Method for repairing damage of surface carburized rod shaft accessory by laser cladding

Abstract

The invention discloses a method for repairing damage of a surface carburized rod shaft type part accessory through laser cladding. The method comprises the following steps that a surface carburized layer of the carburized rod shaft type part accessory is removed; polishing and cleaning the surface to be repaired; according to the size of the surface loss of the accessory, corresponding cladding parameters are determined, and cladding repair is conducted; carrying out stress relief annealing treatment on the cladding repair part; and according to the original size of the accessory, the redundant cladding layer is removed through a machining method, and the accessory is recovered to the original size. According to the method, a surface carburized layer is removed firstly, then cladding parameters are selected according to the removal depth, and then repairing is conducted. Meanwhile, the hardness of a cladding layer is close to or even exceeds that of a carburized layer, and the use requirement is met.

Description

Technical Field

[0001] The invention relates to the technical field of surface crack repairing of shaft parts, and more particularly to a method for laser cladding repairing of surface carburized rod shaft part accessory damage. Background Art

[0002] Aviation equipment uses a large number of rod and shaft parts in the systems of aviation, energy transmission, etc. In order to improve the surface hardness of rod and shaft parts and make the core of rod and shaft parts have high toughness during the manufacturing process of parts and accessories, carburizing treatment is usually performed. The surface hardness of the parts after carburizing usually exceeds HRC ≥ 52. Carburizing the surface of alloy steel greatly improves the surface hardness and improves its wear resistance. However, when the surface of the material is damaged, the high carbon content brings challenges to maintenance.

[0003] Generally speaking, high-carbon areas have strong hardenability, and are prone to generate large stresses during welding repairs, leading to micro and macro cracks in parts and accessories. At the same time, martensitic structures are easily formed in the heat-affected zone, which further reduces the plastic toughness. Therefore, how to repair the damaged areas on the surface of carburized parts and accessories during the overhaul and maintenance of aviation equipment has become a bottleneck problem in the repair of carburized steel parts and accessories. The present invention proposes the use of laser cladding to repair damaged rod and shaft accessories, and proposes a specific solution to the problem of easy cracking of the carburized surface by laser cladding, which can effectively guide the actual production process. Summary of the invention

[0004] In view of this, the present invention provides a method for laser cladding repair of surface carburized rod and shaft accessory damage in order to solve the problem of cracking during cladding repair of surface carburized accessory damage. The surface carburized layer is first removed, and then the cladding parameters are selected according to the removal depth, and then the repair is performed. At the same time, the hardness of the cladding layer is close to that of the carburized layer, or even exceeds that of the carburized layer, meeting the use requirements.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for laser cladding repair of surface carburized rod and shaft accessory damage, comprising the following steps:

[0007] (1) Remove the carburized layer on the surface of carburized rod and shaft accessories;

[0008] (2) Grinding and cleaning the surface to be repaired;

[0009] (3) Determine the corresponding cladding parameters according to the size of the surface loss of the parts and accessories, and perform cladding repair;

[0010] (4) Perform stress relief annealing on the cladding repaired parts;

[0011] (5) According to the original size of the parts, use machining to remove excess cladding layer and restore it to its original size.

[0012] Preferably, the hardness of the carburized rod and shaft accessories in step (1) is 52-58 HRC; the diameter of the carburized rod and shaft accessories is 8-30 mm.

[0013] Preferably, the method for determining the thickness of the carburized layer to be removed in step (1) is: based on the design drawings of carburized rod and shaft accessories, the upper limit of the carburized thickness range is used as the thickness to be removed, or samples are cut parallel to the end faces of the rod and shaft accessories in the same batch of parts, and then metallographic samples are prepared, and the thickness of the surface carburized layer is determined by a Rockwell hardness tester according to the change in hardness value.

[0014] Preferably, the polishing in step (2) is performed using sandpaper; and the cleaning is performed using acetone or alcohol.

[0015] Preferably, the carburized rod and shaft accessories in step (1) are alloy steel, and the alloy element composition is as follows: C content wt.%: 0.1-0.18, Si content wt.%: 0.5-1.2, Cr content wt.%: 10-18, Ni content wt.%: 1-5, the content of other alloy elements is less than 2wt.%, and Fe is the balance.

[0016] Preferably, the powder composition used for cladding repair in step (3) is as follows: C content wt.%: 0.14-0.16, Si content wt.%: 0.9-1.1, Cr content wt.%: 14-16, Ni content wt.%: 1.8-2.2, Mo content wt.%: 0.4-0.6, the total content of other elements does not exceed 1wt.%, and the balance is iron Fe.

[0017] Preferably, the particle size of the cladding powder in step (3) is 20-53 μm;

[0018] In the laser cladding system, the laser spot diameter is 2-2.2mm, and the powder spot diameter is 2-2.2mm;

[0019] The diameter of the part to be repaired is 8-30mm.

[0020] Preferably, during the cladding repair in step (3), a chuck is used to clamp the part to be repaired. During the cladding process, a motor drives the chuck and the part accessories to rotate, and the laser powder beam scans the surface of the part accessories to form a molten pool, and the cladding is completed after solidification.

[0021] Preferably, in step (3), when the surface loss thickness is ≤600 μm, the cladding repair is performed within the following parameter range: laser power 1750-1850 W, repair part rotation speed 55-65 r / min, powder feeding speed 2.8-3.2 r / min, laser scanning speed 1.4-1.6 mm / s;

[0022] When the surface loss thickness is between 600-1200μm, cladding repair is performed within the following parameter range: laser power 2150-2250W, repair part rotation speed 55-65r / min, powder feeding speed 3.8-4.2r / min, laser scanning speed 1.4-1.6mm / s;

[0023] When the surface loss thickness is ≥1200μm, cladding repair is performed within the following parameter range: laser power 1750-1850W, repair part rotation speed 55-65r / min, powder feeding speed 2.8-3.2r / min, laser scanning speed 1.4-1.6mm / s, or laser power 2150-2250W, repair part rotation speed 55-65r / min, powder feeding speed 3.8-4.2r / min, laser scanning speed 1.4-1.6mm / s;

[0024] Among them, surface loss thickness = original diameter of the accessory - diameter of the accessory after removing the carburized layer.

[0025] After cladding one layer as a whole, clad the next layer as a whole until the diameter of the accessory after cladding is ≥1.1*the original diameter of the accessory. Control the interlayer temperature during the cladding process, and clad the next layer when the interlayer temperature is lower than 50℃.

[0026] Preferably, in the stress relief annealing treatment of step (4), the stress relief annealing temperature is 330-370° C., the furnace is protected by argon gas, and the temperature is kept for 2-4 hours. After the temperature is kept, the furnace is cooled.

[0027] When the original size is restored in step (5), the excess cladding layer is removed by machining according to the original size of the workpiece, and then the workpiece is polished to complete the repair.

[0028] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0029] In view of the problem that the surface carburized part is prone to cracking during the cladding repair process, the present invention proposes a specific solution and method, which first removes the surface carburized layer, then selects the cladding parameters according to the removal depth, and then repairs. At the same time, the hardness of the cladding layer is close to that of the carburized layer, or even exceeds that of the carburized layer, meeting the use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] Figure 1 This is a photo of the parts after cladding operation without removing the surface carburized layer;

[0032] Figure 2 This is the microstructure of the cladding layer in Example 1;

[0033] Figure 3 This is the microstructure of the cladding layer of comparative example 1. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] The gears in a certain type of aircraft fuel system pressure pump are made of 1Cr11Ni2W2MoV, with the composition of C content wt.%: 0.15, Si content wt.%: 0.5, Cr content wt.%: 11, Ni content wt.%: 2, W content wt.%: 1.7, Mo content wt.%: 0.4, V content wt.%: 0.2, Fe is the remainder, the gear is divided into two parts, the gear shaft and the gear tooth part. In the manufacturing process, in order to increase the surface hardness of the gear and improve the wear resistance, its surface is carburized. The drawing design carburized layer depth 0.5-0.8mm, carburized layer hardness ≥ 54HRC, gear shaft diameter 10mm. In order to keep the gear stable, the gear shaft is in contact with the support end. The gear speed is extremely high during use. Long-term operation causes wear of the gear shaft and the support end, and wear and scratches on the outer surface of the gear shaft, affecting the safe operation of the gear pump.

[0037] The patented method is used for cladding repair, which specifically includes:

[0038] (1) First, the carburized layer on the surface of the gear shaft is removed by machining. According to the upper limit of the carburized layer in the drawing, the removal depth is 0.8mm. Due to the high carbon content of the carburized layer, the large stress during direct cladding can easily lead to cracking. Figure 1 In order to directly carry out cladding on the carburized layer of some accessories, cracks appear in the carburized layer.

[0039] (2) Use sandpaper to polish the surface of the gear shaft to make it smoother and flatter, and use acetone to clean the gear shaft to remove surface oil and other impurities.

[0040] (3) After measuring and removing the carburized layer, the diameter is 8.4 mm, and the thickness of the gear shaft surface loss is

[0041] 1.6mm, 1.6mm=1600μm>1200μm, the parameters selected for the first layer during the cladding process are laser power 2200W, gear shaft rotation speed 60r / min, powder feeding speed 4r / min, laser scanning speed 1.5mm / s. After cladding one layer, the diameter of the repaired gear shaft is 9.8mm. The surface temperature of the cladding layer is tested with an infrared thermometer. When the temperature is lower than 50℃, the laser power is 1800W, the rotation speed of the repaired part is 60r / min, the powder feeding speed is 3r / min, and the laser scanning speed is 1.5mm / s. The next layer is clad. After the cladding is completed, the gear shaft diameter is 10.6mm, and the cladding layer thickness is 2.2mm. 2.2>1.6*1.1, and the cladding is completed. The powder composition used for cladding is: C content wt.%: 0.15, Si content wt.%: 1, Cr content wt.%: 15, Ni content wt.%: 2, Mo content wt.%: 0.5, the total content of other elements does not exceed 1wt.%, and the balance is iron Fe. At this time, the hardness of the cladding layer is between 648-669HV, which is converted to between 57.5-58.8HRC, meeting the drawing hardness requirement of ≥54HRC; Figure 2 is the microstructure morphology of the cladding layer. Figure 2 The hardness of the cladding layer can reach 669HV; the cladding layer structure shows obvious dendrites, which is a typical morphology formed by the rapid solidification process of laser cladding.

[0042] (4) The gear is then placed in an atmosphere furnace for stress relief treatment. The atmosphere in the furnace is argon and the temperature in the furnace is 350°C. After being kept warm for 3 hours, it is cooled with the furnace.

[0043] (5) Finally, according to the dimensions of the gear shaft design drawing, the excess cladding layer is removed by machining, and the surface is polished to complete the repair.

[0044] Comparative Example 1

[0045] Comparative Example 1 The method is the same as that of Example 1, except that the cladding powder composition is carbon C content wt.%: 0.15, silicon Si content wt.%: 0.7, chromium Cr content wt.%: 18, nickel Ni content wt.%:

[0046] 2.0, the balance is iron Fe;

[0047] Figure 3 It is a conventional powder cladding morphology. The cladding layer is composed of columnar crystals and lamellar structures with a hardness of 509HV.

[0048] The powder designed in this study increased the Si element content, reduced the Cr element content, and added 0.4%-0.6% Mo. More elements were dissolved into the matrix, which improved the organization and improved the consistency of the microstructure. At the same time, the change of elements increased the hardenability of the cladding layer and significantly improved the hardness of the cladding layer.

[0049] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0050] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for laser cladding repair of surface carburized rod and shaft accessory damage, characterized in that: The following steps are involved: (1) Remove the carburized layer on the surface of carburized rod and shaft accessories; (2) Grinding and cleaning the surface to be repaired; (3) Determine the corresponding cladding parameters according to the size of the surface loss of the parts and accessories, and perform cladding repair; (4) Perform stress relief annealing on the cladding repaired parts; (5) According to the original size of the parts, use machining to remove excess cladding layer and restore it to its original size.

2. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 1, characterized in that: The hardness of the carburized rod and shaft accessories in step (1) is 52-58HRC; the diameter of the carburized rod and shaft accessories is 8-30mm.

3. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 1, characterized in that: The method for determining the thickness of the carburized layer to be removed as shown in step (1) is: based on the design drawings of carburized rod and shaft accessories, the upper limit of the carburized thickness range is used as the thickness to be removed, or samples are cut parallel to the end faces of the rod and shaft accessories in the same batch of parts, and then metallographic specimens are prepared, and the thickness of the surface carburized layer is determined by a Rockwell hardness tester based on the change in hardness value.

4. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 1, characterized in that: The polishing in step (2) is performed by using sandpaper; and the cleaning is performed by using acetone or alcohol.

5. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 1, characterized in that: The carburized rod and shaft accessories in step (1) are alloy steel, and the alloy element composition is as follows: C content wt.%: 0.1-0.18, Si content wt.%: 0.5-1.2, Cr content wt.%: 10-18, Ni content wt.%: 1-5, the content of other alloy elements is less than 2wt.%, and Fe is the balance.

6. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 5, characterized in that: The powder composition used for the cladding repair in step (3) is as follows: C content wt.%: 0.14-0.16, Si content wt.%: 0.9-1.1, Cr content wt.%: 14-16, Ni content wt.%: 1.8-2.2, Mo content wt.%: 0.4-0.6, the total content of other elements does not exceed 1wt.%, and the balance is iron Fe.

7. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 6, characterized in that: In step (3), the particle size of the cladding powder is 20-53 μm; In the laser cladding system, the laser spot diameter is 2-2.2mm, and the powder spot diameter is 2-2.2mm; The diameter of the part to be repaired is 8-30mm.

8. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 7, characterized in that: During the step (3) cladding repair, a chuck is used to clamp the part to be repaired. During the cladding process, a motor drives the chuck and the parts to rotate, and the laser powder beam scans the surface of the parts to form a molten pool, and the cladding is completed after solidification.

9. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 8, characterized in that: During the cladding repair in step (3), when the surface loss thickness is ≤600 μm, the cladding repair is performed within the following parameter range: laser power 1750-1850 W, repair part rotation speed 55-65 r / min, powder feeding speed 2.8-3.2 r / min, laser scanning speed 1.4-1.6 mm / s; When the surface loss thickness is between 600-1200μm, the following parameters are used for cladding repair: laser power 2150-2250W, repair part rotation speed 55-65r / min, powder feeding speed 3.8-4.2r / min, laser scanning speed 1.4-1.6mm / s; When the surface loss thickness is ≥1200μm, cladding repair is performed within the following parameter range: laser power 1750-1850W, repair part rotation speed 55-65r / min, powder feeding speed 2.8-3.2r / min, laser scanning speed 1.4-1.6mm / s, or laser power 2150-2250W, repair part rotation speed 55-65r / min, powder feeding speed 3.8-4.2r / min, laser scanning speed 1.4-1.6mm / s; After cladding one layer as a whole, clad the next layer as a whole until the diameter of the accessory after cladding is ≥1.1*the original diameter of the accessory. Control the interlayer temperature during the cladding process, and clad the next layer when the interlayer temperature is lower than 50℃.

10. The method for laser cladding repair of surface carburized rod and shaft accessory damage according to claim 9, characterized in that: In the stress relief annealing treatment of step (4), the stress relief annealing temperature is 330-370° C., the furnace is protected by argon gas, and the temperature is kept for 2-4 hours. After the temperature is kept, the furnace is cooled.

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