JP2016516580A - Method of remelting and repairing superalloy by laser using flux - Google Patents

Abstract

The present invention relates to a method for repairing surface cracks (92) caused by the use of a superalloy component (90). Powdered flux material (100) is applied above the crack and melted by the laser beam (98) to form a remelted region (104) of superalloy material below the slag layer (106). The slag cleans the molten pool of contaminants trapped in the crack, eliminating the need for pre-weld fluoride ion cleaning. In addition, the alloy material can be applied with a powdered flux material to increase the melt volume of the remelt zone or to change the composition.

Description

  This application is a continuation-in-part of pending US Patent Application No. 13/005656 filed on January 13, 2011 (US Patent Application Publication No. 2012/0181255). The disclosure of the US patent application is hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION The present invention relates generally to the field of metal bonding, and specifically to the repair of superalloy materials.

BACKGROUND OF THE INVENTION After being used in a gas turbine engine, hot gas path components such as blades and vanes often have narrow saddle-shaped cracks known as craze cracks. Repair of such cracks is difficult because of the limited weldability of the superalloy material constituting the part. Although the superalloy material melts easily, the region where the heat of fusion acts is prone to cracking during solidification, and reheat cracking is likely to occur due to the subsequent post-weld heat treatment necessary to reform the material properties.

  U.S. Pat. No. 7,169,242 shows a method for repairing small area forming defects in superalloy materials. Here, the repair is performed by redissolving the surface layer of material to a depth of 500 μm using a laser beam or other energy source in an inert atmosphere or under vacuum. It is described that a defect at a deep position can be repaired by preheating the member, and the risk of occurrence of a thermal fracture defect can be reduced.

  Since cracks after use are typically contaminated by the products of various combustion processes, weld repair is more difficult. Fluoride ion cleaning FIC that removes contaminants before welding can be used, but the effect is limited to narrow cracks, and it is likely that major elements will leach from the surrounding substrate material Can be extremely harmful when applied intensively.

  Welding methods vary significantly depending on the type of material being welded. While some materials can be welded relatively easily under various conditions, on the other hand, materials that require special treatment to achieve a structurally reliable bond without deteriorating the surrounding substrate There is also.

  Conventional arc welding generally uses a consumable electrode as the feed material. For example, when welding a wide variety of alloys, including steel, stainless steel and nickel-base alloys, an inert cover gas or flux material should be used to protect the molten material in the molten pool from the atmosphere. Can do. Gas tungsten arc welding GTAW (also known as tungsten inert gas TIG) and gas metal arc welding GMAW (metal inert gas) are used for inert gas processes and processes using both inert gas and active gas. (Mig; MIG), also known as the term metal active gas (Mag)). The processing method by flux protection includes submerged arc welding SAW for supplying flux in common, flux cored arc welding FCAW in which flux is contained in the core of the electrode, and flux is coated on the outside of the filler metal electrode. Shield metal arc welding SMAW is included.

  It is also known to use an energy beam as a heat source for welding. For example, laser energy has been used to weld pre-arranged stainless steel powder to a carbon steel substrate using a powdered flux material that provides a shield for the molten metal pool. The flux powder can be mixed with the stainless steel powder or can be applied as a separate cover layer. However, as far as the inventors of the present application know, flux materials have never been used when welding superalloy materials.

  Superalloy materials are recognized as belonging to materials that are most difficult to weld because they tend to cause weld solidification cracking and strain aging cracking. Here, the term “superalloy” is used in the meaning normally used in related fields. That is, it refers to an alloy having high corrosion resistance and oxidation resistance that exhibits excellent mechanical strength and creep resistance at high temperatures. Superalloys typically contain a high content of nickel or cobalt. Examples of superalloys include Hastelloy, Inconel alloys (eg, IN738, IN792, IN939), Rene alloys (eg, ReneN5, Rene80, Rene142), Highness alloys, Mar-M, CM247, CM247LC, C263, 718, X-750, Alloys sold under trademarks or trade names such as ECY768, 282, X45, PWA 1483 and CMSX (eg, CMSX-4) single crystal alloys are included.

  Weld repair of some superalloy materials preheats the superalloy material to very high temperatures (eg 1600 ° F or 870 ° C) to significantly increase the ductility of the superalloy material during repair. To be achieved. This technique is also referred to as “hot box welding” repair or “superalloy temperature-welded welding SWET” repair and is typically performed using a manual GTAW process. However, hot box welding is also extremely difficult due to the difficulty of maintaining a uniform part surface temperature and the difficulty of maintaining a complete inert gas shield. It is also limited by physical difficulties for operators working near hot parts.

  Among the uses of superalloy material welding, there is also an application performed using a chill plate in order to suppress heating of the base material. Thereby, the thermal influence of a base material arises and the problem of the crack resulting from a stress can be suppressed. However, this technique is not practical in many repair applications where the chill plate is difficult to use due to the geometric properties of the parts.

  FIG. 6 is a conventional diagram showing the relative weldability of various alloys depending on the aluminum content and titanium content of each alloy. Alloys such as Inconel (R) IN718, which have a relatively low gamma prime content due to the relatively low concentration of the two elements, generally, although the weld is limited to the low stress region of the part. It is considered to be relatively easy to weld. Alloys such as Inconel® IN939, which have a relatively high concentration of the two elements, generally do not have weldability or increase the temperature / ductility of the material and minimize the heat input of the process It is considered that welding cannot be performed without using the special procedure described above. For the sake of explanation, the broken line 80 represents the upper limit of the weldability region, and the region above the broken line 80 represents the non-weldability region. This broken line 80 intersects with the aluminum content of 3% by weight on the vertical axis and intersects with the titanium content of 6% by weight on the horizontal axis. In the non-weldable region, it is generally considered that the alloy with the highest aluminum content is the most difficult to weld.

  It is also known to use selective laser melting SLM or selective laser sintering SLS to weld a thin layer of superalloy powder particles to a superalloy substrate. The molten pool is shielded from the atmosphere by applying an inert gas such as argon during laser heating. These techniques facilitate the capture of oxides (eg, aluminum oxide or chromium oxide) adhering to the surface of the particles contained in the layer of deposited material, and are associated with the capture of the oxide such as pores, pores or other Cause defects. In many cases, the properties of the deposited coating are improved by eliminating such voids, pores and cracks by using a high-temperature isostatic press HIP after the treatment.

  Some superalloy materials in the non-weldable region are not known for welding and repair methods. Also, as new superalloys with higher alloy content continue to be developed, the challenge of developing commercially viable joining and repair processes for superalloy materials continues to increase.

  The present invention will be described below with reference to the drawings.

It is a figure which shows the clad formation process using multilayer powder. It is a figure which shows the clad formation process using mixed layer powder. It is a figure which shows the clad formation process using a flux cored welding wire and a low-temperature metal arc welding torch. It is a figure which shows the clad formation process using a flux-cored welding wire and an energy beam. It is a figure which shows the overlap pattern of an energy beam. It is a prior art figure which shows the relative weldability of various superalloys. It is a figure which shows the remelting repair process by the laser using a powdery flux material.

Detailed Description of the Invention For ease of reading, FIGS. 1-5 illustrate various aspects and applications of the technology of the present invention, and the following description of FIG. 7 is particularly within the scope of the claims. It should be noted that it is directed to the field of application of remelting repair of superalloy materials by laser of the present invention as listed.

  The inventors of the present application have developed a material joining process that can effectively join and / or repair superalloy materials that are very difficult to weld. Previously, flux materials have not been used in welding superalloy materials, but embodiments of the method of the present invention provide powdered flux materials on superalloy substrates during the melting and resolidification process. There is an advantage that can be applied. Further, in some embodiments, accurate energy input control means are used for energy beam heating processes, such as laser beam heating. Powdered flux material captures beam energy, cleans impurities, so that superalloy materials can be joined without cracking without the use of high temperature hot box welding or the use of chill plates or inert shielding gases. It is effective for carrying out air shielding, bead forming and cooling temperature control. The various components of the present invention have been known in the welding industry for decades, but the inventors of the present application have developed a superalloy material that eliminates cracks in superalloy materials that have long been a problem. We have achieved the innovation of developing a combination of multiple processes in the joining process.

  FIG. 1 shows a process of welding a superalloy material cladding layer 10 onto a superalloy substrate 12 at ambient temperature at room temperature without preheating the superalloy substrate 12 or using a chill plate at all. The substrate 12 can be part of a gas turbine engine blade, for example, and in some embodiments, the cladding formation process can be part of a repair process. A granular powder layer 14 is pre-arranged on the substrate 12, and the laser beam 16 is moved over the powder layer 14 to melt the powder, and the clad layer 10 covered with the slag layer 18 is formed. Form. The clad 10 and slag 18 are formed from a powder layer 14 that includes a layer of powdered superalloy material 20 covered with a layer of powdered flux material 22.

  The flux material 22 and the resulting slag layer 18 perform a number of advantageous functions to prevent cracking of the cladding layer 10 and the underlying substrate 12. First, the flux material 22 and the slag layer 18 shield both the molten material region and the solidified (but still hot) cladding material 10 region from the atmosphere in the direction of travel of the laser beam 16. It has a function. The slag migrates towards the surface and separates molten or hot metal from the atmosphere. In some embodiments, the flux can be formulated so that a shielding gas is generated, thereby avoiding or minimizing the use of high cost inert gases. Second, the slag 18 functions as a blanket to cool the solidified material slowly and evenly. By cooling in this way, it is possible to reduce residual stress that may cause reheat cracking or strain aging cracking after welding. Third, the slag 18 assists in shaping the molten metal pool so that the ratio of height to width of the pool is maintained near the desired 1: 3. Fourth, the flux material 22 realizes a cleaning action for removing trace impurities such as sulfur and phosphorus that cause weld solidification cracking. This cleaning involves deoxidation of the metal powder. Since the flux powder is in close contact with the metal powder, it is particularly effective for realizing the above functions. Finally, the flux material 22 enhances the efficiency of the conversion of the laser beam 16 into thermal energy by realizing the energy absorption and collection function, thereby enabling accurate heat input within 1-2%, for example. And precise control of the material temperature during processing can be facilitated. Furthermore, the flux can also be formulated so that the loss of elements volatilized during processing is compensated, or so that components that are not realized with the metal powder itself are positively imparted to the deposit. Overall, these treatment steps form a superalloy-cladding-free weld on a superalloy substrate at room temperature for materials that were previously thought to be bonded only using a hotbox process or chill plate. it can.

  FIG. 2 shows another embodiment in which a superalloy material cladding layer 30 is welded onto a superalloy substrate 32. In this embodiment, the superalloy substrate 32 is shown as a directionally solidified material having a plurality of columnar crystal grains 34. In this embodiment, the powder layer 36 is pre-positioned or supplied on the surface of the substrate 32 as a homogeneous layer comprising a mixture of both powdered alloy material 38 and powdered flux material 40. To do. In some embodiments, the thickness of the powder layer 36 is between 1 mm and several mm, rather than less than 1 mm typical in known selective laser melting and selective laser sintering processes. be able to. The particle size of typical powdered flux material of the prior art is, for example, in the range of 0.5 mm to 2 mm. However, the particle size range (mesh size range) of the powdered alloy material 38 is 0.02 mm to 0.04 mm, or 0.02 mm to 0.08 mm, or a part of this range. can do. Although the mesh size range is different, the embodiment of FIG. 1 in which each material constitutes a separate layer works well, but in the embodiment of FIG. To facilitate, and further to improve the coverage by the flux during the melting process, the mesh size range of the powdered alloy material 38 and the mesh size range of the powdered flux material 40 may overlap or be the same. It is advantageous.

  The energy beam 42 in the embodiment of FIG. 2 is a diode laser beam having a generally square cross-sectional shape, but other known types of energy beams can be used, such as an electron beam, a plasma beam, It is also possible to use one or more circular laser beams, scanning laser beams (one-dimensional scanning or two-dimensional scanning or three-dimensional scanning), integrated laser beams and the like. The square shape is particularly advantageous for embodiments where the cladding coverage is a relatively large area, such as for repairing the tip of a gas turbine engine blade. Such wide area beams produced by diode lasers help reduce welding heat input, heat affected zone, substrate dilution and residual stress, all of which are usually associated with superalloy repair. Reduces the tendency to cause cracking.

The optical conditions and optical system equipment used to realize laser exposure over a wide area are:
-Defocus distance of the laser beam;
The use of a diode laser that generates a square energy source at the focal point;
The use of integrated optics such as segment mirrors that generate a square energy source at the focal point;
・ Scanning of the laser beam in one dimension or more (raster scanning);
A collection of variable beam diameters (for example, when performing fine machining operations, the focal beam diameter is 0.5 mm, and when performing relatively non-fine operations, the focal beam diameter reaches 2.0 mm). Use of optical optics;
It is possible to include, but is not limited to these. To form a custom shaped weld layer, the movement of the optics and / or substrate can be programmed in the same manner as the selective laser melting process or the selective laser sintering process. Advantages of the known laser melting method and laser sintering method that are achieved by the above-described process include:
-The welding speed is fast and the welding thickness in each treatment layer is thick;
The shield has been improved to cover the entire hot weld metal without the need to use an inert gas;
-Flux enhances the cleaning of welded components that cause solidification cracking;
The flux increases laser beam absorption and minimizes reflections back to the processing equipment;
-The welded material is formed and supported by slag formation, the heat is stored, and the cooling rate is slowed, thereby reducing the residual stress that causes strain aging (reheating) cracking during post-weld heat treatment;
・ The component loss is compensated by the flux or the alloy component is added and the welded material is thick, so the total time required for the entire part formation is greatly shortened. What you can do selectively;
Etc. are included.

  The embodiment of FIG. 2 also illustrates the use of a base alloy feed material 44 (also optionally referred to as a filler metal). The feed material 44 may be in the form of a wire or strip that is fed or vibrated in a direction toward the substrate 32 and melted by the energy beam 42 to become part of the molten pool. If desired, the feed material can be preheated (eg, electrically) to reduce the total energy to be obtained from the laser beam. Some superalloy materials are difficult or impossible to mold into wire or strip shapes, but materials such as pure nickel or nickel chrome or nickel chrome cobalt are readily available in these shapes . In the embodiment of FIG. 2, the base alloy feed material 44 and the powdered alloy material 38 and the powdered flux material 40 are preferably selected such that the cladding material layer 30 has the desired superalloy material composition. . The filler material can only be an extrudable element subset of the elemental composition that determines the desired superalloy material, and the powdered metal material supplements the elements in the filler material, Components are included that complete the elemental composition that determines the desired superalloy material. The filler metal and the powdered metal material are combined in the melt pool to form the desired superalloy material 30 repair surface. As shown in FIG. 1, the treatment produces a slag layer 46 that protects, molds, and thermally insulates the cladding-forming material layer 30.

  FIG. 3 shows an embodiment in which a superalloy material layer 50 is deposited on a superalloy substrate 52 using a low temperature metal arc welding torch 54. The torch 54 is used to supply and melt a filler material 56 in the form of a flux-cored wire material or strip material including a hollow metal sheath 57 filled with a powdered core material 59. The powdered core material 59 can include a powdered metal alloy and / or a flux material. Preferably, the metal sheath 57 is made of a material that can be easily formed into a hollow shape, such as nickel or nickel chrome or nickel chrome cobalt, and the powdered core material 59 is formed when the filler material 56 is melted. It is selected to form the desired superalloy composition. For example, the sheath contains a sufficient amount of nickel (or cobalt) to achieve the desired superalloy composition so that the solid to solid ratio of the sheath to powdered fluxed material can be maintained at a ratio of 3: 2. The heat of the arc melts the filler material 56 to form the desired superalloy material layer 50 covered by the slag layer 58. The powdery flux material is contained in the filler material 56 (for example, 25% of the core volume), or the powdery flux material is previously disposed on the surface of the substrate 52 or the surface of the substrate 52 It can be formed by welding on top (not shown in FIG. 3; see FIG. 2), or by coating the electrode with a flux material, or any combination thereof. The powder metal material to be supplemented is added to the molten pool by prepositioning on the surface of the substrate 52 or by feeding directly to the molten pool during the melting step (not shown in FIG. 3). See FIGS. 1 and 2). In various embodiments, the flux can be conductive (electroslag) or non-conductive (submerged arc), and the flux can be chemically neutral or additive. As described above, in order to reduce the required processing energy, in this embodiment, the filler material can be preheated in order to reduce the processing energy to be obtained from the low temperature metal arc torch. By using flux, shielding is achieved, which can reduce or eliminate the need to use inert or partially inert gases that are normally required in low temperature metal arc processes. .

  In the embodiment shown in FIG. 4, the superalloy material layer 60 is welded onto the superalloy substrate 62 using an energy beam such as a laser beam 64 in order to melt the filler material 66. As described above with reference to FIG. 3, the filler material 66 has a metal sheath 68 made of a material that can be easily formed into a hollow shape, such as nickel, nickel chrome, or nickel chrome cobalt. The powder material 70 is selected so that a desired superalloy composition is formed when the filler material 66 is melted by the laser beam 64. The powdered material 70 can include both powdered flux and alloy components. The heat of the laser beam 64 melts the filler material 66 to form the desired superalloy material layer 60 covered by the slag layer 72. As described above, in order to reduce the required processing energy, in this embodiment, in order to reduce the processing energy to be obtained from the laser beam, the filler material can be preheated, for example, with an electric current.

One embodiment of filler material 56, 66 is formulated to weld alloy 247 material as follows:
The sheath solid volume is about 60% of the total metal solid volume and is pure Ni;
The core metal powder volume is approximately 40% of the total metal solid volume, and when dissolved or mixed with pure nickel from the sheath, nominally 8.3% Cr, 10% Co, 0% 0.7 wt% Mo, 10 wt% W, 5.5 wt% Al, 1 wt% Ti, 3 wt% Ta, 0.14 wt% C, 0.015 Sufficient Cr, Co, Mo, W, Al, Ti, Ta, C to produce an alloy 247 having a composition of wt% B, 0.05 wt% Zr, and 1.5 wt% Hf. , B, Zr and Hf;
The core flux powder volume is an additional wire volume that is mostly non-metallic and contains alumina, fluoride and silicate in a ratio of 35:30:35. The size of the wire volume can in some cases be equal to the size of the metal powder volume. The mesh size range of the flux is uniformly distributed in the core metal powder.

  In embodiments where the heat of fusion is generated by an arc, it is common to include oxygen or carbon dioxide in the flux or shielding gas to maintain arc stability. However, during the melting process, oxygen or carbon dioxide reacts with titanium and a part of titanium is lost as vapor or oxide. In order to compensate for the above-described loss of titanium by this method, the amount of titanium contained in the filler material can be made larger than the desired amount of titanium in the superalloy composition after welding. For example, in the case of the alloy 247 described above, the amount of titanium contained in the core metal powder can be increased from 1% to 3%.

  It should be readily appreciated by those skilled in the art that other alloys, such as stainless steel, can be deposited in a similar process in which a powdered core material including powdered flux and powdered metal is added to the core feed. . Powdered metal is used to increase the composition of the sheath material to obtain a cladding material having the desired chemical properties. In embodiments where loss of material occurs due to volatilization during the melting step, the powdered metal contains more material that is lost to compensate for the loss. For example, if an alloy 321 stainless steel sheath material is deposited in a shielding gas containing oxygen or carbon dioxide, some of the titanium from the sheath material is lost by reaction with oxygen or carbon dioxide. The powdered core material in these embodiments can include powdered flux and powdered titanium to compensate for the loss, so that the desired alloy 321 cladding composition can be achieved.

  The repair process for superalloy materials prepares the surface of the superalloy material to be repaired by polishing or surface cleaning as desired to remove defects and pre-positions a powdered material layer containing flux material on the surface Or supplying and then moving the energy beam across the surface to melt the powder and the upper layer of the surface to form a floating molten pool of slag layer, and then solidify the molten pool and slag. .

  Melting typically has the function of healing any substrate defects on the surface of the substrate to make the surface repaired by removing the slag, typically by known mechanical and / or chemical treatments. The powdered material may be a flux material only, or in the case of an embodiment where a superalloy cladding material layer is desired, the powdered material is a metal so that the cladding layer is formed on the surface by melting Powders may be included. Here, the metal powder is a separate layer disposed below the powdery flux material layer, or is mixed with the powdery flux material or combined with the flux material to form composite particles. Can do. Optionally, the feed material can be introduced into the melt pool in the form of strips or wires. Powdered metal material and feed material (if they are used) and any neutral or additive metal contribution from the flux material are combined in the molten pool to achieve the desired superalloy material composition. A clad layer is produced. In some embodiments, nickel, nickel chromium, nickel chromium cobalt, or other metal feeds that are extruded are combined with a suitable alloy metal powder to achieve the desired superalloy composition in the cladding. . This avoids the problem of forming the desired superalloy material into the shape of a wire or strip.

  Preheating the substrate is not always necessary to obtain an acceptable product, but for example to increase the ductility of the substrate and / or the beam energy required to melt the filler material. In some embodiments, it may be desirable to apply heat to the superalloy substrate and / or feedstock and / or powder prior to the melting step. The improvement in ductility of some superalloy substrates is achieved at temperatures above about 80% of the melting point of the alloy. In certain applications, a chill fixture can also be used as an option. As a result, combined with the high-precision heat input of the energy beam, the stress generated in the material as a result of the melting process can be minimized. The method described above can further eliminate the need to use an inert shielding gas. However, auxiliary shield gas may be used in some applications where appropriate. When the filler material 44 is used, in some embodiments, the filler material 44 can be preheated.

  Flux materials that can be used include commercially available fluxes sold under the trade name Lincoln Weld P2007, BohlerSoudokay NiCrW-412, ESABOK 10.16 or 10.90, Special Metal NT100, Erlikon OP76, Sandvik 50SW or SAS1. By grinding the flux particles prior to use, a smaller desired mesh size range can be achieved. Flux materials known in the art typically include alumina, fluoride, silicates, and the like. Advantageous embodiments of the method described above include the metal component of the desired cladding material, such as chromium oxide or nickel oxide or titanium oxide. Bonding, repairing or coating any of the presently available iron, nickel-based or cobalt-based superalloys commonly used for high temperature applications such as gas turbine engines, including the above alloys, by the process of the present invention. Can do.

  In other variations, heat for melting can be generated through the feed material instead of or in combination with the energy beam. For example, by energizing the wire or strip of feed material 44 of FIG. 2, an arc can be generated below the powder and flux layers. In that case, the wire should be a readily available material in an extruded form (ie, a material that is not a superalloy material) and the powder must have the desired superalloy composition in the combined molten pool. It contains other alloy components necessary for the production. Alternatively, for example, conductive powders and fluxes can be selected to facilitate an electroslag welding process that is effective in forming a superalloy cladding material layer. In yet another embodiment, a conventional plasma arc cladding forming apparatus can be used to supply a mixture of flux powder and superalloy powder material to the superalloy substrate. In that case, a chill fixture can be used as an option. In various embodiments, the substrate, feed material and / or powder can be preheated. Since the accuracy of heat input is higher when using an energy beam (± 10 to 15%) than when using an electrode (± 1 to 2%), the amount of heat input exceeding half of the total heat input is It is preferred to use an energy beam. Depending on the energy of the beam, submerged arc treatment or electroslag treatment can result in a preliminary melt pool with minimal dilution from the substrate, which can then have a greater impact on the substrate. Instead, a submerged arc or electroslag contribution is added to the deposit volume, which can minimize the dilution effect.

  In various embodiments, a mixture of submerged arc welding flux and alloy 247 powder was pre-positioned at a depth from 2.5 mm to 5.5 mm. Then, after performing the final post-weld heat treatment, it was possible to realize laser clad welding without cracking with the mixture. By using an ytterbium fiber laser having an output level of 0.6 kW to a maximum of 2 kW and a galvanometer scanning optical system, a weld having a width of 3 mm to 10 mm was formed at a traveling speed of the order of 125 mm / min. It was confirmed that there was no crack by subjecting the cross section of the welded material to a dye penetration test and a metal structure inspection. As shown in FIG. 6, the alloy 247 belongs to the most difficult-to-weld alloy among the known superalloys. Therefore, the entire range of superalloys including aluminum superalloys exceeding 3% by weight is included. It can be said that the composition has shown that the present invention is operable.

  It has been recognized that the advantage of using a powdered flux material in repairing a superalloy substrate is that any additive cladding material is deposited anyway. The surface crack of the superalloy substrate can be repaired by covering the surface with a powdery flux material and then heating the surface and the flux material to form a molten metal pool with a slag layer floating thereon. By solidifying the molten pool while protecting with a slag layer, a surface free of cracks and contaminants is formed.

  In general, by using a diode laser having a square energy density, the laser energy can be applied to the entire surface. Instead, a planar energy distribution can be generated by performing a raster scan by reciprocating a circular laser beam along the substrate. FIG. 5 shows a raster scan pattern of one embodiment, wherein the raster scan pattern passes a generally circular beam having a focal diameter D from a first position 74 through a second position 74 ′. In order to achieve the optimum heating and melting of the material, it is advantageous to realize the amount of overlap O of the beam diameter pattern at the direction change position. Is between 25 and 90% of the diameter D. Alternatively, two energy beams can be raster scanned simultaneously to achieve the desired energy distribution across the surface. The overlap of each beam pattern is set within a range of 25 to 90% of the diameter of each beam.

  By using a powdery material, it becomes easy to weld a functional material whose composition of the material to be welded changes temporally and spatially. For example, the alloy composition can be changed from the inner wall to the outer wall of the product or from the inside of the product to the vicinity of the surface. Depending on the assumed operating conditions, which differ in the required mechanical and corrosion resistance properties, and in consideration of material costs, the synthetic composition can also be varied.

  FIG. 7 illustrates a process for repairing defects near the surface, such as cracks after use of a superalloy surface of a gas turbine hot gas path component. A substrate 90 having one or more cracks 92 near the surface is conveyed relative to the repair device 96 in the direction of arrow 94. An energy beam, such as a laser beam 98, is directed by a repair device 96 to a powder layer 100 containing a powdery flux, and the powdery flux is delivered to the surface via a nozzle 102 or optionally on a substrate 90. Pre-positioned. The laser beam 98 melts the powder 100 and the thin surface area of the substrate 90 to form a redissolved area 104 covered by the slag layer 106 on the substrate 90. As the remelted region 104 moves away from the laser beam 98, it resolidifies below the slag 106 to form a repaired, crack-free surface 108. The powdery flux 100 prevents the high-temperature material melted and stretched from reacting with air without using an inert cover gas. That is, the flux is coupled to the laser and thermal energy to trap it and ensure that dissolution occurs to a sufficient depth of the substrate 90 so that the surface crack 92 is repaired.

  The process of FIG. 7 advantageously provides a mechanism for cleaning and deoxidizing the molten pool, where contaminants present in the crack 92 react with the contaminants and become one of the slugs 106. By migrating to the surface forming the part, it is removed without the need for pre-weld fluoride ion cleaning. The surface of the substrate 90 is cleaned, such as by a wire brush or grit blasting process, to remove the upper ceramic thermal barrier coating or contaminants attached to the surface prior to the remelting process. However, the superficial crack cleaning process such as fluoride ion cleaning is optional and can be avoided in other embodiments. This process allows the repair of cracks caused by use of superalloy materials having a composition that exceeds the line 80 in the non-weldable region of FIG. 6 without the need for preheating or reheat cracking after melting. While not necessarily essential to obtain acceptable results during substrate preheating, in some embodiments to increase the ductility of the substrate and / or to reduce the required beam energy, It is desirable to apply heat to the superalloy substrate and / or powder prior to the melting step.

The powder 100 of the process of FIG. 7 may additionally be supplied as a filler material with the flux pre-mixed and supplied together or separately supplied or pre-positioned to the remelt zone. A powdered alloy material may be included. Alternatively, the filler material may be supplied as the wire material or strip material shown in FIG. Such a filler material may have the same composition as the substrate 90 or may have a different composition, eg, to provide some different properties to the remelted region 104. As mentioned above, the flux and filler powder have the same or overlapping mesh size range. Various types of lasers (CO ₂ , NdYAG, fiber, diode, etc.) are used together with various types of optical systems (focusing optical system, defocusing optical system, integrated beam optical system, scanning beam optical system, etc.) it can.

  While various embodiments of the invention have been illustrated and described, it will be appreciated that these embodiments are merely exemplary and that many variations, modifications, and substitutions can be made without departing from the invention. Accordingly, the invention is limited only by the following claims.

Claims (19)

Applying a powdery flux material to the surface of the superalloy substrate containing the defects;
Moving an energy beam across the surface to form a remelting region on the substrate, over which a slag layer covers;
Solidifying the remelted region below the slag layer to form a defect free repair surface;
Including methods. The energy beam is a laser beam;
The method of claim 1. During the step of moving the energy beam across the surface, the method further comprises applying a filler material to the surface and adding a molten filler material to the remelt region.
The method of claim 1. Further comprising applying the filler material to the surface as a powdered alloy material.
The method of claim 3. The mesh size range of the powdered alloy material overlaps the mesh size range of the powdered flux material,
The method of claim 4. Further comprising applying the filler material as a wire material or a strip material.
The method of claim 3. The superalloy substrate has a composition that exceeds the weldability region defined in the superalloy graph representing titanium content versus aluminum content;
The upper limit of the weldability region is defined by a line that intersects the titanium content axis at 6% by weight and intersects the aluminum content axis at 3% by weight.
The method of claim 1. Applying heat to the substrate prior to moving the energy beam across the surface;
The method of claim 1. Covering the substrate with a powdered flux material;
Melting the powdery flux material and the surface area of the substrate with an energy beam to form a remelted area of the substrate below the slag layer;
Cooling and solidifying the remelted region below the slag layer;
Removing the slag;
Heat-treating the substrate without causing reheat cracking, and
The base material has a composition exceeding the weldability region defined in the superalloy graph representing the titanium content to the aluminum content, and the upper limit of the weldability region is 6 wt. % And defined by a line intersecting the aluminum content axis at 3% by weight,
Method. The energy beam is a laser beam;
The method of claim 9. Further comprising melting a filler material with the energy beam and adding the melted filler material to the remelt region.
The method of claim 9. Further comprising applying the filler material as a powdered alloy material.
The method of claim 11. The mesh size range of the powdered alloy material overlaps the mesh size range of the powdered flux material,
The method of claim 12. Further comprising applying the filler material as a wire material or a strip material,
The method of claim 11. Further comprising applying heat to the substrate prior to the dissolving step;
The method of claim 9. Removing a superalloy hot gas path component from the point of use in the gas turbine engine;
Applying a flux material to the surface of the part containing defects;
Melting the surface of the component and the flux material with an energy beam to form a remelt layer below the slag layer;
Cooling the remelted layer below the slag;
Removing the slag to expose a defect-free repair surface of the part. Performing the dissolving step without previously performing the step of cleaning superficial cracks;
The method of claim 16. The base material has a composition exceeding the weldability region defined in the superalloy graph representing the titanium content to the aluminum content, and the upper limit of the weldability region is 6 wt. % And defined by a line intersecting with the aluminum content axis at 3% by weight,
After the step of removing the slag, further comprising the step of heat treating the part without causing reheat cracking;
The method of claim 16. Further comprising applying heat to the surface of the part prior to the melting step;
The method of claim 16.

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