High-strength fusion welding repair method for gas turbine hot end component difficult to weld

Abstract

The invention belongs to the field of repair of high-temperature alloy hot-end components, and particularly relates to a high-strength fusion welding repair method for a difficult-to-weld gas turbine hot-end component. The method comprises the following steps: (1) removing defects of the hot end component of the gas turbine; (2) degreasing the repairing area; (3) carrying out fusion welding repair on the defects by adopting a body welding wire; (4) a surfacing sheath is prepared on the outer surface of the repaired area through solution-strengthened nickel-based alloy welding filler; (5) carrying out hot isostatic pressing treatment on the hot end component; (6) machining and coping a repair area of the hot end component; (7) carrying out nondestructive flaw detection on a hot end component repair area; (8) carrying out standard heat treatment on the hot-end component; and (9) carrying out nondestructive inspection on the hot-end component. The method is used for fusion welding repair of casting defects of the high-temperature alloy hot-end component with high Al + Ti content and difficult to weld and service damage generated after service of the blade, and crack-free high-strength fusion welding repair of the gas turbine hot-end component with poor weldability can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of repair of hot-end components of superalloys, and particularly relates to a high-strength fusion welding repair method for difficult-to-weld hot-end components of gas turbines. This method is used for high-strength fusion welding repair of casting defects and service-induced damages generated after the service of hot-end components of difficult-to-weld superalloys with high Al + Ti content. Background Art

[0002] Gas turbines have the advantages of high efficiency, low pollution, compact structure, fast startup, high reliability, etc., and are widely used in the fields of self-generated power, ship power, and mechanical drive. At present, the turbine blades of aeroengines are mainly precipitation-strengthened cast nickel-based superalloys, which are produced by vacuum precision investment casting process. Due to the complex casting process and many processes, some surface porosity and slag inclusion defects are often found during the subsequent fluorescent inspection of the blades after casting. If these defects are located in the non-critical areas of the blades, welding repair means can be used for repair; in addition, after the blades are cast, extremely complex processes such as machining, inspection, non-destructive testing, and protective coating preparation are also required, and the manufacturing cycle is long, resulting in very expensive blades. The hot-end components of gas turbines, such as turbine guide vanes and turbine working blades, serve in high-temperature and high-pressure environments for a long time, and various damages of the turbine blades will inevitably occur, such as different types of damages like cracks, oxidation, corrosion, foreign object impact, wear, etc.

[0003] For the hot-end components of gas turbines found to have defects through inspection means during regular maintenance, well-known gas turbine manufacturers in the world (such as General Electric in the United States, Siemens in Germany, Mitsubishi Heavy Industries in Japan, etc.) perform welding repair on those hot-end components that meet the repair standards according to the standard repair methods, rather than directly replacing the new blades. By repair, a large amount of cost generated by blade replacement can be saved. The repair of hot-end components is generally divided into fusion welding repair and brazing repair. The fusion welding repair mainly uses tungsten inert gas welding, transferred plasma arc welding, and laser cladding technology to perform fusion welding repair on the damaged guide vanes. As Figure 1 shown, since most of the current precision-cast guide vanes are precipitation-hardened nickel-based superalloys with high Al + Ti content (such as: K452, K438, K417, Mar M247, IN939, etc.), the weldability of fusion welding becomes worse as the Al + Ti content increases. As Figure 2 shown, crystallization cracks, liquation cracks, and strain aging cracks are extremely likely to appear during the welding process. Therefore, many materials are considered non-weldable materials, and solid-solution strengthened nickel-based alloy welding wires are generally selected as fillers for fusion welding repair (such as: Inconel 625, Inconel617, Haynes230, etc.), and the strength of the weld metal is low, and the high-temperature performance is also poor. Summary of the Invention

[0004] In view of the current situation that the strength of the repaired area is relatively low after the fusion welding repair of the hot-end components of gas turbines, the purpose of the present invention is to provide a high-strength fusion welding repair method for difficult-to-weld hot-end components of gas turbines. This method does not require high-temperature preheating, nor does it require expensive laser cladding and electron beam welding equipment. By using tungsten inert gas welding (TIG) commonly used in industrial production, it is possible to achieve crack-free high-strength fusion welding repair of high-temperature alloy hot-end components of gas turbines with poor weldability, and the repaired area can achieve the effects of no cracks, no pores, and the chemical composition and mechanical properties being basically the same as those of the base metal of the component.

[0005] The technical solution of the present invention is as follows:

[0006] A high-strength fusion welding repair method for difficult-to-weld hot-end components of gas turbines. First, use a high-strength welding wire with the same or similar composition as the base metal to perform fusion welding repair on the local defects of the hot-end components of the gas turbine. Then, use a solid-solution strengthened nickel-based alloy welding filler to prepare a surfacing cladding on the outer surface of the repaired area. The hot-end components of the gas turbine after fusion welding repair are subjected to hot isostatic pressing to eliminate possible crack defects in the repaired area. Then, through machining or manual grinding, the external dimensions of the hot-end components of the gas turbine are restored, non-destructive testing is carried out, standard heat treatment is performed, and finally non-destructive testing is carried out to achieve crack-free high-strength fusion welding repair of hot-end components of gas turbines with poor weldability.

[0007] The specific steps of the high-strength fusion welding repair method for difficult-to-weld hot-end components of gas turbines are as follows:

[0008] (1) Mechanical cleaning of the repaired area

[0009] Clean the repaired area by mechanical grinding.

[0010] (2) Degreasing treatment

[0011] Degrease the repaired area with trichloroethane.

[0012] (3) Fusion welding repair with the base metal welding wire

[0013] Use the TIG welding process and a high-strength welding filler that is the same as or similar to the base metal of the hot-end components of the gas turbine to perform repair welding on the damaged area to form a surfacing repair area.

[0014] (4) Preparation of the external cladding

[0015] Use the TIG welding process and a solid-solution strengthened nickel-based alloy filler to re-surface a crack-free surfacing layer of a certain thickness on the outer surface of the surfacing repair area in step (3) as the external cladding.

[0016] (5) Perform hot isostatic pressing on the hot-end components of the gas turbine;

[0017] (6) Machining and grinding treatment of the hot-end components of the gas turbine

[0018] The size and shape of the hot-end components of the gas turbine in the repair area are restored by mechanical machining and manual grinding;

[0019] (7) Non-destructive flaw detection of the hot-end components of the gas turbine

[0020] Fluorescent and radiographic inspections are carried out on the repaired area of the hot-end components of the gas turbine, and no out-of-specification defects shall exist in the repaired area;

[0021] (8) Standard heat treatment of the hot-end components of the gas turbine

[0022] According to the material of the hot-end components of the gas turbine, the corresponding heat treatment system is selected to carry out standard heat treatment on it;

[0023] (9) Non-destructive flaw detection of the hot-end components of the gas turbine

[0024] After the hot-end components of the gas turbine are subjected to standard heat treatment, fluorescent and radiographic inspections are carried out on the whole, and no out-of-specification defects shall exist in the repaired area.

[0025] In the high-strength fusion welding repair method of the difficult-to-weld hot-end components of the gas turbine, in step (1), when cleaning the repair area, the defects existing in the hot-end components of the gas turbine are removed by mechanical grinding, the damaged area is ground into a smooth U-shaped groove, and the fluorescent detection method is used to ensure that the defects are completely removed.

[0026] In the high-strength fusion welding repair method of the difficult-to-weld hot-end components of the gas turbine, in step (3), when using the base metal wire to carry out fusion welding repair on the defects of the hot-end components of the gas turbine, the wire selected is a solid wire with a diameter of 0.8 - 1.6 mm and the same or similar composition as the base metal. The welding process uses the TIG process, the welding current is 40 - 80 A, with or without pulse function selected, the welding shielding gas uses high-purity argon, the argon gas flow rate is 5 - 10 L / min, and enough machining allowance shall be left after welding.

[0027] In the high-strength fusion welding repair method of the difficult-to-weld hot-end components of the gas turbine, if the thickness of the area to be repaired of the hot-end components of the gas turbine is relatively thin, argon protection shall be carried out on the back of the repair position.

[0028] In the high-strength fusion welding repair method of the difficult-to-weld hot-end components of the gas turbine, in step (4), when surfacing the external cladding, the welding process uses the TIG process, the wire used is a solution-strengthened nickel-based alloy with good weldability and not prone to welding cracks. The external cladding with a thickness of 0.2 - 2 mm is surfaced on the outer surface of the surfacing repair area by using the TIG process and the corresponding wire; the welding current is 40 - 60 A, with or without pulse function selected, the welding shielding gas uses high-purity argon, and the argon gas flow rate is 5 - 10 L / min.

[0029] For the high-strength fusion welding repair method of difficult-to-weld gas turbine hot-end components, if the thickness of the area to be repaired on the gas turbine hot-end component is relatively thin, argon protection needs to be carried out on the back of the repair position.

[0030] For the high-strength fusion welding repair method of difficult-to-weld gas turbine hot-end components, in step (5), the gas turbine hot-end component after welding repair is subjected to hot isostatic pressing treatment. According to the material of the gas turbine hot-end component, it is subjected to hot isostatic pressing treatment at a temperature of 1180 - 1230 °C and a pressure ≥ 120 MPa.

[0031] The design concept of the present invention is:

[0032] At present, the hot isostatic pressing technology commonly used in the manufacturing process of gas turbine hot-end components can achieve the healing treatment of oversize porosity, microcracks, creep cavities and pores in the hot-end components. This treatment process is usually only effective for closed defects and cannot eliminate open defects. During the fusion welding of nickel-based superalloys with poor weldability, open cracks are extremely likely to occur, so the hot isostatic pressing technology cannot be used to eliminate such cracks. Solution-strengthened nickel-based alloy welding fillers are often used to repair the defects of gas turbine hot-end components, and it is relatively easy to produce weld joints without welding defects by taking appropriate process measures. When using the hot isostatic pressing technology for component preparation, an external jacket is usually used. In view of the good weldability of solution-strengthened nickel-based alloys, a defect-free shielding layer with a certain thickness is re-welded on the outer surface of the gas turbine hot-end component with welding cracks using a solution-strengthened nickel-based welding filler to act as the role of the jacket. In this way, the hot isostatic pressing technology can be used to eliminate the cracks in the original repair area with cracks. The repair steps of the present invention are as follows: (1) Removal of defects in the gas turbine hot-end component; (2) Degreasing treatment of the repair area; (3) Fusion welding repair of defects using the base wire; (4) Preparation of a surfacing jacket on the outer surface of the repair area using a solution-strengthened nickel-based alloy welding filler; (5) Hot isostatic pressing treatment of the hot-end component; (6) Machining and grinding treatment of the repair area of the hot-end component; (7) Non-destructive flaw detection of the repair area of the hot-end component; (8) Standard heat treatment of the hot-end component; (9) Non-destructive testing of the hot-end component. The process flow of the present invention can achieve high-strength defect-free fusion welding repair of difficult-to-weld or non-weldable gas turbine hot-end components.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. The present invention can achieve high-strength connection of cast superalloys with poor weldability (high Al + Ti content).

[0035] 2. Since the present invention uses a repair filler with basically the same composition as the gas turbine hot-end component (such as: matrix blade), the repair area has excellent oxidation resistance and hot corrosion resistance.

[0036] 3. The repair process of the present invention can be carried out together with the hot isostatic pressing (HIP) densification of hot end components of gas turbines (such as newly cast blades and blades after service), without increasing additional welding repair costs.

[0037] 4. The present invention can expand the repair scope of hot end components of gas turbines, and will bring huge economic benefits in the future if used properly. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a diagram showing the change of weldability of superalloys with the content of Al and Ti. In the figure, the abscissa Atomic Percent, Ti represents the atomic percentage of titanium, and the ordinate Atomic Percent, Al represents the atomic percentage of aluminum.

[0039] Figure 2 It is a photo of welding cracks in high Al+Ti cast nickel-based superalloys. Among them, (a) is crystallization crack, (b) is liquefaction crack, and (c) is strain aging crack.

[0040] Figure 3 It is a schematic diagram of the welded joint prepared by the present invention (Steps 1-Steps 4). In the figure, 1 is a defect-free low-strength surfacing metal layer, 2 is a high-strength surfacing metal layer with defects, and 3 is a superalloy matrix.

[0041] Figure 4 It is a photo of fluorescent inspection of specimens. Among them, (a) is a metallographic photo of the repair area surfacing by conventional process, and (b) is a metallographic photo of the repair area prepared by the present invention.

[0042] Figure 5 It is a diagram of a damaged guide vane. Among them, (a) is an overall photo, and (b) is a local damage photo. DETAILED DESCRIPTION OF THE INVENTION

[0043] The repair of hot end components of gas turbines is a complex technological process, and its specific repair process can reach dozens of items. The present invention focuses on describing the welding repair steps, and it is default that all processes before this step, such as: dimensional measurement, visual inspection, metallographic inspection, non-destructive testing, coating removal (if any), solution heat treatment have been completed and detailed records have been made.

[0044] In the specific implementation process, the present invention provides a high-strength fusion welding repair method for difficult-to-weld hot end components of gas turbines, and the specific steps are as follows:

[0045] (1) Mechanical cleaning of the repair area

[0046] Clean the repair area by mechanical grinding; when mechanically cleaning the repair area, remove the defects existing in the hot-end components of the gas turbine by mechanical grinding, grind the damaged area into a smooth U-shaped groove, and use fluorescence detection to ensure that the defects are completely removed.

[0047] (2) Degreasing treatment

[0048] Degrease the repair area with trichloroethane.

[0049] (3) Welding repair with the base wire

[0050] Use the TIG welding process to carry out repair welding on the damaged area with high-strength welding filler that is the same as or similar to the base of the hot-end components of the gas turbine; when using the base wire for fusion welding repair of the defects of the hot-end components of the gas turbine, select a high-strength solid wire with a diameter of 0.8 - 1.6 mm and the same or similar composition as the base metal. The welding process uses the TIG process, and the welding current is 40 - 80 A. Pulse function can be selected or not. If the thickness of the area to be repaired on the hot-end components of the gas turbine is relatively thin (thickness ≤ 3 mm), argon protection is required on the back of the repair position. The welding protection gas uses high-purity argon (volume purity 99.999%), the argon flow rate is 5 - 10 L / min, and enough machining allowance should be left after welding.

[0051] (4) Preparation of the external jacket

[0052] Use the TIG welding process to re-weld a non-cracked surfacing layer with a certain thickness on the outer surface of the surfacing repair area in step (3) with a solution-strengthened nickel-based alloy filler as the external jacket; when preparing the surfacing jacket, the process used is also the TIG process, and the wire used is a solution-strengthened nickel-based alloy with good weldability and not prone to welding cracks. Use the TIG process and the corresponding wire to fully cover a certain thickness of the surfacing jacket on the outer surface of the repair area. The thickness of the surfacing jacket is 0.2 - 2 mm. The welding current is 40 - 60 A. Pulse function can be selected or not. If the thickness of the area to be repaired on the hot-end components of the gas turbine is relatively thin (thickness ≤ 3 mm), argon protection is required on the back of the repair position. The welding protection gas uses high-purity argon (volume purity 99.999%), the argon flow rate is 5 - 10 L / min.

[0053] As Figure 3 shown, the welded joint is obtained through steps (1) - (4), where: in step (3), the defect is repaired by fusion welding with the base wire, and a high-strength surfacing metal layer 2 with defects is formed at the U-shaped groove of the superalloy matrix 3; in step (4), a solution-strengthened nickel-based alloy welding filler is used to prepare a surfacing jacket on the outer surface of the repair area, and a defect-free low-strength surfacing metal layer 1 is formed on the surface of the high-strength surfacing metal layer 2 with defects.

[0054] (5) Hot isostatic pressing treatment of hot end components of gas turbines

[0055] Perform hot isostatic pressing treatment on the hot end components of gas turbines; select a temperature of 1180 - 1230 °C and a pressure ≥ 120 MPa (preferably 150 - 200 MPa) according to the material of the hot end components of gas turbines, and perform hot isostatic pressing treatment on them for 2 - 4 h.

[0056] (6) Machining and grinding treatment of hot end components of gas turbines

[0057] Adopt mechanical machining and manual grinding methods to restore the size and shape of the hot end components of gas turbines in the repair area.

[0058] (7) Non - destructive flaw detection of hot end components of gas turbines

[0059] Perform fluorescence and ray flaw detection on the repair area of the hot end components of gas turbines, and no over - standard defects shall exist in the repair area.

[0060] (8) Standard heat treatment of hot end components of gas turbines

[0061] Select the corresponding heat treatment system according to the material of the hot end components of gas turbines and perform standard heat treatment on them.

[0062] (9) Non - destructive flaw detection of hot end components of gas turbines

[0063] After the hot end components of gas turbines are subjected to standard heat treatment, perform fluorescence and ray flaw detection on the whole, and no over - standard defects shall exist in the repair area.

[0064] Next, the present invention will be further described in detail through embodiments.

[0065] Example 1:

[0066] For a certain gas turbine turbine guide vane, the vane material is Mar M247 alloy (by weight percentage, 8.5Cr - 10Co - 1.0Ti - 10W - 5.6Al - 3Ta - 0.65Mo - 0.16C - 0.04Zr - 0.015B, the rest is Ni). A porosity defect with a diameter of about 6 mm was found by fluorescence flaw detection at the large flange position. The vane material has a high Al + Ti content (6.8 wt%), and is considered an unweldable nickel - based superalloy. In the past, brazing or fusion welding repair with low - strength solution - strengthened nickel - based alloy welding wires was used.

[0067] The high - strength and effective repair can be achieved by using the present invention, and the specific repair process is as follows:

[0068] (1) Mechanical cleaning of the repair area

[0069] Use an electric straight grinder and a 4-mm-diameter cemented carbide rotary file to mechanically grind the porosity. After the porosity is no longer visible by visual inspection, perform fluorescent penetrant inspection. If porosity is still detected by the inspection, continue the grinding process until the porosity is completely removed. After the cracks are completely removed, use a rotary file to grind the damaged area into a smooth U-shaped groove.

[0070] (2) Degreasing treatment

[0071] Use trichloroethane to degrease the U-shaped groove prepared in step (1).

[0072] (3) Repair by autogenous wire fusion welding of the body

[0073] Use the TIG welding process and a K438 wire to repair weld the U-shaped groove by filling; the diameter of the K438 wire is 1.2 mm, the welding process is the TIG process, the welding current is 75 A, the welding shielding gas is high-purity argon, the argon gas flow rate is 6 L / min, and sufficient machining allowance should be left after welding.

[0074] (4) Preparation of an external jacket

[0075] When preparing the surfacing jacket, the same TIG process is used. The wire used is an Inconel625 solid wire, the welding current is 60 A, the shielding gas is high-purity argon, the argon gas flow rate is 8 L / min, and the thickness of the prepared jacket is about 0.5 mm.

[0076] (5) Hot isostatic pressing (HIP) treatment

[0077] Perform hot isostatic pressing on the gas turbine turbine guide vane together with the external jacket. The hot isostatic pressing regime is: 1220 °C / 160 MPa × 4 h, and the gas medium is argon.

[0078] (6) Machining and grinding treatment of the gas turbine turbine guide vane

[0079] Use machining and manual grinding to restore the dimensions and shape of the gas turbine turbine guide vane in the repaired area.

[0080] (7) Non-destructive inspection of the gas turbine turbine guide vane

[0081] Perform fluorescent and radiographic inspections on the repaired area of the gas turbine turbine guide vane. No out-of-specification defects shall exist in the repaired area.

[0082] (8) Standard heat treatment of the gas turbine turbine guide vane

[0083] The heat treatment process of the guide vane is as follows according to the following heat treatment regime: ① 1120 °C, hold for 2 h and air cool to room temperature; ② 850 °C, hold for 24 h and air cool to room temperature.

[0084] (9) Nondestructive Testing of Gas Turbine Turbine Guide Vanes

[0085] After the gas turbine turbine guide vanes are subjected to standard heat treatment, the whole is subjected to fluorescence and radiographic inspection, and no over-specification defects shall exist in the repair area.

[0086] Through the detection of tensile specimens prepared by the same process, the room temperature tensile strength is 927 MPa, and the high temperature (900 °C) tensile strength is 750 MPa. The tensile strengths at both temperatures exceed 90% of the strength of the original gas turbine turbine guide vanes, realizing near-equal-strength repair of large-size damage defects of gas turbine turbine guide vanes, with the advantages of no cracks, no pores in the repair area, the chemical composition being consistent with the substrate of the gas turbine turbine guide vanes, and good mechanical properties.

[0087] As Figure 4 shown, the fluorescence nondestructive testing photos prepared by the same process, where: (a) serious cracks extending from the weld metal to the substrate exist in the repair area of the conventional process surfacing, and (b) no obvious crack defects are found in the repair area (with the same welding parameters) prepared by the technology of the present invention.

[0088] Example 2:

[0089] For the three-stage guide vanes of a certain heavy-duty gas turbine, the blade material is K452 alloy (by weight percentage, 20Cr - 11Co - 2.5Al - 3.5Ti - 3.5W - 0.5Mo - 0.2Nb - 0.11C - 0.04Zr, the rest is Ni). As Figure 5 shown, there are two porosity defects in the non-critical area of the small flange plate. After grinding, a pit with a depth of about 5 mm and a diameter of 8 mm is formed. The blade material has a relatively high Al + Ti content (6.0 wt%), and there is a relatively high risk of crack occurrence during fusion welding repair.

[0090] The high-strength and effective repair can be realized by the present invention, and the specific repair process is as follows:

[0091] (1) Mechanical cleaning of the repair area

[0092] Use an electric straight grinder with a 4 mm diameter cemented carbide rotary file to mechanically grind the porosity. After the porosity is no longer visible by visual inspection, fluorescence penetrant inspection is carried out. If the inspection shows that there is still porosity, continue the grinding treatment until the porosity is completely removed. After the cracks are completely removed, use the rotary file to grind the damaged area into a smooth U-shaped groove.

[0093] (2) Degreasing treatment

[0094] The U-shaped groove prepared in step (1) is degreased with trichloroethane.

[0095] (3) Ontological wire welding repair

[0096] Use the TIG welding process to repair the ground U-shaped groove with a wire of K452 material; the diameter of the K452 wire is 1.2 mm, the welding process uses the TIG process, the welding current is 65 A, the welding shielding gas uses high-purity argon, the argon gas flow rate is 7 L / min, and enough machining allowance should be left after welding.

[0097] (4) Preparation of external jacket

[0098] When preparing the surfacing jacket, the process used is also the TIG process, the wire used is Inconel617 solid wire, the welding current is 65 A, the shielding gas is high-purity argon, the argon gas flow rate is 9 L / min, and the thickness of the prepared jacket is about 1 mm.

[0099] (5) Hot isostatic pressing (HIP) treatment

[0100] Perform hot isostatic pressing on the third-stage guide vane of the gas turbine together with the external jacket. The hot isostatic pressing system is: 1190 °C / 160 MPa × 150 min, and the gas medium uses argon.

[0101] (6) Machining and grinding treatment of the third-stage guide vane of the gas turbine

[0102] Adopt mechanical machining and manual grinding methods to restore the size and shape of the third-stage guide vane of the gas turbine in the repair area.

[0103] (7) Non-destructive flaw detection of the third-stage guide vane of the gas turbine

[0104] Perform fluorescence and ray flaw detection on the repair area of the third-stage guide vane of the gas turbine. No over-standard defects shall exist in the repair area.

[0105] (8) Standard heat treatment of the third-stage guide vane of the gas turbine

[0106] Heat-treat the guide vane according to the following heat treatment system: ① Keep it at 1170 °C for 4 h, furnace cool (15 - 30 min) to 900 °C, and air cool to room temperature; ② Keep it at 1050 °C for 4 h, and air cool to room temperature; ③ Keep it at 850 °C for 16 h, and air cool to room temperature.

[0107] (9) Non-destructive flaw detection of the third-stage guide vane of the gas turbine

[0108] After the third-stage guide vane of the gas turbine undergoes standard heat treatment, perform fluorescence and ray flaw detection on its whole body. No over-standard defects shall exist in the repair area.

[0109] Through the testing of tensile specimens prepared by the same process, the tensile strength at room temperature is 765 MPa, and the tensile strength at high temperature (900 °C) is 544 MPa. The tensile strengths at both temperatures exceed 90% of the strength of the original gas turbine's third-stage guide vane, achieving near-equal-strength repair of large-size damage defects in the gas turbine's third-stage guide vane. It has the advantages of no cracks, no pores in the repair area, the chemical composition being consistent with the blade base material, and good mechanical properties.

Claims

1. A high-strength fusion welding repair method for difficult-to-weld gas turbine hot end components, characterized in that: Firstly, a high-strength welding wire with the same or similar composition as the base material is used to perform fusion welding repair on the local defects of the hot end components of the gas turbine. Then, a solid solution-strengthened nickel-based alloy welding filler is used to prepare a cladding sleeve on the outer surface of the repair area. The hot end components of the gas turbine repaired by fusion welding are subjected to hot isostatic pressing to eliminate possible crack defects in the repair area. Then, the hot end components of the gas turbine are restored to their outer dimensions, non-destructive testing, standard heat treatment and final non-destructive testing through mechanical processing or manual grinding, thereby achieving crack-free high-strength fusion welding repair of the hot end components of the gas turbine with poor weldability.

2. The high-strength fusion welding repair method for the hot end components of a difficult-to-weld gas turbine according to claim 1, characterized in that: The specific steps are as follows: (1) Mechanical cleaning of the repair area Use mechanical grinding to clean the repair area; (2) Degreasing treatment Degrease the repair area with trichloroethane; (3) Body welding repair The TIG welding process is used to perform repair welding on the damaged area using high-strength welding fillers that are consistent with or similar to the hot end components of the gas turbine to form a surfacing repair area; (4) Preparation of external packaging Using a TIG welding process and a solid solution strengthened nickel-based alloy filler, a certain thickness of crack-free cladding layer is re-clad on the outer surface of the cladding repair area in step (3) as an additional sheath; (5) Hot isostatic pressing of hot end parts of gas turbine; (6) Machining and grinding of hot end components of gas turbines Use mechanical processing and manual grinding to restore the size and shape of the hot end components of the gas turbine in the repair area; (7) Non-destructive testing of hot end components of gas turbines Conduct fluorescent and radiographic inspection on the repair area of ​​the hot end components of the gas turbine. No defects beyond the specification shall exist in the repair area. (8) Standard heat treatment of hot end components of gas turbine According to the material of the hot end parts of the gas turbine, select the corresponding heat treatment system to carry out standard heat treatment; (9) Nondestructive testing of hot end components of gas turbines After the hot end parts of the gas turbine have undergone standard heat treatment, they shall be subjected to fluorescent and radiographic inspection as a whole, and no defects exceeding the specification shall exist in the repaired area.

3. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 2, characterized in that: In step (1), when cleaning the repair area, mechanical grinding is used to remove defects in the hot end components of the gas turbine, the damaged area is ground into a smooth U-shaped groove, and a fluorescent detection method is used to ensure that the defects are completely removed.

4. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 2, characterized in that: In step (3), when the hot end component defects of the gas turbine are repaired by fusion welding using a main body welding wire, a solid welding wire with a diameter of 0.8 to 1.6 mm and the same or similar composition as the base material is selected as the welding wire, the TIG welding process is adopted, the welding current is 40 to 80 A, with or without a pulse function, the welding shielding gas is high-purity argon gas, and the argon gas flow rate is 5 to 10 L / min. Sufficient processing allowance should be left after welding.

5. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 4, characterized in that: If the thickness of the hot end component of the gas turbine to be repaired is relatively thin, argon protection is required on the back of the repair location.

6. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 2, characterized in that: In step (4), when the overlay welding is performed, the welding process adopts the TIG process, and the welding wire used is a solid solution strengthened nickel-based alloy with good weldability and less prone to welding cracks. The TIG process and the corresponding welding wire are used to overlay the outer surface of the overlay welding repair area with an overlay welding thickness of 0.2 to 2 mm; The welding current is 40-60A, with or without pulse function. The welding shielding gas uses high-purity argon with an argon flow rate of 5-10L / min.

7. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 6, characterized in that: If the thickness of the hot end component of the gas turbine to be repaired is relatively thin, argon protection is required on the back of the repair location.

8. The high-strength fusion welding repair method for the difficult-to-weld hot end components of a gas turbine according to claim 2, characterized in that: In step (5), the hot end component of the gas turbine that has been repaired by welding is subjected to hot isostatic pressing. Depending on the material of the hot end component of the gas turbine, the hot isostatic pressing is performed at a temperature of 1180-1230° C. and a pressure of ≥120 MPa.

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