Pulse laser repairing method for aero-engine casting K438 bearing seat support

Abstract

The invention discloses a pulse laser repairing method for an aero-engine casting K438 bearing seat support, which is characterized in that most defects are repaired in advance through solution treatment, so that cracks are not easy to generate in a repaired area, and the risk is reduced. And then a welding material alloy containing a large amount of W and Mo is used for laser cladding, the tendency that carbides M3B2 and MC form a continuous net in the grain boundary can be reduced through the addition of W and Mo elements, the crack resistance is improved, the crack resistance of the welding wire is improved, it can be guaranteed that the use performance of the welding wire is similar to that of a repaired base material, the plasticity of a welding seam is improved, and the service life of the welding wire is prolonged. And defects such as weld cracks can be reduced. And meanwhile, the tempering stability is improved, so that residual stress is more effectively reduced, the abrasion resistance and corrosion resistance of a welding seam can be improved, and the problems that an existing K438 bearing seat support is high in repairing difficulty, and the stability of a repairing process is difficult to guarantee through a laser powder melting technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser repair of the surface of aircraft engine parts, and more specifically, to a pulse laser repair method for a K438 bearing seat bracket cast by an aircraft engine. Background Art

[0002] The hot end parts of aircraft engines are high-temperature alloy castings, which are subsequently machined to obtain the required size and structure. Since castings are prone to metallurgical defects such as shrinkage and inclusions during the production process, the defects are not easy to be found in the blank state, but will be exposed during machining, resulting in parts that do not meet the design requirements. For example, parts such as the K438 bearing seat bracket have dimensional tolerance problems after machining. For such problems, it is generally necessary to use repair welding / electroplating processes to repair the part size:

[0003] (1) Manual arc welding / argon tungsten arc welding / electron beam welding technology. This technology is to clean and dry the surface of the part, and then use a welding rod made of a specific material to repair the surface pits of the part. After the repair, the part has no surface pit defects, but the disadvantages are high welding heat input, large heat-affected zone, large part deformation, easy welding through of the part, and it is difficult to ensure the size of the repaired part.

[0004] (2) Electroplating / spraying technology. Plating or spraying on the location of the pits on the surface of the part can effectively repair the pits on the part, but this method is only suitable for micron-level repairs and is inefficient for millimeter-level pits. In addition, no metallurgical bond is formed between the plating / coating and the substrate, and the load-bearing capacity of the part will be greatly reduced.

[0005] However, both of the above methods are difficult to meet the performance requirements after processing, especially when welding or repairing K438 high-temperature alloy, due to the presence of strengthening phase-forming elements such as Al, Ti, and Nb in the alloy, the weldability of the alloy will deteriorate. The specific reason is that alloying elements such as Nb, Al, and Ti form γ and γ' (Ni3Al, Ni3Ti) eutectic phases, and the presence of Nb elements easily leads to Nb-rich Laves and NbC eutectic phases, and the B element in the alloy easily forms low-melting eutectic compounds such as M3B2 and MC with alloying elements such as Nb. These low-melting phases first liquefy at the grain boundary to form a liquid film under the action of welding heat cycle. Under the action of welding, they are highly sensitive to thermal cracks and are prone to cracking. In CN202111321608.0, a K438 high-temperature alloy welding method is disclosed. The process parameters are determined by adjusting the laser power, welding speed, defocusing amount, and light emission program, and the laser is concentrated on the weld for continuous welding, which can effectively suppress the tendency of thermal cracking and improve the product forming quality and weld qualification rate. This patent utilizes the characteristics of laser welding, such as small laser spot diameter, concentrated energy density, small heat input, high operational flexibility, and uniform and fine structure after repair. It has the advantages of small heat-affected zone of parts and small impact on overall performance, and can inhibit the generation of thermal cracks in K438 high-temperature alloy to a certain extent. However, when repairing defects in parts, it is necessary not only to reduce the cracks caused by a large number of low-melting eutectic phases at the grain boundaries of the alloy, but also to select suitable welding wire materials to maintain good strength with the substrate, and to reduce welding heat input through suitable welding processes, thereby reducing repair defects of parts. However, the means of improving welding quality only by controlling the process parameters of laser processing in the prior art are often insufficient, the wear resistance and plasticity of the weld are not high, and it is difficult to ensure the stability of the repair process. Summary of the invention

[0006] The main technical problem to be solved by the present invention is that the existing technology of using laser welding for K438 bearing seat bracket has the disadvantages of low wear resistance and plasticity of the weld and poor stability of the repair process. A pulse laser repair method for a K438 bearing seat bracket cast by an aircraft engine is provided.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A pulse laser repair method for an aircraft engine casting K438 bearing seat bracket, the steps comprising:

[0009] S1. Solution treat the parts, and then clean and polish the defects and the surrounding surfaces of the parts;

[0010] S2. Use alloy welding wire to perform pulse laser welding on the defective part;

[0011] The alloy welding wire comprises 14.5-16.5wt.%, Cr, 3.0-4.5wt.%, W, 15-17wt.%, Fe, 4-7wt.%, and the rest is Ni;

[0012] The pulse width of the pulse laser welding is 9 to 15 ms, the pulse peak is 2.3 to 2.9 kW, the defocus is -6 to 6 mm, and the laser energy acting on the parts is 26 to 33 J;

[0013] S3. After the repaired parts are polished and smoothed, they are subjected to aging treatment, sand blasting, and tempering to treat the residual stress to complete the repair of the aircraft engine casting bearing seat bracket.

[0014] Furthermore, the solution treatment includes heating to 1150-1170°C, keeping warm for 2-3 hours, and then cooling to room temperature. Since there are a large number of low-melting eutectic phases at the grain boundaries of the K438 alloy, cracks are easily generated in the weld. The present invention first performs a solution treatment, repairs most of the defects in advance in the solid solution state, is not prone to cracks, and improves the qualified rate of parts. Preferably, the solution treatment includes heating to 1160°C, keeping warm for 2.5 hours, and then cooling to room temperature.

[0015] Further, the cooling includes:

[0016] The first stage: the temperature in the furnace is cooled to 860-880°C at a rate of 10-15°C / min; preferably, cooled to 870°C at a rate of 12°C / min.

[0017] The second stage: the temperature in the furnace is cooled to room temperature at a cooling rate of 5 to 10°C / min; preferably, the temperature is cooled to room temperature at a cooling rate of 8°C / min.

[0018] Furthermore, the alloy welding wire comprises 15.3wt.%, Cr, 3.3wt.%, Mo, 16.1wt.%, Fe, 5.2wt.%, and the remainder is Ni.

[0019] Furthermore, the pulse laser welding parameters are preferably:

[0020] The pulse width of the pulse laser welding is 9ms, the pulse peak is 2.3kW, the defocus is -6mm, and the laser energy acting on the part is 26.90J; or

[0021] The pulse width of the pulse laser welding is 13ms, the pulse peak is 2.3kW, the defocus is 3mm, and the laser energy acting on the part is 27.58J; or

[0022] The pulse width of the pulse laser welding is 13ms, the pulse peak is 2.5kW, the defocus is 6mm, and the laser energy acting on the part is 29.66J; or

[0023] The pulse width of the pulse laser welding is 15 ms, the pulse peak is 2.3 kW, the defocusing amount is 6 mm, and the laser energy acting on the parts is 27.96 J.

[0024] Furthermore, the pulse laser welding also includes a point spacing of 0.20 to 0.50 mm, a focal length of 200 mm, and an argon gas flow rate of 5.5 to 7.5 L / min.

[0025] Furthermore, the aging treatment is to heat up to 840-850°C at 10-15°C / min, keep the temperature for 23-24h, and then cool to room temperature at a cooling rate of 5-10°C / min. During the aging treatment, the strain caused by welding residual stress and restraint stress and the plasticity reduction during the aging process cause strain aging crack sensitivity, resulting in cracks extending along the grain boundary near the fusion line. After welding, the heat affected zone of the weld is shot peened to change the welding tensile stress to compressive stress, which can effectively prevent cracks generated during the post-weld aging treatment.

[0026] Preferably, the aging treatment is performed by heating the temperature to 840°C at a rate of 12°C / min, keeping the temperature for 24 hours, and then cooling the temperature to room temperature at a rate of 8°C / min.

[0027] Furthermore, the method also includes inspecting the defects using a stereo microscope, fluorescence and X-rays.

[0028] Furthermore, if there are defects in the welding, laser repair welding is performed after tempering, aging treatment is performed, and then sand blasting is performed. After tempering to eliminate residual stress, the aircraft engine casting bearing seat bracket is repaired.

[0029] Compared with the prior art, the beneficial effects are:

[0030] The present invention first repairs most of the defects in advance through solution treatment, so that the repaired area of ​​the K438 bearing seat bracket is not prone to cracks, thereby reducing the risk. Then, a welding alloy containing more W and Mo in its composition is used for laser cladding. The addition of W and Mo elements can reduce the tendency of carbides M3B2 and MC to form a continuous network at the grain boundary, improve the crack resistance, and is beneficial to improving the crack resistance of the welding wire. It can not only ensure that the performance is similar to that of the parent material, but also increase the plasticity of the weld, which is beneficial to reducing defects such as weld cracks. At the same time, the tempering stability is improved, thereby more effectively reducing the residual stress, and in addition, the wear resistance and corrosion resistance of the weld can be improved. The present invention reduces the Al and Ti content, ensures that the subsequent aging precipitation phase γ' phase is also less, improves the plasticity while reducing the strength, and relieves the welding stress through plastic deformation.

[0031] The present invention strictly controls the laser repair parameters. Under the parameter settings of laser energy and defocus amount, the welds are well bonded, free of defects such as microcracks, unfused, and inclusions, and the repair area in the molten pool has a uniform structure, thereby improving the service life of the aircraft engine casting K438 bearing seat bracket. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a macroscopic image of a single weld under a 45x microscope;

[0033] Figure 2 It is a metallographic diagram of a single weld;

[0034] Figure 3 It is a laser repair diagram;

[0035] Among them, (a) is the surface appearance of the laser weld; (b) is the surface morphology of the molten pool; (c) is the fluorescence detection image of the weld surface; (d) is the metallographic cross-section of the repaired area;

[0036] Figure 4 These are the surface morphologies of the molten pools of welding wires with different alloys ①, ②, and ③;

[0037] Figure 5 ①The metallographic cross-section of the alloy welding wire repair area. DETAILED DESCRIPTION

[0038] The present invention will be further explained and illustrated below in conjunction with the embodiments, but the specific embodiments do not limit the present invention in any form.

[0039] The composition content (wt.%) of the aero-engine casting K438 bearing seat bracket used in the present invention mainly includes:

[0040]

[0041] Example 1

[0042] This embodiment provides a pulse laser repair method for an aircraft engine casting K438 bearing seat bracket, the steps comprising:

[0043] S1. Heat the part to 1160℃, keep it warm for 2.5h, first cool it to 870℃ at a rate of 12℃ / min, then cool it to room temperature at a rate of 8℃ / min to complete the solid solution of the part. Use fluorescence and X-ray to check the internal looseness and inclusion defects of the part, and then clean and polish the defects and the surrounding surfaces of the parts.

[0044] S2. Use alloy welding wire to perform pulse laser welding on the defective part.

[0045] The alloy welding wire comprises: Cr 15.3wt.%, W 3.3wt.%, Mo 16.1wt.%, Fe 5.2wt.%, and the rest is Ni.

[0046] The pulse width of the pulse laser welding is 9-15 ms, the pulse peak is 2.3-2.9 kW, the defocus is -6-6 mm, the laser energy acting on the parts is 26-33 J, the focal length is 200 mm, and the argon gas flow rate is 6.5 L / min.

[0047] S3. After the repaired parts are polished and smoothed, they are inspected by X-ray. If there are no obvious defects, they are subjected to aging treatment, heating to 840℃ at 12℃ / min, keeping the temperature for 24h, and then cooling to room temperature at 8℃ / min. Sand blasting and tempering are then performed to eliminate residual stress and complete the repair of the aircraft engine casting bearing seat bracket.

[0048] The specific parameter settings of pulse laser welding are shown in the following table, and single-pass tests are carried out according to these parameters.

[0049]

[0050]

[0051] The macroscopic morphology of a single weld was observed using a 45x microscope. Figure 1 As shown, there are no cracks or unfused phenomena on the molten pool surfaces of the 1-16# test pieces. The molten pools are elliptical and beautifully shaped. The welds of each molten pool are fish-scale-like after overlapping, which indicates that the welds are well bonded.

[0052] Depend on Figure 2 The metallographic observation diagram of a single weld shown in the figure shows that the molten pool morphology under different process parameters is different, which is mainly reflected in the differences in the size of the holes, the depth of the molten pool, the width of the molten pool, and the size of the stacking height. Among them, large-sized pores appeared in the molten pools of the 3#, 4#, 8#, 11#, and 16# test pieces, with diameters ranging from 0.2mm to 0.5mm; there were obvious small holes in the molten pools of the 6# and 12# test pieces, with a size less than 0.1mm. There was obvious overburning in the molten pools of the 10#, 12#, and 15# test pieces, and there was an obvious "key" effect in the molten pools of the 2#, 5#, and 7# test pieces. Compared with other parameters, the process parameter repair advantages of the 1#, 9#, 13#, and 14# test pieces are high, and no obvious holes are produced.

[0053] like Figure 3The laser repair image shown in the figure shows the surface morphology of the molten pool under a 45x microscope. (a) It can be seen from the figure that the weld surface is intact, with no surface defects or weld bumps. (b) The molten pools shown in the figure are well overlapped, with no cracks or unfused surfaces. (c) The surface of the weld point of the part shown in the figure was polished and then subjected to fluorescence detection. It was found that there were no obvious defects on the surface of the repaired position, and the subsequent X-ray detection did not find any internal defects in the molten pool, indicating that there were no obvious defects in the test piece after laser repair. (d) The metallographic cross-section of the repaired area shown in the figure shows that there are a small number of holes in the repaired area, but there are no defects such as microcracks, unfused, or inclusions, and the structure in the molten pool is uniform, with good metallurgical bonding with the K438 substrate.

[0054] Example 2

[0055] This embodiment is based on the method described in Example 1, and uses alloy welding rods of different materials for repair. The composition of the welding wire is as follows:

[0056] ① The composition of the alloy welding wire includes: Cr 20.5~23.0wt.%, W 0.2~1.0wt.%, Mo 8.0~10.0wt.%, Fe 17~20wt.%, and the rest is Ni.

[0057] ② The composition of the alloy welding wire includes: Cr 14.0~16.0wt.%, W 1.7~2.2wt.%, Mo 1.7~2.2wt.%, Al 2.4-2.8wt.%, Ti 2.1~2.5wt.%, Ni 33.0~36.0wt.%, and the rest is Fe.

[0058] ③The composition of the alloy welding wire includes: Cr 23.5~26.5wt.%, W 13.0~16.0wt.%, Al0.1-0.5wt.%, Ti 0.3~0.7wt.%, Fe 2~4wt.%, and the rest is Ni.

[0059] The pulse width of the pulse laser welding is 13 ms, the pulse peak is 2.9 kW, the defocus is +3 mm, the focal length is 200 mm, and the laser energy acting on the parts is 27.58 J.

[0060] S3. After the repaired parts are polished and smoothed, they are inspected by X-ray, subjected to aging treatment, and then sandblasted and tempered to eliminate residual stress to complete the repair of the aircraft engine casting bearing seat bracket.

[0061] Figure 4Figure 3: Surface morphology of molten pools of different alloy welding wires. (a) is the surface morphology of the molten pool of alloy ① welding wire. There are no cracks or unfused phenomena on the molten pool surface. The molten pool is elliptical and has a beautiful shape. (b) is the surface morphology of the molten pool of alloy ② welding wire. The molten pool is collapsed and the surface of the molten pool is wrinkled, which is not suitable for repair welding of K438 material. (c) is the surface morphology of the molten pool of alloy ③ welding wire. The molten pool is flat and there are obvious unfused sites. It is not suitable for pulse laser repair of K438 material.

[0062] Figure 5 This is a metallographic photo of the repaired area of ​​alloy wire ①. It can be seen from the picture that there are multiple holes and cracks in the repaired area, indicating that alloy wire ① is prone to holes and cracks under multiple welds. Therefore, alloy wire ① is not suitable for pulse laser repair of K438 material.

[0063] Example 3

[0064] This embodiment provides a pulse laser repair method for an aircraft engine casting K438 bearing seat bracket, the steps comprising:

[0065] S1. Heat the part to 1150℃, keep it warm for 3h, first cool it to 880℃ at a rate of 10℃ / min, then cool it to room temperature at a rate of 5℃ / min to complete the solid solution of the part. Use fluorescence and X-ray to check the internal looseness and inclusion defects of the part, and then clean and polish the defects and the surrounding surfaces of the parts.

[0066] S2. Use alloy welding wire to perform pulse laser welding on the defective part.

[0067] The alloy welding wire comprises 14.5wt.%, Cr, 3.0wt.%, Mo, 15wt.%, Fe, 4wt.%, and the remainder is Ni;

[0068] The pulse width of the pulse laser welding is 13 ms, the pulse peak is 2.9 kW, the defocus is +3 mm, the focal length is 200 mm, and the laser energy acting on the parts is 27.58 J.

[0069] S3. After the repaired parts are polished and smoothed, they are inspected by X-ray. If there are no obvious defects, they are subjected to aging treatment, heating to 840℃ at 10℃ / min, keeping the temperature for 24h, and then cooling to room temperature at 5℃ / min. Sand blasting and tempering are then performed to eliminate residual stress and complete the repair of the aircraft engine casting bearing seat bracket.

[0070] If there are obvious defects, laser welding is performed after the defects are removed, and aging treatment is performed after inspection. Sand blasting and tempering are then performed to eliminate residual stresses to complete the repair of the aircraft engine casting bearing seat bracket.

[0071] Example 4

[0072] This embodiment provides a pulse laser repair method for an aircraft engine casting K438 bearing seat bracket, the steps comprising:

[0073] S1. Heat the part to 1170℃, keep it warm for 2h, first cool it to 860℃ at a rate of 15℃ / min, then cool it to room temperature at a rate of 10℃ / min to complete the solid solution of the part. Use fluorescence and X-ray to check the internal looseness and inclusion defects of the part, and then clean and polish the defects and the surrounding surfaces of the parts.

[0074] S2. Use alloy welding wire to perform pulse laser welding on the defective part.

[0075] The alloy welding wire comprises 16.5wt.%, Cr, 4.5wt.%, Mo, 17wt.%, Fe, and the remainder is Ni.

[0076] The pulse width of the pulse laser welding is 13 ms, the pulse peak is 2.9 kW, the defocus is +3 mm, the focal length is 200 mm, and the laser energy acting on the parts is 27.58 J.

[0077] S3. After the repaired parts are polished and smoothed, they are inspected by X-ray. If there are no obvious defects, they are subjected to aging treatment, heating to 850℃ at 15℃ / min, keeping the temperature for 23h, and then cooling to room temperature at a cooling rate of 10℃ / min. Sand blasting and tempering are then performed to eliminate residual stress and complete the repair of the aircraft engine casting bearing seat bracket.

[0078] If there are obvious defects, laser welding is performed after the defects are removed, and aging treatment is performed after inspection. Sand blasting and tempering are then performed to eliminate residual stresses to complete the repair of the aircraft engine casting bearing seat bracket.

[0079] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A pulse laser repair method for a K438 bearing seat bracket of an aero-engine casting, characterized in that the steps include: S1. Solution treat the parts, and then clean and polish the defects and the surrounding surfaces of the parts; S2. Use alloy welding wire to perform pulse laser welding on the defective part; The alloy welding wire comprises 14.5-16.5wt.%, Cr, 3.0-4.5wt.%, W, 15-17wt.%, Fe, 4-7wt.%, and the rest is Ni; The pulse width of the pulse laser welding is 9 to 15 ms, the pulse peak is 2.3 to 2.9 kW, the defocus is -6 to 6 mm, and the laser energy acting on the parts is 26 to 33 J; S3. After the repaired parts are polished and smoothed, they are subjected to aging treatment, sand blasting, and tempering to treat the residual stress to complete the repair of the aircraft engine casting bearing seat bracket.

2. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: The solution treatment includes heating to 1150-1170° C., keeping the temperature for 2-3 hours, and then cooling to room temperature.

3. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 2 is characterized in that: The solution treatment includes heating to 1160° C., keeping the temperature for 2.5 hours, and then cooling to room temperature.

4. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 2 is characterized in that: The cooling comprises: The first stage: cooling to 860-880℃ at a rate of 10-15℃ / min; The second stage: cooling to room temperature at a cooling rate of 5 to 10°C / min.

5. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: The alloy welding wire comprises 15.3wt.%, Cr, 3.3wt.%, Mo, 16.1wt.%, Fe, 5.2wt.%, and the remainder is Ni.

6. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: The pulse laser welding parameters also include a point spacing of 0.20 to 0.50 mm, a focal length of 200 mm, and an argon gas flow rate of 5.5 to 7.5 L / min.

7. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: The aging treatment is performed by heating the temperature to 840-850° C. at a rate of 10-15° C. / min, keeping the temperature for 23-24 hours, and then cooling the temperature to room temperature at a rate of 5-10° C. / min.

8. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 7 is characterized in that: The aging treatment is performed by heating the temperature to 840°C at a rate of 12°C / min, keeping the temperature for 24 hours, and then cooling the temperature to room temperature at a rate of 8°C / min.

9. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: The method also includes inspecting for defects using stereomicroscopes, fluorescence, and X-rays.

10. The pulse laser repair method for the aircraft engine casting K438 bearing seat bracket according to claim 1 is characterized in that: If there are defects in the welding, laser repair welding, grinding, aging treatment and sand blasting are carried out after tempering. After tempering to eliminate the residual stress, the aircraft engine casting bearing seat bracket is repaired.

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