in particular for coating components, which enable a high application rate. The method and the device can preferably be precisely controlled so that a homogeneous application results overall. Further options for influencing the process can preferably be identified in order to be able to adapt parameters as required. The method and the device preferably contribute to a further reduction in overspray or to better utilization of the building material provided.

According to a first aspect, the present disclosure relates to a device for additive manufacturing, in particular by means of laser deposition welding, with a powder feed for a powdered building material, the powder feed generating a powder flow in the direction of a substrate to be coated, a first radiation source for generating a high-energy radiation, in particular a first laser source, and a second radiation source for generating high-energy radiation, in particular a second laser source, the first radiation source and the second radiation source being offset in relation to one another in such a way that the powdery building material supplied is initially divided into a beam generated by the first radiation source and thereafter enters a molten pool generated substantially by the second radiation source on the substrate.

In this way, the object on which the disclosure is based is achieved.

In other words, the focus (or the beam waist) of the first radiation source is further away from the surface of the substrate than the focus (or the beam waist) of the second radiation source. This is made possible by an offset (distance) between the foci (or beam waists) and possibly an angular offset between the optical axes of the application heads of the first radiation source and the second radiation source, at least in exemplary configurations ments. The focus is primarily defined by the respective beam guidance (optics), which is arranged in the application head.

The optical axes of the application heads of the first radiation source and the second radiation source approach each other or meet (intersect) in the immediate vicinity of the surface of the substrate in the molten bath, at least in exemplary configurations.

The foci (or focus areas) of the two radiation sources are spaced apart from one another, at least in exemplary configurations. In other words, according to exemplary configurations, the focal plane/the focal area of the first radiation source or its beam guidance is spaced further from the surface of the substrate than the focal plane/the focal area of the second radiation source or its beam guidance. In exemplary embodiments, the term focus includes both a focal plane and a focal area (for example, when there is no clear focal plane). The focus area is regularly characterized by the focal length (focus distance) and depth of focus. Within the scope of the present disclosure, the focus can also be referred to as the location of the beam waist, at least in the case of a sufficiently focused beam. The surface refers, for example, to the area of the substrate immediately before the coating, accordingly the surface is covered with the coating.

In exemplary configurations, the term additive manufacturing also includes the coating of components. Desired surface properties can be produced in this way, for example. This applies, for example, to corrosion-resistant layers, wear-resistant layers, sliding layers, thermally stable layers and the like.

In exemplary embodiments, the present disclosure is aimed at what is known as laser cladding. In other words, this involves laser coating of existing components, at least in exemplary configurations. The process can also be referred to as laser build-up welding. In exemplary embodiments, the present disclosure relates to high power laser cladding in which much of the powdered build material is melted (at least significantly heated and softened) prior to direct contact with the melt zone on the surface of the component. In this context, it is a question of processes for laser deposition welding with high deposition rates and high feed rates.

The configuration according to the disclosure with a first radiation source and a second radiation source with respective application heads allows a higher application rate or coating rate, at least in exemplary configurations. Overall, a higher process speed can be achieved, at least in exemplary configurations.

With the help of the first radiation source and the second radiation source, a sharper functional separation between the melting of the powder and the generation of the melt pool on the surface of the component to be coated (substrate) is possible. Because two radiation sources are now provided with associated application heads, which can optionally be designed and arranged individually, the sub-processes (powder melting and molten bath production) can be optimized. The sub-processes can be better controlled.

In an exemplary embodiment, the application head of the second radiation source is designed and aligned in such a way that a molten pool is generated on the surface of the substrate, the area of which is larger than the resulting area of the powder stream when it hits the substrate. In an exemplary embodiment, the resultant area of the powder flow is entirely within the cross-sectional area of the molten pool. In this way, losses (overspray - excess powder mist) in the building material can be reduced or avoided.

If only the first radiation source is used to melt the building material and to generate the melt pool on the surface of the substrate, the shading of the first radiation source by the powder ensures a significant reduction in the power impinging on the surface of the substrate. At the same time, the performance is highly dependent on the powder flow and the shadowing associated with it.

However, since, according to the disclosure, a second radiation source is additionally provided, which is aligned directly with the surface of the substrate, the generation of the molten bath can be controlled better and more precisely.

An example application is the creation of a wear protection layer on a component. The coating can take place, for example, on the circumference of a rotationally symmetrical component or over a large area on a component surface.

In exemplary configurations, at least the first radiation source or the second Radiation source designed as a laser source for generating laser radiation.

In exemplary configurations, at least the first radiation source or the second radiation source is designed as an electron beam source.

Embodiments described within the scope of this disclosure focus on radiation sources configured as lasers. It goes without saying, however, that other radiation sources can also be used, for example electron beam sources. The person skilled in the art will make any necessary structural adjustments.

The powdery building material is usually supplied via at least one nozzle. The powder is conveyed from the powder feeder to the nozzle using a transport gas. The nozzles are regularly provided, which are used both to supply the powdered building material and to supply a protective gas or process gas.

A so-called multi-jet nozzle (multi-jet nozzle) is provided by way of example, which comprises three, four, five, six, seven or more individual nozzles. The individual nozzles are distributed, for example, in a circle around the optical axis of the first laser. According to an alternative embodiment, an annular nozzle is provided, which surrounds the beam path (optical axis) of the applicator head of the first radiation source and provides supply channels for the protective gas and the powdered building material.

Depending on the specific configuration and kinematics, the device according to the disclosure is suitable for coating tubular bodies, disk bodies, flat surfaces and, if necessary, also for coating bodies with other curvatures (free-form surfaces and other geometries).

It goes without saying that, according to the disclosure, the first radiation source and the second radiation source are not “connected in parallel” in the sense of an increase in intensity, ie are coupled into one and the same beam path. The present disclosure is based on two (or more) radiation sources with a respective application head, which are intentionally arranged differently and possibly are of a different type and/or are operated differently.

The first radiation source and the second radiation source can be adapted to the respective task independently of one another. This concerns, for example, the lens, the focal length, the position and orientation of the focal plane/focal area, the resulting diameter in the focal plane/focal area, the beam waist and the like.

In this way, the first radiation source can be optimized with the associated applicator head for melting the powdered building material. The first radiation source with the associated application head can be adapted and optimized with regard to the beam geometry to the geometry of the powder flow (for example powder cone). The power of the first radiation source can also be adapted to the given conditions (type of powder, amount of powder, geometry of the powder flow and the like). The second radiation source with the associated application head can be adjusted with regard to the molten pool to be generated on the surface of the substrate. This applies, for example, to the diameter or the dimensions of the molten pool and its assignment to the impinging flow of building material (with molten powder).

The relative association between the application heads of the first radiation source and the second radiation source remains constant during processing (during an additive manufacturing process), at least in exemplary configurations. In other words, the application heads of the first radiation source and the second radiation source can use one and the same kinematics to generate a relative movement between the substrate and the two radiation sources. The relative movement can be generated by a movement of the substrate (moving table) or by a movement of an application head for the radiation source(s). It goes without saying that certain axes of movement can be provided by the workpiece (substrate) and other axes of movement by the tool (the applicator heads of the first and second radiation sources).

The device is suitable for connecting similar or different materials. In other words, the device is suitable for repair work in which similar or different materials are to be connected to one another. The device is also suitable for producing coatings, such as anti-corrosion layers or anti-wear layers.

According to an exemplary embodiment, the first radiation source and the second radiation source each have a beam guide that is arranged and configured relative to one another in such a way that the first beam guide has a focus that is spaced from a surface of the substrate, and that the second beam guide has a focus exhibiting that of the focus of the first Beam guidance is offset towards the surface of the substrate.

Within the scope of the present disclosure, the term focus also includes focus areas that do not include a clearly definable focus plane. In other words, the area in which the radiation is sufficiently focused does not necessarily have to be concentrated on one plane. The person skilled in the art is aware that in practice there is also sufficient focussing in the vicinity of such a plane to increase the energy density for build-up welding purposes.

According to a further exemplary configuration, the focus of the beam guidance of the second radiation source is adjacent to the surface of the substrate, in particular immediately adjacent. The beam guidance of the second radiation source is designed to emit the energy for generating the molten bath into the surface of the substrate.

In exemplary configurations, this ensures that the second radiation source forms a melt pool on the surface of the substrate, at least contributes to this to a greater extent than the first radiation source. This is not to be understood as limiting. In other words, the first radiation source can also make a certain contribution to the generation and/or maintenance of the melt pool.

According to a further exemplary configuration, the device is designed in such a way that the powder stream passes the focus of the beam guide of the first radiation source, with the first radiation source being designed to melt the powder stream in a focus area. The focus area is at least adjacent to the focus or a focus plane.

It goes without saying that both the first radiation source and the second radiation source ensure an energy input. Accordingly, according to exemplary configurations, the first radiation source is designed to at least essentially or at least predominantly melt the powder flow. In other words, the second radiation source can also make a certain contribution to melting the powder stream.

The first radiation source is designed and arranged in such a way that the majority of the powder stream that passes the focus of the beam guide of the first radiation source is melted by the radiation from the first radiation source. In this way, very high application rates can be achieved, comparable to that from the DE 10 2011 100 456 B4 well-known high-speed laser deposition welding.

In exemplary configurations, a large part, at least a substantial part, of the energy from the first radiation source is absorbed by the passing powder, which is melted in this way. Thus, the remaining part of the radiation energy of the first radiation source impinges on the surface of the substrate, at least in exemplary configurations. It goes without saying that the melted powder also hits the substrate and ensures an input of energy there, at least in exemplary configurations.

According to a further exemplary embodiment, the first radiation source has a head with a first optical axis and the second radiation source has a head with a second optical axis, with an angular offset between the first optical axis and the second optical axis. The heads accommodate, for example, a respective beam guide (for example beam-guiding optics) for the laser radiation generated by the first radiation source or the second radiation source.

The angular offset between the first optical axis and the second optical axis allows the desired arrangement of the respective focus to achieve the combinatorial effect. It goes without saying that the optical axes do not necessarily have to be arranged in the specific radiation source itself. The optical axes are usually defined by a beam guide in the application head, which is assigned to the respective radiation source. When using laser sources as the radiation source, a light guide is provided between the radiation source and the assigned application head, for example, with the beam guidance (for example optical beam guidance) on or in the application head defining the optical axis.

In an exemplary configuration, the first optical axis of the application head of the first radiation source is aligned at right angles (90°), at least essentially at right angles, to the surface of the substrate. An angle of 0° would be parallel to the surface of the substrate. Accordingly, the second optical axis is oriented at an angle ranging between greater than 0° and less than 90° relative to the substrate. This includes, for example, an angle between 15° and 75°, in particular an angle between 30° and 60° in relation to the surface of the substrate. A reverse assignment of the application heads of the first and second radiation source is not excluded. For a substrate with a curved surface (such as a Tubular body), this information relates to the specific section of the surface to which the first radiation source is aligned radially (at least essentially radially).

In an exemplary configuration, the optical axis of the application head of the first radiation source is aligned normal (90°) or essentially normal to the surface of the substrate. In an exemplary embodiment, the optical axis of the application head of the second radiation source is aligned normal or essentially normal to the surface of the substrate. The optical axes of the first and second radiation sources can be regularly inclined to one another. An angle of inclination of the first optical axis and/or the second optical axis is usually in a range between 45° and 90° to the surface of the substrate (i.e. in a range between 0° and 45° in relation to a normal to the surface of the substrate) . At significantly lower angles of inclination in relation to the surface, a high proportion of the energy introduced is reflected at the surface of the substrate. For example, both the first optical axis and the second optical axis are inclined relative to the normal to the surface of the substrate, for example at an angle between 0° and 45°, for example at an angle between 0° and 30°. Both application heads are aligned with their optical axes in such a way that the optical axes intersect on the surface of the substrate, or at least come close to one another.

According to a further exemplary embodiment, the first radiation source and the second radiation source can be controlled independently of one another.

In an exemplary embodiment, the radiation sources can be distinguished from one another with regard to their characteristic values. Radiation sources of different types are used by way of example, in particular with regard to the power provided and/or called up.

In an exemplary embodiment, the position and/or orientation of the two application heads of the radiation sources, in particular of their optical axes and/or foci, can be adjusted relative to one another

According to a further exemplary configuration, the alignment of the optical axis of the second radiation source can be adjusted in relation to the optical axis of the first radiation source.

In an exemplary configuration, the first radiation source or its optical axis (of the application head) is aligned at right angles (perpendicular), at least essentially at right angles (perpendicular), relative to the surface of the substrate. Accordingly, an angle of inclination of the second radiation source or the optical axis (of the application head) of the second radiation source can be adjusted in relation to the first radiation source and/or the surface of the substrate.

According to a further exemplary configuration, at least one focal distance of at least the first radiation source or the second radiation source can be adjusted in relation to the substrate. In this way, the device can be even better adapted to specific applications, component geometries and materials. Within the scope of the present disclosure, the term focus distance is to be understood as meaning a distance between the focus of the respective radiation source and the surface of the substrate, specifically along the optical axis.

In an exemplary embodiment, the beam guidance of the first radiation source and the second radiation source can be distinguished from one another with regard to their characteristic values. For example, optics of different focal lengths and focus diameters are used.

According to a further exemplary configuration, the power of at least the first radiation source or the second radiation source can be adjusted. In this way, the device can be even better adapted to specific applications, component geometries and materials.

According to a further exemplary embodiment, the first radiation source and the second radiation source are designed as lasers for generating a laser beam, with the first radiation source and the second radiation source being operated at different power levels.

In other words, the first radiation source and the second radiation source can be operated with different laser powers, for example. The term laser power refers, for example, to the energy level of the laser beam in a specific beam cross-section, for example in the focal plane. This is not to be understood as limiting.

According to a further exemplary embodiment, the first radiation source is operated with a laser power that has a ratio to the laser power of the second radiation source that is in the range from 2.0:1 to 10.0:1, in particular in the range from 4.0:1 to 9.0:1. In other words, the device can be operated in such a way that a desired relationship between the laser power of the first radiation source and the laser power of the second radiation source.

In other words, in exemplary configurations, the laser power of the first radiation source is greater than the laser power of the second radiation source. The second radiation source serves primarily to generate and maintain a melt pool on the substrate surface. The primary purpose of the first radiation source is to melt the powder particles contained in the powder stream as far as possible. In this way, a high application rate is achieved overall.

According to a further exemplary embodiment, the laser power of the first radiation source is in the range between 3.0 kW and 20 kW. This is an example of a range for the laser power in operational operation for the laser coating of components with metal materials. According to further configurations, at least partially different areas are used, for example for other materials and combinations of materials (substrate and coating).

According to a further exemplary configuration, the optical axis of the first radiation source is oriented perpendicularly or essentially perpendicularly to the substrate surface to be coated, wherein the optical axis of the second radiation source is oriented perpendicularly or essentially perpendicularly to the substrate surface to be coated. In particular, the optical axis of the second radiation source is inclined relative to the optical axis of the first radiation source, for example facing away from a coating resulting from the relative movement between the device and the substrate. In this way, an influence of the second radiation source on the bead produced immediately beforehand during the coating is avoided.

According to a further exemplary configuration, the optical axis of the first radiation source is oriented perpendicularly or essentially perpendicularly to the surface of the substrate to be coated, the optical axis of the second radiation source being inclined relative to the optical axis of the first radiation source, in particular facing away from one due to the relative movement between device and substrate resulting coating.

In other words, the optical axis of the second radiation source—seen from the optical axis of the first radiation source—is offset against the current relative movement and tilted in such a way that the beams from the two radiation sources meet in the melt pool on the surface of the substrate. This applies in particular to a feed direction of the substrate/workpiece relative to the first and second radiation source. If, on the other hand, the optical axes of the first and second radiation sources are used as a reference system, the second radiation source according to this exemplary embodiment is tilted forward (in the direction of travel) when viewed from the first radiation source, again on the side opposite the bead produced during the coating.

According to exemplary configurations, the optical axes of the application heads of the two radiation sources intersect. According to exemplary configurations, the optical axes of the application heads of the two radiation sources are arranged skewed to one another, with a minimum distance between the optical axes being provided in the immediate vicinity of the surface of the substrate.

According to a further exemplary embodiment, the powder is fed in concentrically. This is done, for example, by a nozzle in the form of an annular nozzle or multi-beam nozzle, which surrounds the beam path of the first radiation source, with the optical axis of the application head of the first radiation source being arranged in the center of the nozzle. According to a further exemplary embodiment, the powder is fed in from the side.

According to a further exemplary embodiment, the powder is introduced into an annular chamber which is formed concentrically to the center and which is open at the tip of the nozzle in the direction of the substrate. According to a further exemplary embodiment, a multi-jet nozzle with a plurality of channels for guiding the powder is provided, the channels being distributed around the optical axis and directed towards the optical axis, for example at an acute angle towards the substrate. The high-energy radiation (particularly laser radiation) emerges at the tip of the nozzle. The laser radiation and the powder flow are brought together so that a substantial part of the powder flow is melted before the powder flow contacts the surface of the substrate. The annular nozzle can be interrupted in sections, for example for reasons of stability.

It is also conceivable to design the nozzle for feeding the powder not as a ring nozzle, but as a nozzle with two, three or more channels for the powder, inclined with respect to the optical axis of the jet and aligned with the focus. In this way, the desired combination of the powder with the high-energy radiation (laser radiation) can be achieved in the focal plane or in the immediate vicinity of it.

It goes without saying that the powder can also be supplied via one or more individual nozzles which are/are aligned in a specific way relative to the optical axis of the application head of the first radiation source on the focus (focus area or focus plane) of the first radiation source.

• - Bereitstellung einer ersten Strahlungsquelle, insbesondere eines ersten Lasers,
• - Bereitstellung einer zweiten Strahlungsquelle, insbesondere eines zweiten Lasers,
• - Anordnen der ersten Strahlungsquelle und der zweiten Strahlungsquelle in einer zueinander versetzten Orientierung in Bezug auf ein Substrat,
• - Erzeugung eines Schmelzbades auf dem Substrat, insbesondere mit der zweiten Strahlungsquelle, und
• - Zuführung eines pulverförmigen Baumaterials in einen von der ersten Strahlungsquelle erzeugten Strahl, insbesondere zu einer Fokusebene der ersten Strahlungsquelle,

wobei das mittels der ersten Strahlungsquelle geschmolzene Baumaterial in das mittels der zweiten Strahlungsquelle erzeugte Schmelzbad eintritt.According to a further aspect, the present disclosure relates to a method for additive manufacturing, in particular by means of laser deposition welding, comprising the following steps:

• - Provision of a first radiation source, in particular a first laser,
• - Provision of a second radiation source, in particular a second laser,
• - arranging the first radiation source and the second radiation source in a mutually offset orientation with respect to a substrate,
• - Generation of a molten pool on the substrate, in particular with the second radiation source, and
• - Feeding a powdered building material into a beam generated by the first radiation source, in particular to a focal plane of the first radiation source,

wherein the building material melted by means of the first radiation source enters the molten pool produced by means of the second radiation source.

The object on which the disclosure is based is also achieved in this way.

It goes without saying that the method, at least in exemplary embodiments, is not necessarily designed in such a way that the powdered building material is melted exclusively by the first radiation source and that the melt pool on the substrate is generated exclusively by the second radiation source. The first radiation source can contribute at least in part to generating and maintaining the molten pool. The second radiation source can at least partially contribute to the melting of the powdered building material.

According to an exemplary configuration of the method, the first radiation source and the second radiation source are inclined relative to one another, with the first radiation source and the second radiation source being arranged in such a way that the focal plane of the first radiation source is at a distance from a surface of the substrate, and that a focal plane of the second Radiation source is offset from the focal plane of the first radiation source in the direction of the surface of the substrate.

According to a further exemplary embodiment of the method, the second radiation source is arranged and controlled in such a way that the melt pool generated on the surface of the substrate is larger than the resulting area of the powder flow when it hits the substrate. In this way, the powder flow can penetrate the molten pool in a concentrated manner, spray losses (overspray) can be significantly reduced.

It goes without saying that the method can be designed according to the disclosed configurations of the device, and vice versa. The method is suitable for using a device according to the disclosure (for example a coating system). The device according to the disclosure is suitable for use in the method according to the disclosure.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present disclosure.

• 1: eine schematische, vereinfachte Teildarstellung einer Vorrichtung zur additiven Fertigung, insbesondere zum Auftragsschweißen;
• 2: eine perspektivische Ansicht eines beispielhaften Substrats in Form eines Rohrkörpers;
• 3: eine perspektivische Ansicht eines beispielhaften Substrats in Form eines Scheibenkörpers;
• 4: eine vereinfachte schematische Ansicht einer Vorrichtung zur additiven Fertigung, insbesondere zum Auftragsschweißen, mit einer Strahlungsquelle;
• 5: eine schematische Ansicht zur Veranschaulichung eines Prozesses zur additiven Fertigung, insbesondere zum Auftragsschweißen, mit einer Strahlungsquelle;
• 6: eine vereinfachte schematische Ansicht einer Vorrichtung zur additiven Fertigung, insbesondere zum Auftragsschweißen, mit einer ersten und einer zweiten Strahlungsquelle;
• 7: eine schematische Ansicht zur Veranschaulichung eines Prozesses zur additiven Fertigung, insbesondere zum Auftragsschweißen, mit einer ersten und einer zweiten Strahlungsquelle;
• 8: eine weitere schematische Ansicht zur Veranschaulichung eines Prozesses zur additiven Fertigung mit einer ersten und einer zweiten Strahlungsquelle; und
• 9: ein Blockdiagramm zur Veranschaulichung einer beispielhaften Ausgestaltung eines Verfahrens zur additiven Fertigung.

Further features and advantages of the invention result from the following description and explanation of several exemplary embodiments with reference to the drawings. Show it:

• 1 1: a schematic, simplified partial illustration of a device for additive manufacturing, in particular for build-up welding;
• 2 1: a perspective view of an exemplary substrate in the form of a tubular body;
• 3 1: a perspective view of an exemplary substrate in the form of a disk body;
• 4 1: a simplified schematic view of a device for additive manufacturing, in particular for build-up welding, with a radiation source;
• 5 1: a schematic view to illustrate a process for additive manufacturing, in particular for build-up welding, with a radiation source;
• 6 1: a simplified schematic view of a device for additive manufacturing, in particular for build-up welding, with a first and a second radiation source;
• 7 1: a schematic view to illustrate a process for additive manufacturing, in particular for build-up welding, with a first and a second radiation source;
• 8th 1: a further schematic view to illustrate a process for additive manufacturing with a first and a second radiation source; and
• 9 : a block diagram to illustrate an exemplary embodiment of a method for additive manufacturing.

1 FIG. 12 shows, on the basis of a schematic representation, an exemplary embodiment of a device for additive manufacturing by means of build-up welding, the device being denoted overall by 10. FIG. The device 10 is supplemented with reference to FIG 4 and 5 illustrated. The 2 and 3 illustrate exemplary workpieces.

In the 1 The sectional partial view of the device 10 shown is, for example, a section of a working head/application head (compare reference number 80 in 4 ). The device 10 is used for additive manufacturing, in particular for coating a workpiece 12. In 1 and 2 a tubular workpiece 12 is shown as an example. It can be a tube, a cylinder, a piston or the like.

Workpiece 12 is also referred to as substrate 14 throughout the disclosure. The device 10 serves to produce a coating 16 on a surface 18 of the substrate 14 . The coating 16 includes, for example, metallic materials, ceramic materials and the like. The coating 16 serves, for example, as an anti-corrosion layer, a wear-protection layer, a sliding layer, a decorative layer or as a functional layer in some other way.

The device 10 has a nozzle unit 20 which comprises at least one outlet nozzle 22 . The exit nozzle 22 is aligned with the substrate 14 . During operation, the nozzle unit 20 surrounds a laser beam 26 . By way of example, the nozzle unit 20 is designed to be rotationally symmetrical about an optical axis 28 of the laser beam 26 , at least in sections. In the embodiment according to 1 the nozzle unit 20 accommodates optical elements or elements for beam guidance 30 for the laser beam 26 in its center. The beam guidance 30 comprises optical components and defines the optical axis 28. The beam guidance 30 is usually arranged on or in an application head (compare the head 80 in 4 ).

In 1 34 indicates a supply of protective gas. The protective gas supply serves to supply a process gas or protective gas 36. In the exemplary embodiment, the protective gas 36 is fed directly to the laser beam 26 in order to prevent undesirable reactions of the molten material with the surrounding atmosphere, in particular oxygen.

A powder feed 40 is also provided to provide a powder flow 42 through the nozzle unit 20 . The device 10 uses building material in powder form, which is provided via the powder feed 40 , flows through channels 44 of the nozzle unit 20 as a powder stream 42 and emerges from the outlet nozzle 22 in the direction of the surface 18 of the substrate 14 . The laser beam 26 generates a molten bath 50 there. In this way, the already partially melted or melted powdered building material can be applied to the substrate 14 in order to form a coating 16 there.

In 1 a relative movement between the substrate 14 and the nozzle unit 20 is indicated with 54 . In the exemplary embodiment, the relative movement 54 is a rotation about an axis 56 of the workpiece 12. In this way, for example, a helical bead can be produced, which forms the coating 16 along the longitudinal extension of the workpiece 12 overall. This is not to be understood as limiting.

2 shows a perspective view of the in 1 The desired coating can be produced on the substrate 14 by a suitable combination of rotation (arrow 54) about the axis 56 and feed (arrow 58) along the axis 56. The coating 16 has, for example, a structure that is similar to a thread. It goes without saying that adjacent "turns" of the helical bead are arranged so close to one another that the result is a sufficiently smooth surface. In order to vary and optimize the surface quality, the overlapping of the successive welding tracks can be changed. For example, you can work with values between 20% and 80% overlap.

3 FIG. 1 additionally shows a workpiece 62 which is designed in the form of a flange or disk. For example, the workpiece 62 is a base body of a brake disc. This is not to be understood as limiting. The workpiece 62 includes a substrate 64 on which a coating can be produced. The relative movement between the workpiece 62 and an application head of a device 10 includes, for example, a rotation 68 about an axis 66 and a radial component nominal (feed rate 70, dependent on direction). In this way, a coating with a spiral bead can be created, comparable to the groove structure of a record. Again, adjacent turns can be so close to each other that an essentially seamless surface results. In order to vary and optimize the surface quality, the overlapping of the successive welding tracks can be changed. For example, you can work with values between 20% and 80% overlap.

It goes without saying that the device 10 can also be used for coating other components with flat and/or curved surfaces.

4 shows a schematic view of in 1 Apparatus 10 shown in part. The apparatus 10 can also be referred to as a system for additive manufacturing, in particular as a system for coating by means of "direct energy deposition" (DED). The apparatus 10 includes a base 74 which supports the substrate 14 to be coated. In the exemplary embodiment, kinematics are indicated with 76, which provide the necessary axes of movement (relative movements) for producing the coating. The kinematics 76 are designed, for example, as Cartesian kinematics with mutually perpendicular axes, robot kinematics with an open or closed kinematic chain, or as a mixed form. The form of the kinematics 76 is regularly selected taking into account the workpiece to be coated.

The device 10 includes a head 80, which can also be referred to as an application head. The head 80 is coupled to a radiation source 82, for example via a light guide 84. For example, the radiation source 82 is fixed to the frame, whereas the head 80 can be moved via the kinematics 76. The radiation source 82 generates high-energy radiation. For the sake of illustration, it is assumed that the high-energy radiation is laser radiation. This should not be understood in a limiting sense. In principle, it is also conceivable to use electron beams to produce coatings.

The kinematics 76 can, for example, move the base 74 with the substrate 14 relative to the head 80 . However, it is also conceivable to move the head 18 relative to the base 74. Configurations are also conceivable in which at least one movement axis is provided for the base 74 and at least one further movement axis is provided for the head 18 .

The laser radiation 26 generated by the radiation source 82 is guided via a beam guide 30 (with optics) to a nozzle unit 20 and finally onto a surface 18 of the substrate 14 to be coated. The beam guide 30 defines the optical axis 28. In the exemplary embodiment, the optical axis 28 of the laser beam 26 is aligned essentially perpendicularly to the surface 18. As previously in connection with 1 explained, a powder feed 40 is also provided, which provides a powder flow that leaves the head 80 through the nozzle unit 20 in the direction of the surface 18 of the substrate 14 in the exemplary embodiment.

In 4 a control device is also indicated with 90, which is coupled to the head 80, the radiation source 82, the base 74 and (not shown) the kinematics 76 via control lines.

5 1 illustrates a conceivable process for producing the coating 16 on the surface 18 of the substrate 14. In this context, reference is made to that in FIG DE 10 2011 100 456 B4 procedures described.

The laser beam 26 is aligned with its optical axis 28 essentially perpendicular to the surface 18 of the substrate 14 . Furthermore, powder is provided in the form of a powder stream 42 via a powder feed. The powder stream 42 is designed as a powder cone, for example. The laser beam 26 is a high-energy laser beam. The laser beam 26 is capable of at least partially melting the powder stream 42 and the surface 18 of the substrate 14 . A melt pool 50 forms on the surface 18.

The powder flow 42 is guided to a focus 94 of the laser beam 26 . A considerable part of the powder flow 42 is already melted there. The energy of the laser beam 26 is highly concentrated in the focus 94 (location of the beam waist). This area can also be referred to as the powder melting zone 98 . The focus 94 or the powder melting zone 98 is at a distance from the surface 18 of the substrate 14 . The building material (partially melted powder stream 42) overcomes a powder path 100 between the powder melting zone 98 and the melt pool 50 with the laser beam 26. The laser beam 26 still has a residual power when it strikes the surface 18 of the substrate 14. Due to the shading by the powder contained in the powder flow 42, however, this is lower than the original power in front of the powder melting zone 98.

The DE 10 2011 100 456 B4 teaches that high application rates can be achieved in this way if the powdered build material is melted above the surface 18 of the substrate 14 at a distance from the melt pool 50 to an appreciable extent. However, since the laser beam 26 on the powder melting zone 98 is focused in order to melt the building material there, in the direction towards the surface 18 there is a fanning out/expansion. Conversely, the energy density on the surface 18 is further reduced, only a locally limited melt pool 50 can be produced.

With reference to the 6 and 7 will be based on the 4 and 5 a modified device 110 is illustrated. In the following, priority will be given to those features and designs that differ from those of the device 10, which according to the 1 , 4 and 5 was described above.

The device 110 is used for additive manufacturing, in particular for coating a substrate 14 that is held on a base 74 . Kinematics 76 (shown only schematically) are installed to generate the necessary relative movements. Device 110 is controlled via a control device 90.

The device 110 has a head 80 to which a first radiation source 82 for generating a laser beam 26 is assigned. In the exemplary embodiment, the optical axis 28 of the laser beam 26 is oriented essentially perpendicularly to the surface 18 of the substrate 14 to be coated, see also 7 . A powder feed 40 for providing a powder stream 42 is also assigned to the head 18 . A nozzle unit 20 directs the powder stream 42 and the laser beam 26 onto the surface 18 of the workpiece.

However, the device 110 additionally has a second radiation source 120 . In the embodiment according to 6 a head 118 is provided which is coupled to the second radiation source 120, for example via an optical fiber. The head 118 serves as an application head and can also be referred to as a supplementary head. The second radiation source 120 generates a laser beam 126 which extends along an optical axis 128 . A beam guide 124 is provided for the beam guide, for example an optical beam guide. 6 and 7 illustrate that the second radiation source 120 is also aligned with the laser beam 126 onto the surface 18 of the substrate 14. For example, the radiation sources 82, 120 are fixed to the frame, whereas the head 80 and the supplementary head 118 can be moved via the kinematics 76. Relative movements are compensated for via the light guides 84, 122, which are flexible to this extent.

In the embodiment according to 6 the heads 80, 120 are coupled together. In other words, in the exemplary embodiment, there is a mechanical connection between the housings of the radiation sources 82, 120, so that they can be moved together by the kinematics 76 during operation.

7 shows that the second radiation source 120 (cf 6 ) has a focus 130 that is significantly closer to the surface 18 of the substrate 14 than the focus 94 of the first radiation source 82. For example, the focus 130 of the second radiation source 120 is in the immediate vicinity of the surface 18 of the substrate 14. The second radiation source 120 is not aligned with the powder melting zone 98. As already explained above, the first radiation source 82 forms the powder melting zone 98 for melting the powder stream 42 in the focus 94 or in the immediate vicinity thereof. The powder melting zone 98 is spaced from the surface 18 of the substrate 14, cf 7 142 between the focus 94 and the surface 18 of the substrate 14.

The distance 142 corresponds in the exemplary embodiment according to FIG 7 also the distance between the two (at least approximately determinable) focal points (focuses) of the radiation sources 82, 120. The distance 142 is, for example, as small as possible, taking into account the structural conditions. For example, the distance 142 is less than 20 mm, for example less than 10 mm. For example, the distance 142 is less than 8 mm, for example less than 6 mm. However, the distance 142 is at least large enough for the laser beam 126 to reach the melt pool 50 as directly as possible.

The applicator head 118 of the second radiation source 120 is inclined with the optical axis 128 of the laser beam 126 relative to the optical axis 28 of the head 80 of the first radiation source 82, compare an angle designated 140 in FIG 7 . This enables the laser beam 126 to be guided directly onto the surface 18 of the substrate 14. The laser beams 26, 126 can meet there, or at least come close to one another. In this way, the laser beam 126 of the second radiation source 120 transmits its energy directly into the molten pool 50 on the surface 18 of the substrate 14. The building material that has already been at least partially melted in the powder melting zone 98 by the laser beam 26 of the first radiation source 82 passes through the powder path 100 and impinges the molten bath 50 to be deposited on the substrate 14 to form the coating 16.

In the exemplary embodiment, the angle of inclination 140 is approximately 45° (inclination between the optical axis 28 and the optical axis 128). The angle of inclination 140 is selected in such a way that the laser beam 126 does not collide with the nozzle unit 20 and/or colliding with the (main) head 80. If the structural conditions allow it, a large corresponding angle of inclination/angle of incidence in relation to the surface of the substrate (in the direction of 90°) is desirable, because in this way reflections (if the angle of incidence is too small) on the surface 18 of the substrate are minimized.

In the embodiment according to 7 1, an arrow labeled 54 describes the feed movement seen from the substrate 18 as it is moved relative to the first radiation source 82 and the second radiation source 120 to form the coating 16. FIG. The optical axis 128 of the head 118 of the second radiation source 120 is inclined to the side facing away from the coating 16 produced immediately beforehand, counter to the direction of the arrow 54.

The second radiation source 120 with the laser beam 126 is optimized to form the melt pool 50 in the desired size on the surface 18 of the substrate 14 . The first radiation source 82 with the laser beam 26 is optimized to melt the powdered construction material in the powder flow 42 as completely as possible (at least 60%, preferably at least 80%, more preferably at least 90%), so that largely melted construction material occurs on the melt pool 50. Because the molten pool 50 is now essentially generated by the second radiation source 120, its size can be selected in such a way that building material losses (overspray) are minimized. In this way, the job performance can be further increased.

8th illustrated based on the representation according to FIG 7 a modified embodiment relating in particular to the orientation of the laser beams 26,126. In 7 when the laser beam 26 is aligned substantially perpendicular (normal) to the surface 18 of the substrate 14, compare the axis 28. In contrast, in 8th both laser beams 26, 126 or both optical axes 28, 128 (of the heads 80, 118, cf 6 ) inclined relative to a normal 150 to the surface 18 of the substrate 14. The optical axis 28 is inclined at an angle 154 from the normal 150 . The optical axis 128 is inclined at an angle 158 from the normal 150 . The angles 154, 158 are, for example, in a range between 0° (or greater than 0°) and 45° in relation to the normal 150.

If one of the laser beams 26, 126 strikes the surface 18 of the substrate 14 at only a very small angle, a large part of the beam energy may be reflected. Therefore, large tilt angles with respect to the surface 18 of the substrate 14 are desirable. This results in tilt angles 154, 158 relative to the normal 150 in the range between 0° and 45°, preferably in the range between 0° and 30°. Specific structural conditions may make deviations necessary.

Also in 8th care is taken to ensure that there is only a small focus distance 142 between the focus 94 and the melt pool 50 for the laser beam 26 . Minimum distances that can be achieved result, for example, from the installation space requirements of the nozzles involved or elements for jet guidance. Furthermore, there must be enough space for the laser beam 126 so that it can reach the melt pool 50 as directly as possible.

With reference to 9 an exemplary embodiment of a method for additive manufacturing, in particular by means of laser deposition welding, is illustrated on the basis of a schematic block diagram. The process can be used, for example, to coat components.

The method includes a step S10, which relates to the provision of a first radiation source, in particular a first laser. The primary task of the first laser is to melt a powdered building material, if possible in a powder melting zone that is at a distance from the component to be coated.

A further step S12 relates to the provision of a second radiation source, in particular a second laser. The primary task of the second laser is to create and maintain a molten pool on the surface of the component to which the build material melted by the first laser is fed.

A further step S14 includes the arrangement of the first radiation source and the second radiation source, for example to provide a coating device according to the disclosure. The arrangement includes in particular an offset orientation with respect to the component to be coated (workpiece), in particular with an angular offset between the optical axes (of the application head) of the first radiation source and the second radiation source and a distance between the focal points or the foci, wherein the axis (of the applicator head) of the first radiation source, for example, serves as a reference for the distance. In other words, the first radiation source and the second radiation source are arranged, for example, in such a way that the optical axes intersect, for example in the immediate vicinity of the surface of the workpiece.

In an exemplary configuration, the first radiation source and the second radiation source are designed and arranged in such a way that areas/levels of the highest energy density are spaced apart from one another. The first radiation source is arranged, for example, in such a way that its area of highest energy density is in the powder melting zone, spaced apart from the surface of the component. The second radiation source is arranged, for example, in such a way that its area of highest energy density is directly adjacent to the surface of the component. Both the first radiation source and the second radiation source are aimed at the surface of the component, namely at the area in which the molten pool is formed during coating.

This is followed by a step S16, which includes the production of a molten bath on the surface of the component, with the power provided by the second radiation source being used primarily.

This is directly followed by a step S18, which includes feeding a powdered building material into a beam generated by the first radiation source, in particular into a powder melting zone. In this way, a significant portion of the build material is melted by the first radiation source before it strikes the molten pool.

It goes without saying that at least some of the steps S10-S18 can run in parallel, at least with a time overlap. In particular, steps S16 and S18 are carried out continuously (continuously) and largely at the same time during the coating of a component.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102011100456 B4 [0002, 0038, 0088, 0091]
• DE 112014006472 T5 [0005]

Claims (15)

Device for additive manufacturing, in particular by means of laser deposition welding - a powder feed (40) for a powdered building material, the powder feed (40) generating a powder stream (42) in the direction of a substrate (14, 64) to be coated, - A first radiation source (82) for generating high-energy radiation, in particular a first laser source, and - A second radiation source (120) for generating high-energy radiation, in particular a second laser source, the first radiation source (82) and the second radiation source (120) being offset from one another in such a way that the powdery building material supplied is initially in one of the first radiation sources ( 82) generated beam and then enters a melt pool (50) generated essentially by the second radiation source (120) on the substrate (14, 64). device after claim 1 , wherein the first radiation source (82) and the second radiation source (120) each have a beam guide (30, 124) which are arranged and configured relative to one another in such a way that the first beam guide (30) has a focus (94) which is a surface (18) of the substrate (14, 64), and that the second beam guide (124) has a focus (130) which extends from the focus (94) of the first beam guide (30) in the direction of the surface (18 ) of the substrate (14, 64). device after claim 2 , wherein the focus (130) of the second radiation source (120) of the surface (18) of the substrate (14, 64) is adjacent. device after claim 2 or 3 , wherein the powder flow (42) passes the focus (94) of the first radiation source (82), and wherein the first radiation source (82) is designed to melt the powder flow (42) in a focus area. Device according to one of Claims 1 - 4 , wherein the first radiation source (82) has a head (80) with a first optical axis (28) and the second radiation source (120) has a head (118) with a second optical axis (128), and wherein an angular offset (140) between the first optical axis (28) and the second optical axis (128). Device according to one of Claims 1 - 5 , wherein the first radiation source (82) and the second radiation source (120) are independently controllable. Device according to one of Claims 1 - 6 , wherein the alignment of the optical axis (128) of the second radiation source (120) with respect to the optical axis (28) of the first radiation source (82) is adjustable. device after claim 6 or 7 , wherein at least one focal distance (142) of at least the first radiation source (82) or the second radiation source (120) in relation to the substrate (14, 64) is adjustable. Device according to one of Claims 6 - 8th , The power of at least the first radiation source (82) or the second radiation source (120) being adjustable. Device according to one of Claims 1 - 9 , wherein the first radiation source (82) and the second radiation source (120) are each designed as lasers for generating a laser beam (26, 126), and wherein the first radiation source (82) and the second radiation source (120) operate at different power levels operate. device after claim 10 , wherein the first radiation source (82) is operated with a laser power which has a ratio to the laser power of the second radiation source (120) which is in the range from 2.0:1 to 10.0:1, in particular in the range from 3.0:1 to 6.0:1 is, and in particular is in the range of 4.0:1 to 6.0:1. device after claim 10 or 11 , wherein the laser power of the first radiation source (82) is in the range between 3.0 kW and 20 kW. Device according to one of Claims 1 - 12 , wherein the optical axis (28) of the first radiation source (82) is oriented perpendicular or essentially perpendicular to the surface (18) of the substrate (14, 64) to be coated, and wherein the optical axis (128) of the second radiation source (120) is oriented perpendicularly or essentially perpendicularly to the surface (18) of the substrate (14, 64) to be coated. Method for additive manufacturing, in particular by means of laser deposition welding, comprising the following steps: - providing a first radiation source (82), in particular a first laser, - providing a second radiation source (120), in particular a second laser, - arranging the first radiation source (82) and the second radiation source (120) in a mutually offset orientation in relation to a substrate (14, 64), - generating a melt pool (50) on the substrate (14, 64), in particular with the second beam ment source (120), and - supplying a powdered building material in a beam generated by the first radiation source (82), in particular to a focus (94) of the first radiation source (82), the building material melted by means of the first radiation source (82) being fed into the by means of the second radiation source (120) generated melt pool (50) occurs. procedure after Claim 14 , wherein the first radiation source (82) and the second radiation source (120) are tilted relative to one another, and wherein the first radiation source (82) and the second radiation source (120) are arranged in such a way that the focus (94) of the first radiation source (82 ) is spaced from a surface (18) of the substrate (14, 64), and that the focus (130) of the second radiation source (120) extends from the focus (94) of the first radiation source (82) in the direction of the surface (18) of the substrate (14, 64).

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