Steel piston ring groove stepped wear-resistant coating based on laser additive manufacturing and preparation method of steel piston ring groove stepped wear-resistant coating

Abstract

The invention discloses a steel piston ring groove stepped wear-resistant coating based on laser additive manufacturing and a preparation method of the steel piston ring groove stepped wear-resistant coating, and belongs to the technical field of material science and laser additive manufacturing. The wear-resistant coating is obtained by coating Fe-based soft transition powder and Fe-based hard wear-resistant powder, and the Fe-based soft transition powder comprises the following components in percentage by weight: 21 to 23 percent of Cr, 4 to 5 percent of Si, 1.5 to 2.5 percent of Mo, 12 to 14 percent of Ni, 0.1 to 0.2 percent of C, 1.4 to 1.8 percent of B and the balance of Fe; the Fe-based hard wear-resistant powder is prepared from the following components: 31 to 33 weight percent of Cr, 3.6 to 4 weight percent of Si, 1.8 to 2.1 weight percent of Ni, 3.8 to 4 weight percent of C, 1.8 to 2 weight percent of Cu, 0.3 to 0.5 weight percent of CNT, 0.3 to 0.5 weight percent of BNNT and the balance of Fe. The wear-resistant coating has a stepped structure of the soft transition layer and the hard working layer, so that the internal stress of the coating is reduced, and the bonding strength of the coating is improved; meanwhile, the high-heat-conduction phase is added and matched with the SiC hard particles, so that the performance of a high-fatigue area of the steel piston ring groove can be greatly improved, and the service life of the steel piston is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of materials science and laser additive manufacturing technology, specifically relating to a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing and its preparation method. Background Technology

[0002] Marine internal combustion engine steel piston ring grooves are prone to wear and surface failure under high temperature, high pressure, reciprocating friction, and cyclic impact loads, leading to decreased sealing performance, increased lubricant consumption, and reduced engine power and reliability. 38MnVS6 steel, due to its good machinability and medium-to-high strength, is widely used in key components such as pistons and connecting rods in marine power systems. Especially in the piston ring groove area, due to long-term exposure to high temperature, high pressure, and frequent alternating loads, wear, plastic deformation, and even fatigue fracture are highly likely, becoming typical failure sources. Currently, a commonly used method is laser cladding of a metallic coating onto the piston ring groove surface to further improve its strength. Traditional laser cladding strengthening methods often use Fe-based or Ni-based self-fluxing alloy powders, adding hard phases such as WC, etc. These coatings aim to improve hardness and wear resistance. However, while achieving high hardness, they often increase the tendency to crack, especially in thin-walled structures under complex stress conditions such as piston ring grooves, where interfacial spalling or microcrack propagation is more likely. Furthermore, some reinforcing particles have poor thermal conductivity, leading to heat accumulation and further promoting thermal cracking in the coating. Therefore, there is an urgent need to explore a laser cladding coating material and its preparation process that can significantly improve the surface hardness and wear resistance of 38MnVS6 piston ring grooves, maintain good toughness and avoid brittle fracture, and balance thermal conductivity and process economy.

[0003] Currently, there are many methods used in existing technologies to simultaneously improve the wear resistance and toughness of coatings, such as: (1) preparing Fe-Cr-C-Si series and Fe-Cr-C-Si-B series gradient coatings on 65Mn steel substrates by laser cladding technology, which significantly improves the wear resistance and toughness of the coatings; (2) adding WC to the coating, High-hardness phases improve the wear resistance of the coating, while multi-step heat treatment releases stress and reduces the generation of coating cracks. The above preparation method takes into account both the high wear resistance and toughness of the coating, but there are still many problems: (1) Insufficient thermal conductivity: Although the coating is composed of a hard working layer and a relatively soft transition layer, which significantly improves the wear resistance and toughness of the coating, the influence of high temperature environment on the wear resistance of the coating is not considered, and no high thermal conductivity phase is added, which has limitations when facing the requirements of high temperature friction conditions; (2) The contradiction between hardness and crack suppression is obvious: simply increasing WC, Although the high hardness phase can significantly improve wear resistance, it greatly increases residual tensile stress, leading to the generation of microcracks or macrocracks; although traditional multi-step heat treatment can partially release stress, it increases process complexity and cost; (3) Cost and environmental adaptability limitations: Co-based and Ni-based powders are priced high and contain high chromium and high nickel elements, resulting in high post-processing and recycling costs and significant environmental pressure. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this invention proposes a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing and its preparation method.

[0005] The technical solution adopted in this invention is: First, this invention provides a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, comprising an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially coated on the surface of the steel piston ring groove; the Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 21-23wt%, Si 4-5wt%, Mo 1.5-2.5wt%, Ni 12-14wt%, C 0.1-0.2wt%, B 1.4-1.8wt%, with the balance being Fe; the Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 31-33wt%, Si 3.6-4wt%, Ni 1.8-2.1wt%, C 3.8-4wt%, Cu 1.8-2wt%, CNT 0.3-0.5wt%, BNNT 0.3-0.5wt%, with the balance being Fe. In the above components, CNT stands for carbon nanotubes and BNNT stands for boron nitride nanotubes.

[0006] Preferably, the thickness of the Fe-based transition coating is 0.5-0.7 mm, and the thickness of the Fe-based composite wear-resistant coating is 0.8-1.1 mm.

[0007] Preferably, the particle size of both CNT and BNNT is 1-5 nm; in the above-mentioned Fe-based soft transition powder and Fe-based hard wear-resistant powder, except for CNT and BNNT, the particle size of the other components is 53-150 μm.

[0008] Secondly, this invention provides a method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, comprising the following steps: (1) Polish the surface of the substrate and then use anhydrous ethanol for ultrasonic cleaning to remove oil and other impurities. (2) Fe-based hard wear-resistant powder was ball-milled and mixed under an Ar atmosphere to obtain Fe-based hard wear-resistant ultrafine powder; (3) Dry the Fe-based hard wear-resistant ultrafine powder and the Fe-based soft transition powder obtained in step (2) respectively; (4) Using the dried Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (3) as raw materials, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are coated sequentially on the substrate treated in step (1) under Ar atmosphere to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating sequentially coated on the substrate surface.

[0009] Preferably, in step (1): the substrate is a 38MnVS6 steel plate with dimensions of 25mm×15mm×8mm.

[0010] Preferably, in step (2): the ball milling time is 3.5-4.5h and the speed is 180-220r / min.

[0011] Preferably, in step (3), the drying temperature is 70-90℃ and the time is 50-70min.

[0012] Preferably, in step (4), the coating method is laser cladding.

[0013] Preferred process parameters for laser cladding of Fe-based soft transition powder are as follows: laser power of 0.7-0.9kW, scanning speed of 5-8mm / s, overlap rate of 50%, argon flow rate of powder carrier gas of 14-16L / min, powder feeding speed of 1.5-2g / min, and spot diameter of 3mm.

[0014] Preferred process parameters for laser cladding of Fe-based hard wear-resistant ultrafine powder are as follows: laser power of 0.9-1.1kW, scanning speed of 6-9mm / s, overlap rate of 50%, argon flow rate of powder carrier gas of 14-16L / min, powder feeding speed of 2-3g / min, and spot diameter of 3mm.

[0015] The beneficial technical effects of the present invention are as follows: The wear-resistant coating provided by this invention has a stepped structure of "soft transition layer + hard working layer", which reduces the internal stress of the coating and improves the bonding strength of the coating. At the same time, by adding a specific amount of high thermal conductivity metal phase Cu and trace amounts of nano toughening phases CNT and BNNT, combined with SiC hard particles, the high fatigue zone performance of the steel piston ring groove can be significantly improved under the reciprocating friction condition of inner boundary lubrication at 300°C, thus extending the service life of the steel piston.

[0016] Specifically: (1) Significantly improves hardness and wear resistance: The hardness distributions of the hard working layer, soft transition layer and substrate are 690-760HV, 560-630HV and 240-260HV, respectively; The prepared stepped wear-resistant coating showed no cracks after being subjected to friction tests at 230℃ with a load of 20N, a frequency of 2Hz, a stroke of 10mm, a test duration of 30min, and a load of 230℃, demonstrating good high-temperature wear resistance. The average friction coefficient of the composite coating is 0.12-0.15, which is lower than that of the substrate by 0.25-0.30; Compared with the 38MnVS6 substrate, the wear resistance is improved by 40-52%, and the hardness is improved by 1.6-1.9 times; (2) Effectively suppress crack formation: By synergistically regulating thermal conductivity and stress distribution through Cu and nanotubes (CNT+BNNT), the coating is free of microcracks and interlayer delamination. (3) Improve thermal conductivity and thermal stability: By constructing thermal conductivity channels through Cu+CNT+BNNT, the thermal conductivity of the coating and its high-temperature service stability are improved; (4) Good interface bonding and dense structure: Nanotubes (CNT+BNNT) promote the uniformity of solidification structure, and obtain the dual advantages of fine grain strengthening and dense structure; (5) It has good industrialization prospects: the powder has low cost, is compatible with standard laser cladding equipment, and is suitable for mass production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, according to the present invention.

[0018] Wherein: 1-steel piston ring groove substrate; 2-Fe-based transition coating; 3-Fe-based composite wear-resistant coating. Detailed Implementation

[0019] This invention provides a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, comprising an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially coated on the surface of the steel piston ring groove; the Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 21-23wt%, Si 4-5wt%, Mo 1.5-2.5wt%, Ni 12-14wt%, C 0.1-0.2wt%, B 1.4-1.8wt%, with the balance being Fe; the Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 31-33wt%, Si 3.6-4wt%, Ni 1.8-2.1wt%, C 3.8-4wt%, Cu 1.8-2wt%, CNT 0.3-0.5wt%, BNNT 0.3-0.5wt%, with the balance being Fe.

[0020] Meanwhile, this invention provides a method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, comprising the following steps: (1) Polish the surface of the substrate and then clean it with anhydrous ethanol using ultrasonic cleaning. (2) Fe-based hard wear-resistant powder was ball-milled and mixed under an Ar atmosphere to obtain Fe-based hard wear-resistant ultrafine powder; (3) Dry the Fe-based hard wear-resistant ultrafine powder and the Fe-based soft transition powder obtained in step (2) respectively; (4) Using the dried Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (3) as raw materials, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are coated sequentially on the substrate treated in step (1) under Ar atmosphere to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating sequentially coated on the substrate surface.

[0021] This invention achieves a continuous stepped structure of "soft-hard" coating by selecting Fe-based alloy powder with specific components and contents, reducing internal stress and improving coating bonding strength. At the same time, by adding a specific amount of high thermal conductivity metal phase Cu and trace amounts of nano-toughening phases CNT and BNNT, combined with SiC hard particles, the performance of the high fatigue zone of steel piston ring groove (such as hardness, wear resistance, thermal conductivity, etc.) can be significantly improved, extending the service life of steel piston.

[0022] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0023] like Figure 1 As shown, the stepped wear-resistant coatings provided in Examples 1-3 include an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially laser-clad onto the surface of a 38MnVS6 substrate (i.e., a steel piston ring groove substrate). The Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 22wt%, Si 4.5wt%, Mo 2wt%, Ni 13wt%, C 0.15wt%, B 1.6wt%, with the balance being Fe. The Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 32wt%, Si 3.8wt%, Ni 1.9wt%, C 3.9wt%, Cu 1.9wt%, CNT 0.4wt%, BNNT 0.4wt%, with the balance being Fe. In the above-mentioned Fe-based soft transition powder and Fe-based hard wear-resistant powder, except for CNT and BNNT which have a particle size of 1-5 nm, the particle size of the other components is 53-150 μm.

[0024] Example 1 The method for preparing the stepped wear-resistant coating in this embodiment includes the following steps: (1) The substrate is made of 38MnVS6 steel plate with a size of 25mm×15mm×8mm. The surface of the substrate is polished and then ultrasonically cleaned with anhydrous ethanol to remove oil and other impurities. (2) Fe-based hard wear-resistant powder was ball-milled and mixed in an Ar atmosphere for 4 hours at a speed of 200 r / min to obtain Fe-based hard wear-resistant ultrafine powder. (3) The Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (2) are respectively placed in a vacuum dryer and dried at 80°C for 1 hour to obtain the dried powders. (4) Using the dried powders obtained in step (3) as raw materials, under an Ar atmosphere, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are sequentially laser clad onto the treated 38MnVS6 substrate obtained in step (1) to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating.

[0025] The laser cladding process parameters for the above-mentioned Fe-based soft transition powder are as follows: laser power is 0.7kW, scanning speed is 5mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 1.5g / min, and spot diameter is 3mm; the laser cladding process parameters for the above-mentioned Fe-based hard wear-resistant ultrafine powder are as follows: laser power is 0.9kW, scanning speed is 6mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 2g / min, and spot diameter is 3mm.

[0026] Testing revealed that the thickness of the stepped wear-resistant coating prepared in this embodiment was 1.3 mm, wherein the thickness of the Fe-based transition coating was 0.5 mm and the hardness was 560 HV, and the thickness of the Fe-based composite wear-resistant coating was 0.8 mm and the hardness was 690 HV. The prepared stepped wear-resistant coating showed no cracks after undergoing a high-temperature friction test at 230℃ with a load of 20 N, a frequency of 2 Hz, a stroke of 10 mm, a test duration of 30 min, and a load of 230℃, demonstrating good high-temperature wear resistance. The average coefficient of friction was 0.15, which is more than 40% higher than that of the 38MnVS6 substrate, and the hardness is increased by 1.6 times.

[0027] Example 2 The method for preparing the stepped wear-resistant coating in this embodiment includes the following steps: (1) The substrate is made of 38MnVS6 steel plate with a size of 25mm×15mm×8mm. The surface of the substrate is polished and then ultrasonically cleaned with anhydrous ethanol to remove oil and other impurities. (2) Fe-based hard wear-resistant powder was ball-milled and mixed in an Ar atmosphere for 4 hours at a speed of 200 r / min to obtain Fe-based hard wear-resistant ultrafine powder. (3) The Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (2) are respectively placed in a vacuum dryer and dried at 80°C for 1 hour to obtain the dried powders. (4) Using the dried powders obtained in step (3) as raw materials, under an Ar atmosphere, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are sequentially laser clad onto the treated 38MnVS6 substrate obtained in step (1) to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating.

[0028] The laser cladding process parameters for the above-mentioned Fe-based soft transition powder are as follows: laser power is 0.8kW, scanning speed is 6mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 1.7g / min, and spot diameter is 3mm; the laser cladding process parameters for the above-mentioned Fe-based hard wear-resistant ultrafine powder are as follows: laser power is 1.0kW, scanning speed is 8mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 2.5g / min, and spot diameter is 3mm.

[0029] Testing revealed that the thickness of the stepped wear-resistant coating prepared in this embodiment was 1.5 mm, wherein the thickness of the Fe-based transition coating was 0.6 mm and the hardness was 590 HV, and the thickness of the Fe-based composite wear-resistant coating was 0.9 mm and the hardness was 730 HV. The prepared stepped wear-resistant coating showed no cracks after undergoing a high-temperature friction test at 230℃ with a load of 20 N, a frequency of 2 Hz, a stroke of 10 mm, a test duration of 30 min, and a load of 230℃, demonstrating good high-temperature wear resistance. The average coefficient of friction was 0.13, which represents an improvement of more than 48% in wear resistance and a 1.8-fold increase in hardness compared to the 38MnVS6 substrate.

[0030] Example 3 The method for preparing the stepped wear-resistant coating in this embodiment includes the following steps: (1) The substrate is made of 38MnVS6 steel plate with a size of 25mm×15mm×8mm. The surface of the substrate is polished and then ultrasonically cleaned with anhydrous ethanol to remove oil and other impurities. (2) Fe-based hard wear-resistant powder was ball-milled and mixed in an Ar atmosphere for 4 hours at a speed of 200 r / min to obtain Fe-based hard wear-resistant ultrafine powder. (3) The Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (2) are respectively placed in a vacuum dryer and dried at 80°C for 1 hour to obtain the dried powders. (4) Using the dried powders obtained in step (3) as raw materials, under an Ar atmosphere, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are sequentially laser clad onto the treated 38MnVS6 substrate obtained in step (1) to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating.

[0031] The laser cladding process parameters for the above-mentioned Fe-based soft transition powder are as follows: laser power is 0.9kW, scanning speed is 8mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 2g / min, and spot diameter is 3mm; the laser cladding process parameters for the above-mentioned Fe-based hard wear-resistant ultrafine powder are as follows: laser power is 1.1kW, scanning speed is 9mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 15L / min, powder feeding speed is 3g / min, and spot diameter is 3mm.

[0032] Testing revealed that the thickness of the stepped wear-resistant coating prepared in this embodiment was 1.8 mm, wherein the thickness of the Fe-based transition coating was 0.7 mm and the hardness was 630 HV, and the thickness of the Fe-based composite wear-resistant coating was 1.1 mm and the hardness was 760 HV. The prepared stepped wear-resistant coating showed no cracks after undergoing a high-temperature friction test at 230℃ with a load of 20 N, a frequency of 2 Hz, a stroke of 10 mm, a test duration of 30 min, and a load of 230℃, demonstrating good high-temperature wear resistance. The average coefficient of friction was 0.12, which represents an improvement of more than 52% in wear resistance and a 1.9-fold increase in hardness compared to the 38MnVS6 substrate.

[0033] Based on the above embodiments, the present invention also has the following embodiments: Example 4 The stepped wear-resistant coating provided in this embodiment includes an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially laser-clad onto the surface of a 38MnVS6 substrate. The Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 21wt%, Si 4wt%, Mo 1.5wt%, Ni 12wt%, C 0.1wt%, B 1.4wt%, with the balance being Fe. The Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 31wt%, Si 3.6wt%, Ni 1.8wt%, C 3.8wt%, Cu 1.8wt%, CNT 0.3wt%, BNNT 0.3wt%, with the balance being Fe. Except for CNT and BNNT, which have a particle size of 1-5nm, the particle size of the remaining components in the above Fe-based soft transition powder and Fe-based hard wear-resistant powder is 53-150µm.

[0034] The preparation method of the stepped wear-resistant coating in this embodiment is the same as that in Embodiment 3.

[0035] Example 5 The stepped wear-resistant coating provided in this embodiment includes an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially laser-clad onto the surface of a 38MnVS6 substrate. The Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 23wt%, Si 5wt%, Mo 2.5wt%, Ni 14wt%, C 0.2wt%, B 1.8wt%, with the balance being Fe. The Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 33wt%, Si 4wt%, Ni 2.1wt%, C 4wt%, Cu 2wt%, CNT 0.5wt%, BNNT 0.5wt%, with the balance being Fe. Except for CNT and BNNT, which have a particle size of 1-5nm, the particle size of the remaining components in the above Fe-based soft transition powder and Fe-based hard wear-resistant powder is 53-150µm.

[0036] The preparation method of the stepped wear-resistant coating in this embodiment is the same as that in Embodiment 3.

[0037] Any parts not mentioned in the above embodiments can be implemented by adopting or referencing existing technologies. Of course, the above description is not intended to limit the invention, and the invention is not limited to the above embodiments. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should be considered within the protection scope of the invention.

Claims

1. A stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing, characterized in that, The coating comprises an Fe-based transition coating and an Fe-based composite wear-resistant coating sequentially coated on the surface of a steel piston ring groove. The Fe-based transition coating is obtained by coating with Fe-based soft transition powder, the composition of which is as follows: Cr 21-23wt%, Si 4-5wt%, Mo 1.5-2.5wt%, Ni 12-14wt%, C 0.1-0.2wt%, B 1.4-1.8wt%, with the balance being Fe. The Fe-based composite wear-resistant coating is obtained by coating with Fe-based hard wear-resistant powder, the composition of which is as follows: Cr 31-33wt%, Si 3.6-4wt%, Ni 1.8-2.1wt%, C 3.8-4wt%, Cu 1.8-2wt%, CNT 0.3-0.5wt%, BNNT 0.3-0.5wt%, with the balance being Fe.

2. The stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 1, characterized in that, The thickness of the Fe-based transition coating is 0.5-0.7 mm, and the thickness of the Fe-based composite wear-resistant coating is 0.8-1.1 mm.

3. The stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 1, characterized in that, The particle size of both CNT and BNNT is 1-5 nm; in the Fe-based soft transition powder and Fe-based hard wear-resistant powder, except for CNT and BNNT, the particle size of the other components is 53-150 μm.

4. A method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Polish the surface of the substrate and then clean it with anhydrous ethanol using ultrasonic cleaning. (2) Fe-based hard wear-resistant powder was ball-milled and mixed under an Ar atmosphere to obtain Fe-based hard wear-resistant ultrafine powder; (3) Dry the Fe-based hard wear-resistant ultrafine powder and the Fe-based soft transition powder obtained in step (2) respectively; (4) Using the dried Fe-based hard wear-resistant ultrafine powder and Fe-based soft transition powder obtained in step (3) as raw materials, Fe-based soft transition powder and Fe-based hard wear-resistant ultrafine powder are coated sequentially on the substrate treated in step (1) under Ar atmosphere to form a stepped wear-resistant coating including Fe-based transition coating and Fe-based composite wear-resistant coating sequentially coated on the substrate surface.

5. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 4, characterized in that, In step (1): the substrate is a 38MnVS6 steel plate.

6. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 4, characterized in that, In step (2): the ball milling time is 3.5-4.5h and the speed is 180-220r / min.

7. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 4, characterized in that, In step (3): the drying temperature is 70-90℃ and the time is 50-70min.

8. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 4, characterized in that, In step (4): the coating method is laser cladding.

9. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 8, characterized in that, The laser cladding process parameters for the Fe-based soft transition powder are as follows: laser power is 0.7-0.9kW, scanning speed is 5-8mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 14-16L / min, powder feeding speed is 1.5-2g / min, and spot diameter is 3mm.

10. The method for preparing a stepped wear-resistant coating for steel piston ring grooves based on laser additive manufacturing according to claim 8, characterized in that, The laser cladding process parameters for the Fe-based hard wear-resistant ultrafine powder are as follows: laser power is 0.9-1.1kW, scanning speed is 6-9mm / s, overlap rate is 50%, argon flow rate for powder carrier gas is 14-16L / min, powder feeding speed is 2-3g / min, and spot diameter is 3mm.

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