A process for producing a b-zr doped cobalt-based alloy powder and coating

Abstract

The application discloses a preparation process of B-Zr doped cobalt-based alloy powder and coating, and the alloy powder is composed of the following components with mass percentage: 90-95% of Stellite6, 1-5% of B and 1-5% of Zr. By introducing appropriate amounts of B and Zr elements into the Stellite6 alloy powder, the Zr and B elements synergistically alleviate the brittle boride to inhibit cracks, and synergistically form fine and dispersed ZrB2 and other stable high-hardness phases, promote the refinement of the structure, improve the hardness of the coating, and prevent B from forming a continuous network of brittle phases. The addition of the B element can also generate intermetallic compounds with Co elements and Cr elements, which have high hardness and high wear resistance, so that the overall strengthening layer hardness is improved. The finally formed high-hardness strengthening layer has a thickness of more than 0.5 mm and no cracks are generated. The hardness of the strengthening layer is more than 1100 HV, and the hardness of the strengthening layer can be more than 2-4 times of the substrate.

Description

Technical Field

[0001] This invention relates to the field of laser cladding strengthening technology for metal surfaces, specifically to a preparation process for B-Zr doped cobalt-based alloy powder and coating. Background Technology

[0002] 42CrMo steel, a typical medium-carbon alloy structural steel, is widely used in key fields such as heavy machinery, wind power equipment, and rail transportation due to its excellent comprehensive mechanical properties, including high hardenability, high strength, and good fatigue resistance. It has become a core structural material in these equipment systems that withstand complex alternating loads and harsh environments. However, as high-end equipment develops towards larger scale, higher efficiency, and longer service life, higher requirements are placed on the surface properties of structural materials under extreme service conditions (such as high loads, strong wear, high temperatures, and corrosive environments). Existing 42CrMo steel matrices still have certain limitations in terms of surface hardness, wear resistance, and high-temperature resistance, making them prone to surface failure that reduces the overall component lifespan. This severely restricts the further application of this material under more demanding operating conditions.

[0003] To improve the surface properties of materials, laser cladding technology, as an efficient and flexible surface modification method, has been widely used in the strengthening and repair of key components. This technology uses a high-energy laser beam to simultaneously melt a pre-prepared metal-based powder and a thin layer on the substrate surface. After rapid solidification, a reinforced cladding layer is formed that is metallurgically bonded to the substrate, thereby significantly improving the hardness, corrosion resistance, wear resistance, and specific functional properties (such as conductivity or high-temperature oxidation resistance) of the substrate surface.

[0004] Among numerous cladding materials, the traditional cobalt-based alloy Stellite6 has long held an important position in surface protection and strengthening under extreme conditions due to its superior high-temperature strength, excellent wear and corrosion resistance, good thermal fatigue resistance, and excellent toughness. It is widely used for coating protection of critical components such as aero-engines, gas turbines, and nuclear power plant valves. This type of alloy can maintain good overall performance in high-temperature and corrosive media, significantly extending the service life of components. However, when facing harsh wear conditions containing hard abrasive particles (such as SiO2 and Al2O3), the hardness of Stellite6 alloy is still insufficient, making it prone to micro-cutting and plastic deformation, leading to accelerated surface material loss. Furthermore, during continuous high-temperature service, the carbides precipitated in Stellite6 tend to coarsen and aggregate, causing a significant decrease in the macroscopic hardness of the coating. Under some conditions, the hardness decay rate can reach over 30%, seriously affecting its long-term stability and application potential under high-temperature and high-wear coupled conditions. Summary of the Invention

[0005] To address the shortcomings of existing laser cladding processes for preparing Co-based alloy coatings, such as numerous cracks, high porosity, low coverage efficiency, and low coating hardness, this invention provides a process for preparing B-Zr-doped cobalt-based alloy powder and coating. By introducing appropriate amounts of B and Zr elements into Stellite6 alloy powder and combining it with a fixed 20mm wide laser cladding process, the cladding efficiency is significantly improved. This process not only significantly enhances the coating's hardness and friction performance but also effectively reduces the probability of crack and porosity formation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a B-Zr-doped cobalt-based alloy powder, which is composed of the following components in mass percentage:

[0008] 90-95% Stellite 6, 1-5% B and 1-5% Zr.

[0009] Stellite6 is composed of Cr: 28.5-29.7%, C: 0.97-1.3%, Si: 0.8-0.99%, Mn: 0.5-0.92%, Ni: 2.07-2%, Mo: 0.24-1%, Fe: 2.1-2%, Co: balance.

[0010] In the above formulation, the addition of Zr can synergistically work with B to alleviate brittle boride cracking and form stable, high-hardness phases such as ZrB2, thereby increasing coating hardness and improving coating wettability. The addition of B can also form intermetallic compounds with Co and Cr that possess high hardness and high wear resistance, thus enhancing the overall hardness of the reinforced layer.

[0011] Extensive experimental verification has shown that the addition of boron (B) and zirconium (Zr) needs to be precisely controlled between 1% and 5%. When the addition of boron is less than 1%, the amount of hard phases such as CrB and CoB formed with the matrix is ​​insufficient, resulting in weak grain refinement and insignificant improvement in microstructure, hardness, and wear resistance. When the addition of boron is greater than 5%, continuous network borides are easily formed at grain boundaries. Although these phases have high hardness, they are extremely brittle and can become crack initiation sites.

[0012] When the amount of Zr added is less than 1%, the ability to remove impurities such as oxygen in the cladding layer is insufficient, making it difficult to form hard particles such as ZrB2 and ZrC. When the amount of Zr added is greater than 5%, coarse ZrO2 or ZrN inclusions are easily formed, which increases the melting point, leading to local stress concentration and increased porosity in the cladding layer, resulting in poor forming.

[0013] Furthermore, the B-Zr doped cobalt-based alloy powder is prepared by mixing the above-mentioned components in the specified proportions and then by acoustic resonance.

[0014] Specifically, the resonance frequency is 55 Hz, the acceleration is 60 g, and the resonance time is 10 min.

[0015] Furthermore, the particle size of the B-Zr doped cobalt-based alloy powder is 53-150 μm, and the purity is 99.99%.

[0016] The present invention also provides a B-Zr doped cobalt-based alloy coating, which is prepared on the surface of a substrate by laser cladding of the above-mentioned B-Zr doped cobalt-based alloy powder. The coating has high hardness and no pores.

[0017] The prepared B-Zr doped cobalt-based alloy coating can reach a thickness of more than 2 mm without crack formation, and the highest hardness exceeds 1100 HV, which is 2-4 times that of the 42CrMo substrate.

[0018] Furthermore, during the laser cladding process, a 20mm wide laser spot and a laser power of 6000-8000W are used to achieve a low dilution rate, uniform structure, and excellent hardness gradient distribution when the coating is clad over a large area.

[0019] Using a fixed 20mm wide spot can cover a larger area in a single cladding process, reducing the number of overlaps compared to traditional small spot (2-5 mm) cladding, thereby reducing the probability of crack and porosity formation.

[0020] When used with a fixed 20mm wide spot and a laser power of 6000-8000 W, a dense, crack-free B-Zr-doped cobalt-based alloy coating with a thickness of more than 2mm can be formed on the surface of 42CrMo steel.

[0021] Furthermore, the laser cladding scanning speed is 6-10 mm / s, and the powder feeding rate is 15-25 g / min.

[0022] Furthermore, the substrate is 42CrMo steel.

[0023] This invention also provides a process for preparing the above-mentioned B-Zr-doped cobalt-based alloy coating, comprising the following steps:

[0024] S1. Before laser cladding, the mixed B-Zr doped cobalt-based alloy powder is kept at 120℃ for 2-3 hours in a vacuum drying oven to remove moisture and dry it. The substrate is pretreated by grinding the surface of the substrate with an angle grinder to remove the oxide layer, ultrasonically cleaning the substrate to remove oil stains, and then drying it for later use.

[0025] S2. A high-hardness reinforced coating is prepared on the substrate surface by using a wide-spot laser processing system with coaxial powder feeding to deliver cobalt-doped alloy powder via laser cladding.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) This invention introduces appropriate amounts of B and Zr elements into Stellite6 alloy powder. The synergistic effect of Zr and B elements alleviates the brittle boride and inhibits cracking, and synergistically forms fine and dispersed ZrB2 and other stable high-hardness phases, which promotes the refinement of the structure, improves the hardness of the coating, and prevents B from forming a continuous network brittle phase. The addition of B element can also form intermetallic compounds with Co and Cr elements, which have high hardness and high wear resistance, thereby improving the overall hardness of the reinforced layer. The final high-hardness reinforced layer can reach a thickness of more than 0.5 mm without cracking. The hardness of the reinforced layer exceeds 1100 HV, and the hardness of the reinforced layer can be more than 2-4 times that of the substrate.

[0028] (2) This invention solves the problems of high crack rate and obvious overlap marks in large-area cladding by combining B-Zr doped Co-based alloy powder with a fixed 20mm wide laser cladding process, greatly improving cladding efficiency and realizing the preparation of a functional coating with high hardness, high density and controllable thickness on the surface of 42CrMo steel. Attached Figure Description

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 This is a macroscopic morphology diagram of the cladding layer in Example 1;

[0031] Figure 2 This is a microscopic morphology diagram of the cladding layer in Example 1;

[0032] Figure 3 This is a diagram illustrating the microhardness test of the cladding layer in Example 1;

[0033] Figure 4 This is a macroscopic morphology diagram of the cladding layer in Example 2;

[0034] Figure 5 This is a microscopic morphology diagram of the cladding layer in Example 2;

[0035] Figure 6 This is a diagram illustrating the microhardness test of the cladding layer in Example 2;

[0036] Figure 7 This is a macroscopic morphology diagram of the cladding layer in Example 3;

[0037] Figure 8 This is a microscopic morphology diagram of the cladding layer in Example 3;

[0038] Figure 9 This is a diagram illustrating the microhardness test of the cladding layer in Example 3;

[0039] Figure 10 This is a macroscopic morphology diagram of the cladding layer in Example 4;

[0040] Figure 11 This is a microscopic morphology diagram of the cladding layer in Example 4;

[0041] Figure 12 This is a diagram illustrating the microhardness test of the cladding layer in Example 4;

[0042] Figure 13 This is a macroscopic morphology diagram of the cladding layer in Example 5;

[0043] Figure 14 This is a microscopic morphology diagram of the cladding layer in Example 5;

[0044] Figure 15 This is a diagram illustrating the microhardness test of the cladding layer in Example 5;

[0045] Figure 16 This is a macroscopic morphology diagram of the cladding layer in Example 6;

[0046] Figure 17 This is a microscopic morphology diagram of the cladding layer in Example 6;

[0047] Figure 18 This is a diagram illustrating the microhardness test of the cladding layer in Example 6;

[0048] Figure 19 This is a macroscopic morphology diagram of the cladding layer in Example 7;

[0049] Figure 20 This is a microscopic morphology diagram of the cladding layer in Example 7;

[0050] Figure 21 This is a diagram illustrating the microhardness test of the cladding layer in Example 7;

[0051] Figure 22 This is a macroscopic morphology diagram of the cladding layer in Example 8;

[0052] Figure 23 This is a microscopic morphology diagram of the cladding layer in Example 8;

[0053] Figure 24 This is a diagram illustrating the microhardness test of the cladding layer in Example 8;

[0054] Figure 25 This is a macroscopic morphology diagram of the cladding layer in Comparative Example 1;

[0055] Figure 26 This is a microscopic illustration of the cladding layer in Comparative Example 1.

[0056] Figure 27 The image shows the microhardness test results of the cladding layer in Comparative Example 1.

[0057] Figure 28 The figures show the friction coefficient tests of the cladding layers in Examples 1-7 and Comparative Example 1. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in mass percentage: Stellite6 content is 94wt%, B content is 3wt%, and Zr content is 3wt%.

[0061] The above-mentioned B-Zr-doped Co-based alloy powder was prepared by mixing the components according to the specified ratio via acoustic resonance. The resonance frequency was 55 Hz, the acceleration was 60 g, and the resonance time was 10 min.

[0062] The embodiment also provides a process for preparing a high-hardness B-Zr-doped Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, comprising the following steps:

[0063] 1) Before laser cladding, the mixed B-Zr doped Co-based alloy powder was kept at 120°C for 3 hours in a vacuum drying oven to remove moisture.

[0064] 2) Substrate pretreatment: Use an angle grinder to smooth the surface of the 42CrMo bearing, remove the oxide substrate, then perform ultrasonic cleaning to remove oil stains, and blow dry for later use.

[0065] 3) A high-hardness reinforced layer was prepared on the surface of a 42CrMo bearing using a 2000W wide-spot laser processing system with coaxial powder feeding. The laser spot width was 20mm, the laser power was 7000W, the laser cladding scanning speed was 8mm / s, and the powder feeding rate was 20g / min.

[0066] Macroscopic morphology observation of the above coatings was performed, such as... Figure 1 As shown, the cladding layer is intact with virtually no cracks, pores, or peeling, and the thickness of the cladding layer can reach more than 1 mm.

[0067] Microscopic tissue observation of it, such as Figure 2 As shown, the coating consists of a light-colored matrix and dark-colored zirconium-borides. The matrix is ​​mostly composed of dense dendrites and layered lath crystals.

[0068] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 3 As shown, its highest hardness reaches 1137.9 HV.

[0069] The coating was subjected to tribological testing using a tribometer. The test load was 70 N, the rotation speed was 100 r / min, and the sample size was 5*7*15 mm. The friction coefficient curve is shown below. Figure 28 As shown, the coefficient of friction is lower than that of other embodiments, and the wear amount is 0.0135g.

[0070] Example 2

[0071] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in mass percentage: Stellite6 content is 90wt%, B content is 5wt%, and Zr content is 5wt%.

[0072] The above-mentioned B-Zr-doped Co-based copper alloy powder was prepared by acoustic resonance according to the specified composition ratio. The acoustic resonance process was the same as in Example 1.

[0073] The embodiment also provides a process for preparing a high-hardness B-Zr-doped Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Embodiment 1.

[0074] Macroscopic morphology observation of the above coatings was performed, such as... Figure 4 As shown, the increase in the amount of Zr and B added resulted in a small number of cracks and pores on the surface of the cladding layer, and the thickness of the cladding layer could reach more than 2 mm.

[0075] Microscopic tissue observation of it, such as Figure 5 As shown, the coating consists of a white matrix and dark zirconium-borides. The matrix is ​​mostly dendritic and lath crystals. Near the substrate, due to the high cooling rate, equiaxed fine-grained structures are formed in blocky regions. Continuous cracks are formed at the boundaries of structures with different morphologies.

[0076] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 6 As shown, its hardness reaches 833.6 HV.

[0077] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0425g.

[0078] Example 3

[0079] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in mass percentage: Stellite6 content is 98wt%, B content is 1wt%, and Zr content is 1wt%.

[0080] The above-mentioned B-Zr-doped Co-based copper alloy powder was prepared by acoustic resonance according to the specified composition ratio. The acoustic resonance process was the same as in Example 1.

[0081] This embodiment also provides a process for preparing a high-hardness B-Zr-doped Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as in Example 1.

[0082] Macroscopic morphology observation of the above coatings was performed, such as... Figure 7 As shown, the cladding layer is intact without cracks or peeling, and the coating thickness can reach more than 1 mm.

[0083] Microscopic tissue observation of it, such as Figure 8 As shown, the coating consists of a white matrix and dark zirconium-borides, dominated by lath crystal regions stacked in layers, while the upper right region is occupied by equiaxed fine grains and dense dendrites.

[0084] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 9 As shown, its hardness reaches 632.2 HV.

[0085] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0639g.

[0086] Example 4

[0087] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings. The composition of the B-Zr-doped Co-based alloy powder and the acoustic resonance mixing process are the same as those in Embodiment 1.

[0088] This embodiment also provides a process for preparing a high-hardness B-Zr-doped Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing. The preparation process is basically the same as that in Example 1, except that the laser power is 6000W and the laser cladding scanning rate is 6mm / s.

[0089] Macroscopic morphology observation of the above coatings was performed, such as... Figure 10 As shown, the cladding layer is intact without cracks or peeling, and the coating thickness can reach more than 1 mm.

[0090] Microscopic tissue observation of it, such as Figure 11 As shown, the morphology consists of a white matrix and dark zirconium-borides, with the matrix mainly composed of dendrites and laths.

[0091] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 12 As shown, its hardness reaches 467.3 HV.

[0092] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0727g.

[0093] Example 5

[0094] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings. The composition of the B-Zr-doped Co-based alloy powder and the acoustic resonance mixing process are the same as those in Embodiment 1.

[0095] This embodiment also provides a process for preparing a high-hardness B-Zr-doped Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing. The preparation process is basically the same as that in Example 1, except that the laser power is 8000w and the laser cladding scanning rate is 10mm / s.

[0096] Macroscopic morphology observation of the above coatings was performed, such as... Figure 13 As shown, with the increase of laser power and scanning rate, obvious cracks appeared in the cladding layer, and the thickness of the cladding layer reached more than 1 mm.

[0097] Microscopic tissue observation of it, such as Figure 14 As shown, the morphology consists of a light-colored matrix and dark-colored zirconium-borides. The matrix is ​​mostly dendrites and laths, and micropores can be observed on the upper surface of the cladding layer.

[0098] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 15 As shown, its hardness reaches 840.7 HV, which is more than twice that of the matrix.

[0099] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0455g.

[0100] Example 6

[0101] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, with the same composition and acoustic resonance mixing process as in Embodiment 2.

[0102] This embodiment also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, the process of which is as follows:

[0103] 1) Before laser cladding, the mixed B-Zr doped Co-based alloy powder was kept at 120°C for 3 hours in a vacuum drying oven to remove moisture.

[0104] 2) Substrate pretreatment: Use an angle grinder to smooth the surface of the 42CrMo bearing, remove the oxide substrate, then perform ultrasonic cleaning to remove oil stains, and blow dry for later use.

[0105] 3) A high-hardness reinforced layer was prepared on the surface of a 42CrMo bearing using a 2000W wide-spot laser processing system with coaxial powder feeding. The laser spot width was 20mm, the laser power was 6000W, the laser cladding scanning speed was 6mm / s, and the powder feeding rate was 20g / min.

[0106] Macroscopic morphology observation of the above coatings was performed, such as... Figure 16 As shown, the coating thickness can reach more than 2mm.

[0107] Microscopic tissue observation of it, such as Figure 17 As shown, the morphology is a white matrix and a dark zirconium-boride.

[0108] The hardness was tested using an automatic Vickers hardness tester, and the test results are as follows: Figure 18 As shown, its hardness reaches 737HV.

[0109] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0494g.

[0110] Example 7

[0111] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, with the same composition and acoustic resonance mixing process as in Embodiment 2.

[0112] This embodiment also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, the process of which is as follows:

[0113] 1) Before laser cladding, the mixed B-Zr doped Co-based alloy powder was kept at 120°C for 3 hours in a vacuum drying oven to remove moisture.

[0114] 2) Substrate pretreatment: Use an angle grinder to smooth the surface of the 42CrMo bearing, remove the oxide substrate, then perform ultrasonic cleaning to remove oil stains, and blow dry for later use.

[0115] 3) A high-hardness reinforced layer was prepared on the surface of a 42CrMo bearing using a 2000W wide-spot laser processing system with coaxial powder feeding. The laser spot width was 20mm, the laser power was 8000W, the laser cladding scanning speed was 10mm / s, and the powder feeding rate was 20g / min.

[0116] Macroscopic morphology observation of the above coatings was performed, such as... Figure 19 As shown, the thickness of the cladding layer exceeds 1 mm.

[0117] Microscopic tissue observation of it, such as Figure 20 As shown, the light-colored part of the coating is the matrix, and the dark-colored part is zirconium-borides. The matrix is ​​mostly lath crystals and dendrites in different orientations.

[0118] The hardness was tested using an automatic Vickers hardness tester, and the test results are as follows: Figure 21 As shown, its hardness reaches 819.7 HV.

[0119] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. The friction coefficient curve is shown below. Figure 28 As shown, the wear amount is 0.0431g.

[0120] Example 8

[0121] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, with the same composition and acoustic resonance mixing process as in Example 3.

[0122] This embodiment also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, the process of which is as follows:

[0123] 1) Before laser cladding, the mixed B-Zr doped Co-based alloy powder was kept at 120°C for 3 hours in a vacuum drying oven to remove moisture.

[0124] 2) Substrate pretreatment: Use an angle grinder to smooth the surface of the 42CrMo bearing, remove the oxide substrate, then perform ultrasonic cleaning to remove oil stains, and blow dry for later use.

[0125] 3) A high-hardness reinforced layer was prepared on the surface of a 42CrMo bearing using a 2000W wide-spot laser processing system with coaxial powder feeding. The laser spot width was 20mm, the laser power was 6000W, the laser cladding scanning speed was 6mm / s, and the powder feeding rate was 20g / min.

[0126] Macroscopic morphology observation of the above coatings was performed, such as... Figure 22 As shown, the thickness of the cladding layer exceeds 2 mm.

[0127] Microscopic tissue observation of it, such as Figure 23 As shown, the light-colored part of the coating is the matrix, and the dark-colored part is zirconium-borides. The matrix microstructure is distributed in a gradient along the thickness direction of the coating, mainly consisting of dendrites, columnar crystals, lath crystals, and equiaxed fine grains.

[0128] The hardness was tested using an automatic Vickers hardness tester, and the results are as follows: Figure 24 As shown, its maximum hardness is 676.6 HV.

[0129] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0701g.

[0130] Example 9

[0131] This embodiment provides a high-hardness B-Zr-doped Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, with the same composition and acoustic resonance mixing process as in Example 3.

[0132] This embodiment also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, the process of which is as follows:

[0133] 1) Before laser cladding, the mixed B-Zr doped Co-based alloy powder was kept at 120°C for 3 hours in a vacuum drying oven to remove moisture.

[0134] 2) Substrate pretreatment: Use an angle grinder to smooth the surface of the 42CrMo bearing, remove the oxide substrate, then perform ultrasonic cleaning to remove oil stains, and blow dry for later use.

[0135] 3) A high-hardness reinforced layer was prepared on the surface of a 42CrMo bearing using a 2000W wide-spot laser processing system with coaxial powder feeding. The laser spot width was 20mm, the laser power was 8000W, the laser cladding scanning speed was 10mm / s, and the powder feeding rate was 20g / min.

[0136] The hardness was tested using an automatic Vickers hardness tester, and the highest hardness reached 670.4 HV.

[0137] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0758g.

[0138] Comparative Example 1

[0139] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in mass percentage: Stellite6 content is 100wt%.

[0140] This embodiment also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing. The process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing in this embodiment is the same as that in Embodiment 1.

[0141] Macroscopic morphology observation of the above coatings was performed, such as... Figure 25 As shown, the cladding layer has no cracks or pores.

[0142] Microscopic tissue observation of it, such as Figure 26 As shown, the coating is mainly composed of white lath crystals and columnar crystal matrix, with a uniform microstructure.

[0143] The hardness of the coating was tested using an automatic Vickers hardness tester. Test points were taken horizontally in the upper part of the coating, with a spacing of 0.3 mm between the test points. The hardness test results are as follows: Figure 27 As shown, its highest hardness reaches 548.3 HV.

[0144] Friction and wear tests were performed on it using a friction and wear tester, and the test method was the same as in Example 1. Figure 28 The friction coefficient curve is given, and the wear amount is 0.1122g.

[0145] Comparative Example 2

[0146] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in weight percentage: 99 wt% Stellite 6, 0.5 wt% B, and 0.5 wt% Zr. The above copper alloy powder was prepared by ball milling according to the component ratio. The ball milling process is the same as in Example 1.

[0147] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0148] No defects such as cracks or pores were found in the coating.

[0149] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 589.4 HV.

[0150] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0968g.

[0151] Comparative Example 3

[0152] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components by mass percentage: 86 wt% Stellite 6, 7 wt% B, and 7 wt% Zr. The above copper alloy powder was prepared by ball milling according to the component ratio. The ball milling process is the same as in Example 1.

[0153] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0154] Macroscopic morphological observation of the above coating revealed severe cracking in the cladding layer.

[0155] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 914.1 HV.

[0156] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0354g.

[0157] Comparative Example 4

[0158] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in weight percentage: 96.5 wt% Stellite 6, 3 wt% B, and 0.5 wt% Zr. The above copper alloy powder was prepared by ball milling according to the component ratio. The ball milling process is the same as in Example 1.

[0159] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0160] Macroscopic morphological observation of the above coating showed that the cladding layer was uniform and continuous, without cracks or pores.

[0161] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 600.4 HV.

[0162] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0526g.

[0163] Comparative Example 5

[0164] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components in weight percentage: Stellite 6 content 96.5 wt%, B content 0.5 wt%, and Zr content 3 wt%. The above copper alloy powder is prepared by ball milling according to the composition ratio. The ball milling process is the same as in Example 1.

[0165] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0166] Macroscopic morphological observation of the above coating showed no obvious defects in the cladding layer.

[0167] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 560.3 HV.

[0168] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.1524g.

[0169] Comparative Example 6

[0170] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components by mass percentage: 90 wt% Stellite 6, 3 wt% B, and 7 wt% Zr. The above copper alloy powder was prepared by ball milling according to the component ratio. The ball milling process is the same as in Example 1.

[0171] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0172] Macroscopic morphological observation of the above coating revealed poor uniformity of the cladding layer, with the presence of pores and microcracks.

[0173] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 806.4 HV.

[0174] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0946g.

[0175] Comparative Example 7

[0176] This comparative example provides a high-hardness Co-based alloy powder for laser cladding on the surface of 42CrMo bearings, which is composed of the following components by mass percentage: 90 wt% Stellite 6, 7 wt% B, and 3 wt% Zr. The above copper alloy powder was prepared by ball milling according to the component ratio. The ball milling process is the same as in Example 1.

[0177] This comparative example also provides a process for preparing a high-hardness Co-based alloy coating by laser cladding on the surface of a 42CrMo bearing, and the preparation process is the same as that in Example 1.

[0178] Macroscopic morphological observation of the above coating revealed severe cracking in the cladding layer.

[0179] The hardness of the material was tested using an automatic Vickers hardness tester, and its highest hardness reached 856.8 HV.

[0180] The wear was tested using a friction and wear tester, and the test method was the same as in Example 1. The wear amount was 0.0534g.

[0181] Table 1 shows the average hardness and maximum hardness of the various embodiments and comparative examples.

[0182] Test sample Average hardness Maximum hardness Wear Example 1 1027.2HV 1137.9HV 0.0135g Example 2 743HV 833.6HV 0.0425g Example 3 599.7HV 632.2HV 0.0639g Example 4 413.9HV 467.3HV 0.0727g Example 5 727HV 840.7HV 0.0455g Example 6 681HV 737HV 0.0494g Example 7 720.6HV 819.7HV 0.0431g Example 8 566.2HV 676.6HV 0.0701g Example 9 558.9HV 670.4HV 0.0758g Comparative Example 1 523.1HV 548.3HV 0.1122g Comparative Example 2 477.1HV 589.4HV 0.0968g Comparative Example 3 703.6HV 914.1HV 0.0354g Comparative Example 4 531.9HV 600.4HV 0.0526g Comparative Example 5 426.7HV 560.3HV 0.1524g Comparative Example 6 562.1HV 806.4HV 0.0946g Comparative Example 7 707.9HV 856.8HV 0.0534g

[0183] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A B-Zr-doped cobalt-based alloy powder, characterized in that, It consists of the following components in percentage by mass: 90-95% Stellite 6, 1-5% B and 1-5% Zr; The B-Zr doped cobalt-based alloy powder is used to form a coating on the substrate surface by laser cladding. During the laser cladding process, a 20mm wide laser spot and a laser power of 6000-8000W are used. The laser cladding scanning speed is 6-10 mm / s, and the powder feeding rate is 15-25 g / min.

2. The B-Zr-doped cobalt-based alloy powder according to claim 1, characterized in that, B-Zr doped cobalt-based alloy powder is prepared by mixing the above-mentioned components in the specified proportions and then reacting them with acoustic resonance.

3. The B-Zr-doped cobalt-based alloy powder according to claim 2, characterized in that, The particle size of B-Zr doped cobalt-based alloy powder is 53-150 μm.

4. A B-Zr-doped cobalt-based alloy coating, characterized in that, It is prepared on the surface of a substrate by laser cladding of B-Zr doped cobalt-based alloy powder as described in any one of claims 1-3.

5. The B-Zr-doped cobalt-based alloy coating according to claim 4, characterized in that, During the laser cladding process, a 20mm wide laser spot and a laser power of 6000-8000W are used.

6. The B-Zr-doped cobalt-based alloy coating according to claim 5, characterized in that, The laser cladding scanning speed is 6-10 mm / s, and the powder feeding rate is 15-25 g / min.

7. The B-Zr-doped cobalt-based alloy coating according to claim 4, characterized in that, The substrate is made of 42CrMo steel.

8. A preparation process for a B-Zr-doped cobalt-based alloy coating as described in claim 4, characterized in that, Includes the following steps: S1. Before laser cladding, the B-Zr doped cobalt-based alloy powder is dried and the substrate is pretreated to remove the surface oxide layer and oil. S2. A high-hardness reinforced coating is prepared on the substrate surface by using a wide-spot laser processing system with coaxial powder feeding to deliver cobalt-doped alloy powder via laser cladding.

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