Welding repair method for high-aluminum titanium cast high-temperature alloy

Abstract

The invention relates to the technical field of aero-engine maintenance, in particular to a high-aluminum-titanium cast high-temperature alloy welding repair method which aims at solving the problems that the aluminum-titanium content is larger than or equal to 9%, gamma phase enhanced cast high-temperature alloy is poor in welding performance, and the welding repair qualification rate is low due to the fact that hot cracks are likely to be generated. Firstly, a bench worker is used for polishing a U-shaped groove to remove cracks, then a low-aluminum-titanium layer is formed on the surface of a to-be-welded area through a pulse high-activity high-temperature bond separation reaction technology so as to improve weldability of a part, then a low-heat-input TIG welding technology is adopted for surfacing repair, the one-time welding qualification rate can reach 75% or above, the room-temperature strength of a weld joint reaches 95% or above of a base material, and the welding quality is improved. The high-temperature tensile strength reaches more than 60% of that of a base material, the fatigue strength is high, and the method has the advantages of simplicity and convenience in operation, no need of special preheating and slow cooling, high efficiency, low cost and the like, is suitable for various workpieces with complex structures, and is easy to realize batch processing.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft engine maintenance, and in particular to a welding repair method for a high-aluminum-titanium cast high-temperature alloy. Background Art

[0002] High-temperature alloys have high strength, creep resistance and fatigue resistance at high temperatures, and have good oxidation and corrosion resistance and organizational stability. They are mainly used to manufacture aircraft engines, rocket engines and gas turbine hot end components. In modern aircraft engines, the amount of high-temperature alloy materials accounts for 40% to 60% of the engine weight.

[0003] Without high-temperature alloys, there would be no high-speed, high-efficiency, safe and reliable modern aviation industry. The good high-temperature performance of high-temperature alloys mainly comes from the precipitation strengthening effect of aluminum and titanium elements and the protective effect of aluminum and titanium elements on the matrix by forming a stable and dense oxide film at high temperature. With the increase of aluminum and titanium content, the melting point of high-temperature alloy materials increases, the thermal expansion coefficient increases, and the thermal conductivity decreases. Aluminum and titanium elements are prone to oxidation during the melting process, which makes welding more difficult, and it is very easy to produce cracks and pores. The qualified rate of traditional fusion welding is very low. Usually, high-temperature brazing, such as vacuum brazing, is used for repair, but the high-temperature fatigue strength of the brazed seam is low, and it is difficult to ensure long-term reliable use in a high-temperature thermal cycle environment.

[0004] A Chinese patent with publication number CN117203009A discloses a method for welding gamma-enhanced high-temperature alloys and other easily cracked materials. The method adopts a stacking form of welding beads and layered stacking. The welding heat input can be reduced without preheating, thereby reducing welding cracks. However, the operation process is very complicated, requiring a large number of balls, and the performance of the surfacing layer is very different from that of the substrate.

[0005] The Chinese patent with publication number CN102218618A discloses a high-aluminum-titanium nickel-based high-temperature alloy surfacing equipment and method, including a protective gas hood, a welding gun, and a welding power supply, wherein an induction coil is arranged around the protective gas hood to heat the workpiece in the protective hood by induction; the welding gun is connected to the welding power supply to perform plasma welding surfacing on the workpiece, and the protective gas flows from top to bottom in the protective hood to provide inert atmosphere protection for the workpiece. This method uses an auxiliary induction preheating method, the processing efficiency is low, and the induction coil is limited by the workpiece structure, and is only applicable to workpieces with simple structures.

[0006] In order to solve the fundamental problem that high aluminum and titanium content leads to poor weldability of parts, the present invention adopts high-temperature chemical reaction to consume aluminum and titanium elements in the shallow surface layer of parts to improve the weldability of parts, thereby fundamentally solving the problem of difficult welding of parts. Summary of the invention

[0007] In view of the above problems, the present invention provides a welding repair method for high-aluminum-titanium cast high-temperature alloy.

[0008] The technical solution adopted is a high-aluminum-titanium cast high-temperature alloy welding repair method, comprising the following steps: S1. Open a U-shaped groove on the substrate before welding; S2. Performing a high temperature chemical reaction on the substrate after the U-shaped groove is opened; S3. TIG welding is performed on the substrate after high temperature chemical reaction; S4.Relieve stress after welding; S5. Nondestructive testing.

[0009] Furthermore, in S1, the opening width of the U-shaped groove is 3 mm to 5 mm, the bottom width is half of the opening width, and the groove depth is ≤6 mm.

[0010] Furthermore, in S2, the high temperature chemical reaction is a pulse high activity high temperature bond separation chemical reaction, the reaction temperature is 900°C to 1000°C, the high activity reaction gas introduced is a mixed gas of hydrogen and hydrogen fluoride, and the pressure variation range is 100Mbar to 2000Mbar.

[0011] Furthermore, in S2, the content of hydrogen fluoride in the mixed gas of hydrogen and hydrogen fluoride is 5% to 30%.

[0012] Furthermore, in S3, the U-shaped groove is welded in multiple passes, wherein the maximum weld thickness of each single pass is ≤3 mm.

[0013] Furthermore, in S3, the welding wire model selected for cladding is HGH625 or HGH3128.

[0014] Furthermore, in S4, the temperature is kept at 750°C to 770°C for 2h to 2.5h.

[0015] Furthermore, in S5, a penetration inspection and an X-ray fluoroscopic inspection are performed on the repair welding area.

[0016] Furthermore, before the U-shaped groove is opened before welding the substrate, the substrate is inspected by fluorescence and the cracks are marked.

[0017] The beneficial effects of the present invention are: 1. Provide a high-aluminum-titanium cast high-temperature alloy welding repair method, which is a combination of high-temperature chemical reaction and argon arc welding process. The technical solution is to use the method of groove grinding to eliminate cracks and other defects in the cast high-temperature alloy material, remove the oxide on the surface of the matrix and reduce the aluminum-titanium content in the shallow surface layer through high-temperature chemical reaction, and then use a multi-pass argon arc welding method to repair the workpiece; 2. For the repair of cast high-temperature alloys with Al-Ti content ≥9% and gamma phase enhancement, the one-time repair pass rate is over 75% and the welding crack rate is low.

[0018] 3. The pulse high-activity high-temperature bond separation reaction has a large furnace capacity, groove grinding and TIG welding are easy to operate, the repair efficiency is high, and batch repairs are easy to achieve.

[0019] 4. The selected welding wire has excellent welding performance. The room temperature tensile strength of the weld is equivalent to that of the base material. The high temperature tensile strength of 700℃ reaches more than 60% of the base material. It is also suitable for workpieces with complex structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a real picture of welding repair of a high-aluminum-titanium cast high-temperature alloy. DETAILED DESCRIPTION

[0021] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0022] It should be noted that the illustrations provided in the following embodiments are only used to schematically illustrate the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0023] In this embodiment, a high-aluminum-titanium cast high-temperature alloy welding repair method is provided, comprising the following steps: S1. Open a U-shaped groove on the substrate before welding; S2. Performing a high temperature chemical reaction on the substrate after the U-shaped groove is opened; S3. TIG welding is performed on the substrate after high temperature chemical reaction; S4.Relieve stress after welding; S5. Nondestructive testing.

[0024] The purpose of this design is that step S1 can remove the oxide film or other defects inside the matrix crack, while step S2 can remove the oxide on the matrix surface and reduce the aluminum-titanium content in the shallow surface layer of the surface to be welded. Step S3 can reduce the penetration depth of the base material, and step S4 can remove the welding stress according to the standard heat treatment system of the material. Finally, step S5 performs penetration inspection and X-ray fluoroscopy on the repair welding area to meet the weld acceptance standards.

[0025] Meanwhile, in a specific implementation, in S1, the opening width of the U-shaped groove is 3 mm to 5 mm, the bottom width is half of the opening width, and the groove depth is ≤6 mm.

[0026] Furthermore, in S2, the high-temperature chemical reaction is a pulse high-activity high-temperature bond-separation chemical reaction, the reaction temperature is 900°C to 1000°C, the high-activity reaction gas introduced is a mixed gas of hydrogen and hydrogen fluoride, and the pressure variation range is 100Mbar to 2000Mbar.

[0027] Meanwhile, in S2, the content of hydrogen fluoride in the mixed gas of hydrogen and hydrogen fluoride is between 5% and 30%.

[0028] Furthermore, in S3, the U-shaped groove is welded in multiple passes, wherein the maximum weld thickness of each single pass is ≤3 mm.

[0029] At the same time, in S3, the welding wire model selected for cladding is HGH625 or HGH3128.

[0030] Furthermore, in S4, the temperature is kept at 750°C to 770°C for 2h to 2.5h.

[0031] At the same time, in S5, the repair welding area is subjected to a penetration inspection and an X-ray fluoroscopic inspection.

[0032] Finally, before the U-shaped groove is opened before welding the substrate, the substrate is inspected by fluorescence and the cracks are marked.

[0033] The purpose of this design is to provide a high-aluminum-titanium cast high-temperature alloy welding repair method, which is composed of a combination of high-temperature chemical reaction and argon arc welding process. The technical solution is to use the method of groove grinding to eliminate cracks and other defects in cast high-temperature alloy materials, remove the surface oxides of the substrate and reduce the aluminum-titanium content of the shallow surface layer through high-temperature chemical reaction, and then repair the workpiece through a multi-pass argon arc welding surfacing method; for the repair of cast high-temperature alloys with aluminum-titanium content ≥9% and gamma phase enhancement, the one-time repair pass rate is more than 75%, and the welding crack rate is low. The pulse high-activity high-temperature bond separation reaction has a large furnace loading capacity, groove grinding and TIG welding surfacing are simple to operate, the repair efficiency is high, and batch repair is easy to achieve. The selected welding wire has excellent welding performance, the room temperature tensile strength of the weld is equivalent to that of the substrate, and the high-temperature tensile strength at 700℃ reaches more than 60% of the substrate. It is also suitable for workpieces with complex structures.

[0034] In this embodiment, a regulating plate used for the tail nozzle of an aircraft engine was repaired after service and found to have thermal fatigue crack failure, with a crack rate exceeding 50%. Figure 1 As shown, due to the stress concentration in the structure, the cracks are mainly concentrated at the corners R on both sides (where the arrows point to), requiring the weld to have high strength. The adjustment plate is K424 high aluminum-titanium low-density nickel-based cast high-temperature alloy with an aluminum-titanium content of 9.2% to 10.4%. The technical solution consists of the following: S1. Fluorescent flaw detection inspection, marking cracks and other faults; S2. Open a U-shaped groove before welding to remove the oxide film or other defects inside the matrix crack. The groove opening width is 3mm~4mm, the bottom width is 1.5mm~2mm, and the groove depth is to eliminate the defects. If the maximum depth exceeds 6mm and the defects are not eliminated, no repair is done; S3. Pulse high-activity high-temperature bond separation reaction to remove oxides on the substrate surface and shallow aluminum and titanium elements on the surface of the welded part. The maximum furnace load is 80 pieces, the reaction temperature is 950℃±10℃, the hydrogen fluoride input accounts for 20%±5%, and the pressure in the furnace varies from 100Mbar to 2000Mbar. S4. Argon arc welding, multiple passes to complete the cladding of the U-shaped groove, the maximum thickness of a single pass cladding layer ≤ 3mm, use HGH625 welding wire, and argon gas protection on both sides of the weld; S5. Remove stress after welding and keep at 760℃±10℃ for 2h~2.5h; S6. Non-destructive testing: Fluorescent inspection and X-ray inspection of the repaired welding area are required. Cracks and pores with a diameter exceeding 0.3mm are not allowed.

[0035] The qualified rate of the regulating piece welded repaired in one time using the above method is 78%, and the repaired regulating piece can be used for a long time in a high-temperature gas environment of 750℃.

[0036] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A welding repair method for high-aluminum-titanium cast high-temperature alloy, characterized in that: The following steps are involved: S1. Open a U-shaped groove on the substrate before welding; S2. Performing a high temperature chemical reaction on the substrate after the U-shaped groove is opened; S3. TIG welding is performed on the substrate after high temperature chemical reaction; S4.Relieve stress after welding; S5. Nondestructive testing.

2. A high-aluminum-titanium cast high-temperature alloy welding repair method according to claim 1, characterized in that: In S1, the U-shaped groove opening width is 3 mm to 5 mm, the bottom width is half of the opening width, and the groove depth is ≤6 mm.

3. The high aluminum titanium cast high temperature alloy welding repair method according to claim 1, characterized in that: In S2, the high-temperature chemical reaction is a pulse high-activity high-temperature bond-separation chemical reaction, the reaction temperature is 900°C to 1000°C, the high-activity reaction gas introduced is a mixed gas of hydrogen and hydrogen fluoride, and the pressure variation range is 100Mbar to 2000Mbar.

4. A high-aluminum-titanium cast high-temperature alloy welding repair method according to claim 3, characterized in that: In S2, the content of hydrogen fluoride in the mixed gas of hydrogen and hydrogen fluoride is 5% to 30%.

5. The high aluminum titanium cast high temperature alloy welding repair method according to claim 1, characterized in that: In S3, the U-shaped groove is welded in multiple passes, wherein the maximum weld thickness of each single pass is ≤3 mm.

6. A high-aluminum-titanium cast high-temperature alloy welding repair method according to claim 5, characterized in that: In S3, the welding wire model selected for cladding is HGH625 or HGH3128.

7. The high aluminum titanium cast high temperature alloy welding repair method according to claim 1, characterized in that: In S4, the temperature is kept at 750°C to 770°C for 2h to 2.5h.

8. The high aluminum titanium cast high temperature alloy welding repair method according to claim 1, characterized in that: In S5, the repair welding area is subjected to a penetration inspection and an X-ray fluoroscopic inspection.

9. A welding repair method for high-aluminum-titanium cast high-temperature alloy according to any one of claims 1 to 8, characterized in that: Before the U-shaped groove is opened before welding the substrate, the substrate is inspected by fluorescence and the cracks are marked.

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