RU2784612C1 - System and method for repairing high-temperature gas turbine components - Google Patents

Abstract

FIELD: component forming.

SUBSTANCE: method for forming a component includes mixing a powdered base material and a binder to form a mixture, molding the mixture to a desired shape without melting the base material, removing the binder from the desired shape to form a carcass, wherein the volume of the carcass is between 80 percent and 95 percent of the base material, and impregnating the scaffold with the melting point depressant material to form a finished component, the finished component having less than one percent porosity by volume.

EFFECT: improvement in the quality of repair is achieved.

15 cl, 22 dwg

Description

Technical field

[0001] The present disclosure is directed generally to a system and method for repairing high temperature gas turbine components, and more particularly to such a system and method for repairing gas turbine blades and guide vanes.

Background of the invention

[0002] The difficulties associated with the additive manufacturing (AM) of nickel-based gas turbine components with a high content of gamma-prime phase make the process unsuitable for large-scale fabrication or repair. In particular, attempts to additively manufacture components using (CM) 247 alloy or repair such components often result in grain boundary melting and cracking. Alternatively, the components are repaired with a different, inferior nickel-based alloy that is less prone to cracking, resulting in poor component performance.

The essence of the invention

[0003] A method for forming a component includes mixing a powdered base material and a binder to form a mixture, molding the mixture to a desired shape without melting the base material, removing the binder from the desired shape to form a skeleton, wherein the volume of the skeleton is between 80 percent of the base material and 95 percent, and impregnating the scaffold with a melting point depressant material to form a finished component, the finished component having less than 1 percent porosity by volume.

[0004] In another design, the component includes a scaffold formed from a base material that defines the final shape of the component, the scaffold having a porosity between 5 percent and 20 percent, and a melting point depressant material located in the scaffold that fills pores in the scaffold to form a finished component having less than 1% porosity by volume.

[0005] The foregoing has set forth the technical features of the present disclosure broadly enough to enable those skilled in the art to better understand the following detailed description. In the following, additional features and advantages of the disclosure that are the subject of the claims will be described. Those skilled in the art should appreciate that they can easily use the concept and the disclosed specific embodiments as a basis for modifying or designing other structures to achieve the identical purposes of the present disclosure. Those skilled in the art should also appreciate that such equivalent constructions do not depart from the spirit and scope of the disclosure in its broadest sense.

[0006] In addition, before reading the detailed description below, it should be understood that various definitions of certain words and expressions are given in this description, and those skilled in the art should understand that such definitions apply in many, if not most, cases in the previous , as well as future uses of the words and expressions thus defined. Although some terms may cover a wide range of options, the appended claims may expressly limit these terms to specific options.

Brief description of the drawings

[0007] FIG. 1 is a longitudinal sectional view of a gas turbine engine.

[0008] FIG. 2 is a perspective view of several guide vanes of the gas turbine engine of FIG. one.

[0009] FIG. 3 is a perspective view of an insert for use in repairing the turbine guide vane of FIG. 2.

[0010] FIG. 4 is a perspective view of the guide vanes of FIG. 2 with the insert according to FIG. 3.

[0011] FIG. 5 is a perspective view of a near-final 3D printed component.

[0012] FIG. 6 is a perspective view of the component frame after debinding and sintering.

[0013] FIG. 7 is a perspective view of the frame of the component during infiltration of a melting point depressant.

[0014] FIG. 8 is a perspective view of a finished component close to its final shape after infiltration.

[0015] FIG. 9 is a perspective view of another component obtained by three-dimensional (3D) printing with a near-final shape.

[0016] FIG. 10 is a perspective view of the frame of the component of FIG. 9 after debinding and sintering.

[0017] FIG. 11 is a perspective view of the frame of the component of FIG. 9 during infiltration of the melting point depressant.

[0018] FIG. 12 is a perspective view of the finished component in close to final shape after infiltration and during removal of the restrictor.

[0019] FIG. 13 is a perspective view of an attached PVD for use in the lead edge repair process.

[0020] FIG. 14 is a perspective view of a replacement leading edge component attached to the attachable PS of FIG. 13.

[0021] FIG. 15 is a perspective view of a portion of a gas turbine blade having functional damage in the form of end corrosion and end cracking.

[0022] FIG. 16 is a perspective view of the blade of FIG. 15 with the damaged portion of the blade removed.

[0023] FIG. 17 is a perspective view of a replacement end for repairing the damaged blade of FIG. 16.

[0024] FIG. 18 is a perspective view of an attached PVD for use in repairing the blade end of FIG. 16.

[0025] FIG. 19 is a perspective view of the damaged blade of FIG. 16 attached to the PSZ according to FIG. 18 and the replacement end of FIG. 17.

[0026] FIG. 20 is a perspective view of a replacement end in a "green billet" during the manufacturing process.

[0027] FIG. 21 is a perspective view of the replacement end of FIG. 20 after sintering and removal from the technological support element.

[0028] FIG. 22 is a perspective view of the replacement end of FIG. 21 mounted on the blade of FIG. 16.

[0029] Before any embodiments of the invention are explained in detail, it should be understood that the invention is not limited in its application to the details of construction and arrangement of components set forth in the description below or illustrated in the accompanying drawings. The invention is capable of other embodiments and may be practiced or carried out in various ways. In addition, it should be understood that the language and terminology used herein is for the purpose of description only and should not be construed as limiting.

Detailed description

[0030] Various technologies are described below, which relate to systems and methods, with reference to the drawings, in which like reference numbers represent like elements throughout the description. The drawings discussed below and the various embodiments used to describe the principles of the present disclosure in this patent document are provided by way of illustration only and should in no way be construed as limiting the scope of the disclosure. Those skilled in the art will appreciate that the principles of the present disclosure may be implemented in any suitably implemented equipment. It should be understood that functionality that is described as being performed by certain elements of the system may be performed by multiple elements. Similarly, for example, an element may be configured to perform functionality that is described as being performed by multiple elements. In the following, numerous innovative ideas of the present application will be described with reference to exemplary non-limiting embodiments.

[0031] In addition, it should be understood that the words or expressions used here should be construed in a broad sense, unless they are clearly limited in some examples. For example, the terms "including", "having" and "comprising", as well as their derivatives, mean inclusion without limitation. The singular forms are also intended to include the plural forms, unless the context clearly indicates otherwise. Additionally, the term "and/or" as used herein means and encompasses any and all possible combinations of one or more of its associated listed elements. The term "or" is inclusive, meaning "and/or" unless the context clearly indicates otherwise. The expressions "associated with" and "associated with" and their derivatives may mean to include, be included in, interconnect with, contain, be contained in, connect to or with, conjugate with, communicate with, interact with, intersperse, to be placed next to, to be near, to be (under) connected with or to, to have, to have the property of something, or the like. In addition, although multiple embodiments or designs may be described, any features, methods, steps, components, etc. described with respect to one embodiment are equally applicable to other embodiments, unless specifically stated to the contrary.

[0032] In addition, although the terms "first", "second", "third", etc. may be used here to refer to various elements, details, functions, or actions, those elements, details, functions, or actions are not to be limited by these terms. Instead, these numbers are used to distinguish different elements, details, functions, or activities from one another. For example, the first element, information, function, or action may be referred to as the second element, information, function, or action, and similarly, the second element, information, function, or action may be referred to as the first element, information, function, or action, without departing from the scope. of this disclosure.

[0033] In addition, the term "adjacent" can mean: that an element is relatively close to, but not in contact with, another element; or that the element is in contact with another site, unless the context clearly indicates otherwise. Further, the expression "based on" is intended to mean "at least partially based on", unless explicitly stated otherwise. The terms "about" or "practically" or similar terms are intended to cover deviations in value that are within normal industry manufacturing tolerances for that size. If there are no industry standards available, a 20 percent deviation should fall within the meaning of these terms, unless otherwise noted.

[0034] FIG. 1 illustrates a gas turbine or gas turbine internal combustion engine 10 that includes a compressor section 15, a combustion section 20, and a turbine section 25. During operation, atmospheric air is drawn into the compressor section 15 and compressed. A portion of the compressed air is mixed with fuel and combusted in the combustion section 20 to produce high temperature combustion products. The combustion products mix with the remaining compressed air to form exhaust gases, which then pass through the turbine section 25. The exhaust gases expand in the turbine section 25 creating torque which drives the compressor section 20 and any ancillary equipment connected to the engine 10, such as an electrical generator. Exhaust gases enter the turbine section 25 at a high temperature (1000 degrees Fahrenheit, 538 degrees Celsius or more), so that the rotor and guide vanes 30 of the turbine are exposed to high temperatures and must be made of materials suitable for these temperatures. The terms "vane" and "guide vane" are to be considered interchangeable. Although typically the term "vane" refers to rotating airfoils and "guide vane" to fixed airfoils, the invention should not be limited to these definitions since most repairs or processes apply equally to rotors and guides. shoulder blades.

[0035] In one design, the guide vanes 30 are made from a nickel-based superalloy, such as Alloy (CM) 247. FIG. 2 illustrates a portion of the fixed guide vanes 30 from the turbine section 25 of the engine 10 of FIG. 1. Each blade 30 includes an inlet edge 35, an outlet edge 40, a back 45, and a trough 50. Adjacent blades 30 interact with each other to form a flow path. The exhaust gases pass through these flow paths and are directed and accelerated in the desired manner to effectively expand the exhaust gases and provide torque to the rotor 53, which in turn drives the auxiliary equipment.

[0036] During operation, the blades 30 may become damaged. Damage may be caused by foreign object impact, high temperature operation, fatigue, creep, oxidation, and the like. One area that is susceptible to damage is the leading edge 35 of the blade 30. FIG. 2 illustrates one of the blades 30 with a portion 55 of the leading edge 35 removed. A desirable repair would include replacing the removed portion 55 with material that closely matches the base material. However, nickel-based superalloys such as those used to make blades 30 are not suitable for welding or typical additive manufacturing repair processes.

[0037] FIG. 3 and 4 illustrate one possible repair to the leading edge 35 of the blade 30 illustrated in FIG. 2. FIG. 3 illustrates an insert in the form of an insert 60 at the leading edge, and FIG. 4 illustrates the positioning of insert 60 at the leading edge in attachment vane 30. Insert 60 includes a significant portion of matching base material and is typically attached using a brazing process.

[0038] FIG. 5-12 illustrate the manufacturing process of the insert 60 illustrated in FIG. 3, or any other desired repair component. Fig. 5-8 illustrate this process for a generic cube object 65, while FIG. 9-12 illustrate a similar process for the leading edge insert 60 illustrated in FIG. 3.

[0039] The process begins by mixing the high gamma prime nickel phase (base material) nickel powder 66 with the binder 67 and 3D printing or otherwise additively manufacturing the green billet of the desired component 70, 75 to near final shape. Thereafter, the green piece of component 70, 75 is allowed to dry. Fig. 5 and 9 illustrate this stage. During the printing or additive manufacturing process, the base material is not melted. As used herein, "near-final shape" means that a component falls within the desired process parameters and tolerances for that component at a particular stage in the manufacturing process without additional machining. However, some surface grinding or polishing may be required in order to achieve the desired finish or surface texture in the final component. In addition, additional layers or coatings may be applied to the component in order to complete the component for use. In addition, as illustrated in FIG. 9-12, the green body of component 75 may include features such as stops 80 or support structures that are used during the manufacturing process and then removed. A green piece of component 75 incorporating features such as those indicated would be considered to be close to final shape since no additional machining or other processing is required prior to performing the additional manufacturing steps, only the removal of unwanted features (limiter 80) is required.

[0040] The next step is to place the green component 70, 75 in an oven or other heating device. The green stock of component 70, 75 is heated to burn out or remove binder 67. The remaining material forms a framework 85, 90 consisting of base material 66 and gaps or voids 68 previously occupied by binder 67. FIG. 6, frame 85 has a cuboid shape. In FIG. 10, carcass 90 forms an intermediate component that will eventually become insert 60 at the leading edge and further includes a stopper 80. In preferred embodiments, the heating or sintering step does not melt base material 66 and leaves at least eighty percent of carcass 85,90 volume. of base material 66, thereby leaving no more than twenty percent of the carcass 85, 90 as empty space 68. This is referred to here as twenty percent or less porosity. The amount of binder 67 used and the sintering temperature are chosen to achieve less than twenty percent porosity, and preferably five to twenty percent porosity.

[0041] As illustrated in FIG. 7 and 11, the frame 85, 90 and the stopper 80 are impregnated (infiltrated) with a low melting point material, or melting point depressant 100 (sometimes referred to as "solder"). Preferred compositions of the melting point depressant 100 include at least one of titanium (Ti), zirconium (Zr), and hafnium (Hf), with the balance being chromium (Cr) and nickel (Ni). The use of boron (B), silicon (Si) or phosphorus (P) in part or in full as a melting point depressant 100 is excluded in order to prevent the negative effects that these materials have on the material properties of the finished component 60, 65.

[0042] To obtain the desired impregnation, the melt point depressant 100 is melted in a manner that ensures that the liquid melt point depressant 100 is in contact with the scaffold 85, 90. The capillary action created by the porosity in the scaffold 85, 90 draws the liquid pour point 100 melting temperature into the pores 68 of the framework 85, 90 and can result in a finished component 60, 65 that is ninety-nine percent filled with material (ie, one percent porosity).

[0043] The specific composition of the melting point depressant 100 is selected at least in part based on the amount of titanium included in the base material. For example, in designs that include 3.5 percent or more titanium by weight in the base material, the desired melt point depressant 100 includes at least one of Hf and Zr, with the remainder being Ni and Cr. In designs with 1.0 percent or less Ti in the base material, the preferred composition is Ti and the remainder is Ni and Cr. When the amount of Ti in the base material is between 1.0 percent and 3.5 percent, the desired composition includes at least one of Zr and Ti, and the rest is Ni and Cr. The amount of Ti, Zr, or Hf is chosen such that the finished nickel-based component has less than 6.0 percent Ti (with other designs below 5.0 percent, and still others below 4.0 percent).

[0044] Once the impregnation is complete, any features added for manufacturing requirements, such as the stop 80 or support structure illustrated in FIG. 9-12 are removed to complete component 60, 65. Any additional sanding, polishing, or layering may now be performed before component 60, 65 is installed, as illustrated in FIG. 4. In preferred designs, after impregnation, component 60, 65 has less than one percent porosity.

[0045] The process described here does not melt the base material powder 66. Instead, powder 66 is mixed with binder 67, 3D printed using a laser or other energy source, and dried. Burn binder 67 at low temperature (eg <500°C). The remaining base material 66 is heated to a sintering temperature which ensures that a maximum of twenty percent porosity remains in the sintered material.

[0046] For nickel-based alloys, the amount of titanium used is preferably limited to about six percent (ie, between four and eight percent) to reduce the chance of reduced mechanical properties. Because of this limitation, the level of porosity in the carcass 85, 90 is determined at least in part by the amount of titanium in the base material and in the solder 100 (sometimes referred to as a melt point depressant), with the target being approximately six percent titanium in the finished component 60, 65. For example, in one design, the base material or frame 85, 90 may not include titanium. If solder is used that contains 22% titanium, then the total porosity of the framework 85, 90 must be limited to about 30%, resulting in a finished component 60, 65 with about 6.6% titanium.

[0047] In another example, the frame 85, 90 includes 1% titanium. In this case, using an identical solder with 22% titanium, the carcass 85, 90 must be limited to less than 20% viscosity in order to achieve a finished component 60, 65 having about 5.2% titanium.

[0048] In yet another example, the frame 85, 90 includes 2% titanium. In this case, using an identical solder with 22% titanium, the carcass 85, 90 must be limited to less than 15% viscosity in order to achieve a finished component 60, 65 having about 6.0% titanium.

[0049] As explained, nickel-based gas turbine components, in particular alloy (CM) 247 components, are difficult to repair or build up in any way that involves melting the component, because the melting temperature of the grain boundaries (melt onset) is low relative to the welding temperature, so welding repairs often cause cracks during the repair process.

[0050] As explained with respect to FIG. 2-12, one alternative to welding repair is to first build a replacement component 60, 65 (pre-sintered billet (PSB)) for the damaged blade section 30 and then attach this new replacement component 60, 65 to the component being repaired (e.g., a blade). 30) using a process that guarantees a maximum temperature that remains below the melting point of the grain boundaries. To further improve this repair, it is possible to replace the damaged portion of the repaired component with a replacement component 60, 65 that includes a functional material that provides higher oxidation resistance than the base material of the repaired component (eg, blades 30).

[0051] The damaged area 55 is removed and replaced with a close-fitting replacement component 105 made using additively manufactured (AM) material or pre-sintered billet (PSB) that provides similar or better oxidation and degradation properties. When the replacement component 105 is a replacement for the leading edge 35, as illustrated in FIG. 2-4 and 9-12, additively produced replacement components 105 may include columnar grains with significant fracture resistance.

[0052] In order to repair the leading edge 35 with a high oxidation resistance material, the damaged portion 55 of the leading edge 35 of the blade 30 is first removed. The removed damaged portion 55 is measured to determine the size and configuration of the replacement component 105 to be installed. The replacement component 105 is then fabricated using an additive manufacturing process or as a PSZ, such as a PSZ made using the process described with respect to FIG. 2-12. In order to improve the oxidation resistance of the replacement component 105, the material used to make it using the additive manufacturing process includes up to eight percent (8%) aluminum. In addition, fastening structures 110, such as pins, protrusions, recesses, holes, etc., may be provided as part of the replacement component 105 to increase or create mutual engagement between the replacement component 105 and the blade 30 or other repairable component.

[0053] When the replacement component 105 is made in the form of PSZ, the preferred material includes up to eighty percent (80%) superalloy (preferably matching the repaired blade 30), up to eight percent (8%) aluminum, and up to thirty percent (30% ) solder, including Ti, Zr and Hf, as described above. Similar to the additively produced replacement component 105, the replacement-PSZ components 105 may include mounting structures 110 such as those described above. Fig. 9 and 10 illustrate attachment structures 110 in the form of alignment pins 111. Pins 111 mate with and fit into holes formed in blade 30 to which replacement component 105 will attach. Although pins 111 are illustrated only in FIG. 9 and 10 for clarity, in the preferred designs, pins 111 would be formed as part of replacement component 105 and would therefore be present at every step of the manufacturing process. In other designs, the pins 111 are separate components that are attached to the replacement component 105 at some point during its manufacture. Attachment could be facilitated using any suitable attachment means including, but not limited to, adhesives, welding, brazing, etc.

[0054] The material used to make the replacement component, PSZ 105, is maintained at a temperature of at least 50 degrees Celsius above the melting point of the solder for more than one hour to allow most of the solder to react with the base material powder. This prevents remelting during the brazing operation attaching the replacement component 105 to the blade 30.

[0055] Attachable PSZ 115 shown in FIG. 13 is formed from a material combination similar to that described above for the replacement component-PSZ 105, except that it includes at least thirty percent (30%) solder rather than up to thirty percent (30%) solder. Attachable PSZ 115 preferably has a thickness of no more than 250 microns and is made at the same temperature as replacement PSZ 105 described above, but held at that temperature for a shorter time (less than 15 minutes). The attached PSW 115 therefore has enough unreacted solder to be able to attach the replacement component 105, as illustrated in FIG. 14, regardless of how it is made (PSZ or additive manufacturing), to the repairable blade 30.

[0056] The replacement component 105 has sufficient mechanical properties and oxidation resistance due to its adjusted composition and Ni-Cr-(Ti, Zr, Hf) solder composition. In addition, when using the additively produced replacement component 105, the columnar grains provide significant fracture resistance relative to the base material with an equiaxed grain structure.

[0057] As will be described below, these processes and procedures may be applied to other components, such as end face 120 of guide vane 30 or rotor blade.

[0058] For example, FIG. 15-19 illustrate a process similar to the above, but for repairing the end face 120 of a nickel-based gas turbine guide or rotor blade 30, and in particular a guide or rotor blade 30 made from alloy 247 or a similar material.

[0059] FIG. 15 schematically illustrates blade 30 with end section cracks 125 that extend downward into blade 30. Blade end 120 also includes oxidation damaged areas 130 that may be common after operation of turbine blade 30. To repair the blade 30, the damaged portion of the end face 120 is first removed. In the example of FIG. 15, the removal of the damaged area 135 does not completely remove the cracks 125, but the oxidation damaged areas 130. It is desirable to minimize the amount of end face 120 removed so that in some circumstances areas with a crack or cracks 125 may remain after removal. With reference to FIG. 16, any cracks 125 that remain after removal of the damaged portion 135 are removed using a machining, grinding, or other suitable material removal process.

[0060] A tight-fitting replacement end 140 is formed to fill the space created by the removal of the damaged portion 135. The replacement end 140 may also fill any spaces created during the removal of any cracks 125. Alternatively, the space opened up during the removal of cracks 125 may be filled with solder powder during the attachment process of replacement end 140. Replacement end 140 may be formed using an additive manufacturing (AM) process or may be formed from a pre-sintered billet (PSB) that provides similar or better oxidation and degradation properties than the removed portion. 135.

[0061] The replacement end 140, when manufactured using the AM process, preferably consists of a material similar to the base material of the blade 30 with up to eight percent (8%) aluminum added to provide excellent oxidation resistance. In addition, fastening structures 110 such as pins 145 illustrated in FIG. 17 in order to improve the mechanical connection between the replacement end 140 and the rest of the repaired blade 30. Of course, other features such as projections, holes, bosses, etc., can be used as attachment structures 110. The pins 145 of FIG. 17 are inserted into appropriate holes made or otherwise present in the remainder of the repaired blade 30.

[0062] In designs where the AM-derived replacement end 140 is replaced with a PSZ, the material is preferably made from up to eighty percent (80%) superalloy (matching the base material of the repaired blade 30), up to eight percent (8%) aluminum and up to thirty percent (30%) of solder including Ti, Zr and Hf as described above.

[0063] The material used to make the replacement end-PSZ 140 is maintained at a temperature of at least 50 degrees Celsius above the melting point of the solder for more than one hour to allow most of the solder to react with the base material powder. This prevents remelting during the brazing operation attaching the replacement end 140 to the blade 30 being repaired.

[0064] Attachable end face 150 shown in FIG. 18 is formed from a material combination similar to that described above for replacement end-PSZ 140, except that it includes at least thirty percent (30%) solder rather than up to thirty percent (30%) solder. Attachable end-end 150 preferably has a thickness of no more than 250 microns and is made at the same temperature as the replacement end-end 140 described above, but maintained at that temperature for a shorter period of time (less than 15 minutes). The attached end face 150 therefore has enough unreacted solder to be able to attach the replacement end 140 to the repaired blade 30, as illustrated in FIG. 19, regardless of how the replacement end 140 is made (PSD or additive manufacturing).

[0065] The replacement end 140 has sufficient mechanical properties and oxidation resistance due to its adjusted composition and Ni-Cr-(Ti, Zr, Hf) solder composition.

[0066] As explained above, gas turbine components operate under a wide variety of local conditions that can produce localized damage. This can be attributed to differing component states (eg, temperatures, pressures, fluid properties, etc.) and engine states.

[0067] One example of local operating conditions exists in the first row turbine blade 155, where localized failure of the blades 155 can cause damage in several areas, including the leading edge 160 of the blade 155 and the tip 165 of the blade 155. FIG. 22 illustrates the leading edge 160 and end face 165 of the blade 155, and also illustrates a replacement end face 170 installed in order to repair damage due to cracking and/or oxidation on the end face 165 of the blade.

[0068] One type of damage occurs at the leading edge 160 of the first stage blade 155, as well as other blades, where the ceramic coating adheres adjacent to the cooling hole sequence 175. If the coating breaks, burnt or loss of the leading edge is often observed. Another area where damage may occur is at end 165 of blade 155, where blade 155 may rub against an annular segment of the shroud or other component radially outward relative to blade 155. At end 165 of blade 155, severe oxidation and cracks or end cracks may also occur. may form and spread from the cooling holes 175 or from damage caused by other factors such as friction or oxidation.

[0069] As discussed above, repairs to the rotor or guide vane ends 165 may include removing a portion of the blade end 165, followed by replacement with a replacement end 170. Similar repairs may also be made to the leading edges 160 of the rotor or guide vanes.

[0070] Additive manufacturing can be relied upon to make replacement components or replacement ends 170 using brazing processes and specialty solders that enhance the performance of the repaired vane or guide vane 155.

[0071] One preferred additive manufacturing process well suited for making replacement components or replacement ends 170 involves atomic diffusion. Fig. 20-22 illustrate the process of repairing a blade end 165 using atomic diffusion to form a replacement end 170. As those skilled in the art will appreciate, the same process can be applied to repair the leading edge 160 of a blade or guide vane 155, as well as others not discussed here. components.

[0072] With reference to FIG. 20, atomic diffusion uses binders and metal powder to rapidly build a three-dimensional shape. The metal powder is typically selected to closely match the material (eg, Alloy (CM) 247) used in the repaired component (ie, blade 155). The metal powder and polymeric binder are mixed and then molded to the desired shape, which will eventually result in a replacement component or end 170. This pre-component 185 is often referred to as "green stock". This "green billet" of component 185 is then heated and sintered in a high temperature sintering operation to remove the binder and mechanically/metallurgically bond the powder particles. The sintering temperature is chosen to completely remove the binder while providing the desired mechanical/metallurgical bonding of the powder metal without completely melting the metal particles of the powder.

[0073] One method for forming the green body of component 185 includes a 3D printing technique. Prepare the raw material in the form of wire, including the desired powdered metal and a binder. The user is able to combine material chemistries or select chemistries in the manner desired to achieve the desired material properties in the finished replacement end 170 or finished replacement part. In addition, different compositions may be used at different times during the formation of replacement end 170 to achieve different properties at different locations in replacement end 170. For example, in one design, the composition intended to be the first or boundary layer includes the desired base materials, as well as solder integrated into the raw material in the form of wire.

[0074] To make a replacement end 170 or other component, a first or boundary layer is deposited on the support structure 190 or formed independently of the support structure 190. The first layer in the example of FIG. 20 is intended to be the surface that mates with or is soldered to the repaired component (i.e., blade 155), attaching replacement end 170 to repaired blade 155. Additional layers may be formed on top of the first layer using an identical material, or a different material may be used. material that may be required for a specific replacement component.

[0075] For example, the raw material may be changed to a second material that does not include solder, but instead more closely matches the base material of the blade 155 or other repairable component. As explained above, some materials may be used that enhance the performance of the replacement end 170 or other component over that of the base material. Also, any of these materials can be used in this process. For example, up to 8% aluminum can be used to improve oxidation resistance. As noted above, the sintering process is designed so as not to melt the powder material. Because this process is a non-melting process, no variation in chemical composition is expected.

[0076] With further reference to FIG. 20, metal powder is extruded with a binder (e.g., a polymer) to create a wire feed stock that is then deposited onto support structure 190. Between the deposited material and support structure 190, a ceramic interlayer 195 may be placed to assist in the removal of the finished replacement. end 170 with support structure 190. The step of washing the green billet removes the resin binder and compaction is performed by sintering. Typically, densities greater than ninety-six percent can be achieved, but this depends on the size of the component and the corresponding wall thickness, as compaction is achieved by solid state diffusion. Examples of replacement ends 170 formed using this process after sintering and removed from the support structure are illustrated in FIG. 21.

[0077] This method does not suffer the isotropy of stratified AM methods and, due to its rate of green component 185 production and very low powder waste, significantly reduces costs compared to other AM methods. In addition, as noted above, this additive manufacturing process may be used to form components other than replacement ends 170, including replaceable leading edges or other components, and may include additional features such as fastener structures 110.

[0078] Another benefit of this approach is that components can be made from other high temperature resistant (heat resistant) materials (e.g., oxide dispersion strengthened (ODS) or advanced single crystal (CMSX8/Rene N5/PWA1484)), which have the best strength, oxidation resistance and coating adhesion.

[0079] In general terms, FIG. 20-22 illustrate replacement end 170 during various states of manufacture using an atomic diffusion process. After removal of the damaged section of the end face 165 of the repaired blade 155, the replacement end face 170 can be sized for manufacture. In many cases, a support structure 190 will be required to form a load-bearing base on which a replacement end 170 can be formed. end 170 from the support structure 190.

[0080] The green piece of component 185 is then printed using a raw material of the appropriate component composition. The first layer or first few layers may use a raw material that is part base material, part binder and part solder, which is ultimately used during the attachment of the replacement end 170 to the blade 155. After these initial layers are printed, this raw material can be switched to another feedstock that includes the desired base metal chemistry (ie, a chemistry that closely matches blade 155) and a binder, often in the form of a polymer. The chemical composition of the subsequent feedstock may have an improved chemical composition, as discussed above, to provide superior material properties such as oxidation resistance.

[0081] Upon completion of the 3D printing process, the green stock of component 185 is washed and sintered to remove the binder and mechanically or metallurgically bind the remaining particles into the desired shape. The sintered replacement end 170 is removed from the support structure 190 as illustrated in FIG. 21.

[0082] As illustrated in FIG. 22, the replacement end 170 is placed in position on the blade 155 and a solder joint 200 is formed therebetween. During the brazing process, the solder in the initial layer or layers of the replacement end 170 aids in the formation of the solder joint and the attachment of the replacement end 170.

[0083] Existing materials used for pre-sintered billets (PSBs) and for high temperature solders for use with nickel-based superalloy materials that operate in high temperature environments (e.g., 1000 degrees Fahrenheit, 538 degrees Celsius) are typically made based on nickel (Ni) chromium (Cr).

[0084] The composition described here is preferably applied to PSZ and/or solders that do not contain boron. Rhenium (Re) or ruthenium (Ru) can be added to most nickel-based solder alloys to increase the creep life of boron-free PSZ and solder alloys. These two elements are powerful creep enhancers that are added to the base metal composition to extend life before creep failure. They increase the creep resistance of nickel-based alloys by up to ten times. Their high melting point and large atomic diameter result in low atomic diffusion rates and allow Ni-based materials to increase their creep resistance.

[0085] Rhenium (Re) and ruthenium (Ru) have not been added to boron free solders to date because the need for creep resistant solders has not been known.

[0086] To add Re or Ru, the materials are converted into a powder form and then mixed with the base material powder mixture before high temperature brazing. Re and Ru are added to the Ni-Cr-X boron free solder/base material powder mix prior to making the PSZ. Preferably, Re and Ru have the smallest particle size possible for the powder. It is preferable that the particle diameter of the Re and Ru powder be at least 50% or less than that of the base metal and the solder metal powder to ensure even mixing and homogeneous distribution of the elements after brazing. Re and Ru powders do not melt during the brazing process. Instead, they diffuse into the surrounding liquid solder during high temperature soldering. Since the diffusion rates in the liquid are high, these elements are evenly spaced apart in the solder.

[0087] Re and Ru are added such that they make up 3-6 percent of the total composition of the solder or PSZ regardless of the proportion of base metal to solder powder in the solder.

[0088] For example, when repairing a component made from Alloy 247, a PSW can be used that is made from powders that are 74-77 percent match the composition of alloy 247, 20 percent match the desired solder (sometimes called a "melting point depressant") , and 3-6 percent are one or both of Re or Ru.

[0089] Suitable solders are typically nickel-based and include nickel, chromium, and at least one of titanium, zirconium, and hafnium. Some special solder formulations include a formulation that includes 6.5% Cr, 11% Zr, 7.5% Ti, and the rest Ni. Another composition may include 5.0% Cr, 10% Hf, 10% Zr, and the rest Ni. Yet another composition may include 17% Cr, 22% Ti, and the rest Ni.

[0090] Each of the three components - base material (74-77 percent), solder (20 percent) and Re or Ru (3-6 percent) - is powdered and mixed together for sintering. During any melting steps (ie brazing processes) Re and Ru do not melt. On the contrary, during the melting process they are dispersed throughout any baths of the melt.

[0091] FIG. 3 illustrates one possible PSZ insert 60 that could be made using the materials described above. PSZ insert 60 is preformed and sintered including base material, solder and the desired amount of Re or Ru. Fig. 4 illustrates the repair of a turbine blade 30 using the PSZ insert 60 illustrated in FIG. 3. After the damaged portion of the blade 30 has been removed, the desired PSZ insert 60 is sized and manufactured as described. The PSZ insert 60 is then positioned in the void space 55 in the blade 30 and soldered in place. During the brazing process, some of the Re and Ru migrate into the molten solder. Re and Ru will not melt in the molten bath, but will instead be embedded in the solder during solidification.

[0092] While an exemplary embodiment of the present disclosure has been described in detail above, those skilled in the art will appreciate that various changes, substitutions, variations, and improvements may be made to the embodiment disclosed herein without departing from the spirit and scope of the disclosure in its broadest sense.

[0093] No portion of the description in this application should be taken as implying that any particular element, step, act, or function is an essential element that should be included in the scope of the claims: the scope of the patentable subject matter of the invention is determined only by what is given in the patent the claims of the invention. In addition, none of the claims does not imply the construction of the claim "means plus function", unless after the words "means for" there is an indication of the corresponding function.

Claims (21)

1. A method for forming a component, including: mixing the powdered base material and the binder to form a mixture; molding the mixture to the desired shape without melting the base material; removing the binder from the desired shape to form a carcass having a volume containing between 80 percent and 95 percent base material; and impregnating the scaffold with a melting point depressant material to form a finished component, the finished component having a porosity of less than one percent by volume. 2. The method of claim 1 wherein the desired shape is heated to burn out the binder without melting the base material. 3. The method of claim 1, wherein the melting point depressant consists essentially of Ni, Cr and at least one of Ti, Zr and Hf. 4. The method of claim 1 wherein the melting point depressant consists essentially of 6.5% Cr, 11% Zr, 7.5% Ti and the remainder Ni. 5. The method of claim 1 wherein the melting point depressant consists essentially of 5.0% Cr, 10% Hf, 10% Zr and the remainder Ni. 6. The method of claim 1, wherein the melting point depressant consists essentially of 17% Cr, 22% Ti, and the balance Ni. 7. The method of claim 1 wherein the finished component is a portion of the leading edge of a turbine blade. 8. The method of claim 1, wherein the melting point depressant contains an amount of Ti selected such that the component contains between 4% and 6% titanium. 9. The method of claim 1, wherein the desired shape is chosen to replace the damaged portion of the leading edge of the turbine blade. 10. The method of claim 1, wherein the desired shape is chosen to replace the damaged end portion of the turbine blade. 11. Component containing: a frame formed from the base material and defining the final shape of the component, and the frame has a number of pores and a porosity between 5 percent and 20 percent; a melting point depressant material located in the framework that fills pores in the framework to form a finished component having a porosity of less than 1 percent by volume. 12. The component of claim 11 wherein the melting point depressant consists essentially of Ni, Cr and at least one of Ti, Zr and Hf. 13. The component of claim 11 wherein the melting point depressant consists essentially of 6.5% Cr, 11% Zr, 7.5% Ti and the remainder Ni. 14. The component of claim 11 wherein the melting point depressant consists essentially of 5.0% Cr, 10% Hf, 10% Zr and the balance Ni. 15. The component of claim 11 wherein the melting point depressant consists essentially of 17% Cr, 22% Ti and the remainder Ni.

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