Stainless steel surface treatment method and stainless steel material

Abstract

The invention discloses a stainless steel surface treatment method and a stainless steel material. The stainless steel surface treatment method comprises the following steps: S1, carrying out roughening pretreatment on a stainless steel substrate; s2, NiCr-Cr3C2 gas atomization powder is adopted as a raw material; and S3, the raw materials are sprayed on the surface of the stainless steel base body in a cold spraying mode, and the corrosion-resistant coating is formed on the surface of the stainless steel base body. The NiCr-Cr3C2 powder is used as the raw material, the corrosion-resistant coating is formed on the surface of the stainless steel in a cold spraying mode, high bonding strength, low porosity and excellent corrosion resistance are achieved, and the comprehensive service performance of the stainless steel material in nuclear power, chemical engineering, ocean and other extreme environments can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of metal surface engineering technology, and in particular to a stainless steel surface treatment method and stainless steel material. Background Technology

[0002] 316L stainless steel is widely used in critical fields such as nuclear power equipment, chemical pipelines, and ship components due to its excellent corrosion resistance and mechanical properties. However, in seawater service environments, 316L stainless steel may still experience problems such as localized corrosion, crevice corrosion, and pitting corrosion, affecting the structural integrity and service life of components.

[0003] To further enhance surface protection performance, researchers have widely adopted metal-ceramic composite coating technology in recent years. Among them, the NiCr-Cr3C2 system, with its excellent corrosion resistance, oxidation resistance, and high hardness, has been widely used in the field of protective coatings. NiCr alloys possess excellent corrosion resistance and thermal stability, while Cr3C2 ceramic particles can significantly improve the hardness, wear resistance, and erosion resistance of the coating. The combination of the two can achieve a synergistic "metal-ceramic" enhancement effect.

[0004] Cold spraying technology, as a solid-state deposition process, utilizes a high-speed carrier gas flow to drive metal powder to impact and deposit on the substrate surface at room temperature or low temperature, avoiding material structure changes and oxidation problems that may occur during high-temperature processes. Its deposited coating has high adhesion, low porosity, and low residual stress, making it particularly suitable for constructing protective coatings on the surfaces of heat-sensitive materials. Existing cold spraying research mainly focuses on aluminum and titanium alloy surfaces, but systematic research is still lacking in the preparation of high-density, high-adhesion nickel-based corrosion-resistant coatings on the surface of 316L stainless steel components. Traditional thermal spraying technologies (such as supersonic flame spraying and plasma spraying) often face the following problems in the deposition of such metal-ceramic composite coatings: (1) High temperature leads to powder oxidation and embrittlement, which seriously affects the phase stability of Cr3C2 and the bonding ability of NiCr; (2) Thermal stress easily causes the coating to crack or fall off, especially when deposited on heat-sensitive metals such as stainless steel; (3) Uneven interface bonding and insufficient density affect long-term corrosion resistance and service reliability. Therefore, there is an urgent need for a new cold spraying process and material system suitable for 316L stainless steel, which can achieve the construction of high-quality nickel-based coatings and have excellent corrosion resistance to meet the long-term service requirements under harsh working conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a stainless steel surface treatment method and stainless steel material that improves the overall service performance of stainless steel.

[0006] The technical solution adopted by this invention to solve its technical problem is: to provide a stainless steel surface treatment method, comprising the following steps: S1. Roughen the stainless steel substrate to make its surface roughness 3μm ~ 6μm; S2. NiCr-Cr3C2 gas atomization powder is used as raw material, and the particle size of NiCr-Cr3C2 gas atomization powder is 5μm~45μm; S3. The raw material is sprayed onto the surface of the stainless steel substrate by cold spraying to form a NiCr-Cr3C2 corrosion-resistant coating with a thickness of 150μm to 450μm on the surface of the stainless steel substrate.

[0007] Preferably, in step S1, the roughening pretreatment includes sandblasting.

[0008] Preferably, the sandblasting process includes: using alumina sand particles with a particle size of 600μm to 700μm as the sandblasting material, and sandblasting the stainless steel substrate under a compressed air pressure of 0.4MPa to 0.6MPa; after completion, cleaning with ethanol and deionized water in sequence to remove oil stains and drying.

[0009] Preferably, in step S3, the stainless steel substrate is cold-sprayed using a cold spraying device; The cold spraying parameters are as follows: the spraying gas is nitrogen, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and uniform deposition is carried out by reciprocating scanning method, with the deposition thickness controlled at 150μm ~ 450μm.

[0010] Preferably, the stainless steel surface treatment method further includes the following steps: S4. S4 is ultrasonically cleaned sequentially with ethanol and deionized water, and then dried.

[0011] Preferably, the stainless steel substrate is 316L stainless steel.

[0012] The present invention also provides a stainless steel material, comprising a stainless steel substrate and a NiCr-Cr3C2 corrosion-resistant coating formed on the surface of the stainless steel substrate by cold spraying.

[0013] Preferably, the raw material for the NiCr-Cr3C2 corrosion-resistant coating includes NiCr-Cr3C2 gas atomized powder with a particle size of 5μm to 45μm, a spherical or near-spherical powder morphology, and an oxygen content of ≤0.5 wt%.

[0014] Preferably, the NiCr-Cr3C2 gas atomization powder comprises NiCr and Cr3C2 in a mass ratio of 80~90:10~20.

[0015] Preferably, the stainless steel substrate is 316L stainless steel.

[0016] The beneficial effects of this invention are as follows: using NiCr-Cr3C2 powder as raw material, a NiCr-Cr3C2 corrosion-resistant coating is formed on the surface of stainless steel by cold spraying. The NiCr-Cr3C2 corrosion-resistant coating has high bonding strength, low porosity and excellent corrosion resistance, which can significantly improve the comprehensive service performance of stainless steel materials (such as 316L stainless steel) in extreme environments such as nuclear power, chemical industry and marine environment. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 These are surface micrographs of the corrosion-resistant coatings in the embodiments and comparative examples of this invention; Figure 2 These are cross-sectional microscopic images of the corrosion-resistant coatings in the embodiments and comparative examples of this invention; Figure 3 This is a comparison diagram of the polarization curves of the corrosion-resistant coatings in the embodiments and comparative examples of this invention. Detailed Implementation

[0018] A stainless steel surface treatment method according to an embodiment of the present invention includes the following steps: S1. Roughen the stainless steel substrate to achieve a surface roughness of 3μm to 6μm.

[0019] The roughening pretreatment includes sandblasting to make the surface roughness of the stainless steel substrate meet the requirements for coating adhesion.

[0020] Sandblasting can include: using alumina sand particles with a particle size of 600μm~700μm (24 mesh) as the sandblasting material, and sandblasting the stainless steel substrate under a compressed air pressure of 0.4MPa~0.6MPa.

[0021] In other embodiments, the roughening pretreatment may also be performed by turning to make the surface roughness of the stainless steel substrate meet the requirements for coating adhesion.

[0022] After the roughening pretreatment is completed, the stainless steel substrate is cleaned with ethanol and deionized water in sequence to remove oil stains and then dried.

[0023] In one embodiment, the stainless steel substrate is 316L stainless steel.

[0024] S2. NiCr-Cr3C2 gas atomized powder is used as raw material to ensure good powder flowability during drying.

[0025] In NiCr-Cr3C2 gas atomized powder, the preferred mass ratio of NiCr to Cr3C2 is 80~90:10~20. For example, the mass ratio of NiCr to Cr3C2 is 90:10 or 80:20.

[0026] The NiCr-Cr3C2 gas atomized powder is obtained by mixing NiCr and Cr3C2 in a set ratio, followed by sintering, powdering, and gas atomization.

[0027] The NiCr-Cr3C2 atomized powder has a particle size of 5μm~45μm, and excessively coarse or fine powder is removed by sieving. The NiCr-Cr3C2 atomized powder has a spherical or near-spherical morphology and an oxygen content ≤0.5 wt%. The atomized powder morphology is beneficial for subsequent coating deposition.

[0028] S3. The raw material is sprayed onto the surface of the stainless steel substrate by cold spraying to form a NiCr-Cr3C2 corrosion-resistant coating on the surface of the stainless steel substrate.

[0029] The thickness of the NiCr-Cr3C2 corrosion-resistant coating is 150μm to 450μm.

[0030] Among them, cold spraying equipment is used to cold spray the stainless steel substrate.

[0031] The cold spraying parameters are as follows: the spraying gas is nitrogen, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and uniform deposition is carried out by reciprocating scanning method, with the deposition thickness controlled at 150μm ~ 450μm.

[0032] By controlling the deposition thickness, a NiCr-Cr3C2 corrosion-resistant coating of the corresponding thickness was obtained.

[0033] In one embodiment, the stainless steel surface treatment method further includes the following steps: S4. The stainless steel substrate that has been cold-sprayed is then ultrasonically cleaned with ethanol and deionized water in sequence, and then dried.

[0034] After the above is completed, the stainless steel samples are characterized, including thickness measurement, microstructure observation and electrochemical corrosion test, to ensure that the quality of the NiCr-Cr3C2 corrosion-resistant coating meets the application requirements.

[0035] Based on the above-described stainless steel surface treatment method, a treated stainless steel material can be obtained. This stainless steel material includes a stainless steel substrate and a NiCr-Cr3C2 corrosion-resistant coating formed on the surface of the stainless steel substrate by cold spraying.

[0036] The present invention will be further described below through specific embodiments.

[0037] Example 1: 1) Substrate pretreatment: Select a 316L stainless steel plate with dimensions of 20mm × 20mm × 3mm as the substrate material. Pretreatment of the 316L stainless steel substrate includes sandblasting with 24-mesh (approximately 600 to 700μm) alumina sand particles at a compressed air pressure of 0.4MPa to 0.6MPa, followed by rinsing with deionized water and drying in cold air for later use.

[0038] 2) Preparation of cold spray powder: Select NiCr-10Cr3C2 gas atomization powder with an average particle size of 15μm ~ 45μm and an oxygen content of less than 0.1%. Place the powder in a vacuum drying oven and dry it at 120℃ for 3 hours to remove surface adsorbed water.

[0039] 3) Cold spraying process parameters: High-pressure nitrogen is used as the accelerating carrier gas, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and a reciprocating scanning method is used for uniform deposition. 4) Post-treatment process: After cold spraying, the coating is ultrasonically cleaned with ethanol and deionized water and then dried for later use.

[0040] 5) Performance Testing Microstructure: The surface and cross-sectional morphology of the coating were observed using a scanning electron microscope, such as... Figure 1 (b) and Figure 2 As shown in (b), the results show that the interface is tightly bonded, the coating has obvious pores, and the average thickness is about 310 μm.

[0041] Corrosion resistance: Electrochemical polarization tests were conducted in a 3.5 wt% NaCl solution, and the polarization curves are shown below. Figure 3 As shown.

[0042] Example 2: 1) Substrate pretreatment: Select a 316L stainless steel plate with dimensions of 20mm×20mm×3mm as the substrate material. Pretreatment of the 316L stainless steel substrate includes sandblasting with 24-mesh (approximately 600 to 700μm) alumina sand particles at a compressed air pressure of 0.4MPa~0.6MPa, followed by rinsing with deionized water and drying in cold air for later use.

[0043] 2) Preparation of cold spray powder: Select NiCr-20Cr3C2 gas atomization powder with an average particle size of 15μm ~ 45μm and an oxygen content of less than 0.1%. Place the powder in a vacuum drying oven and dry it at 120℃ for 3 hours to remove surface adsorbed water.

[0044] 3) Cold spraying process parameters: High-pressure nitrogen is used as the accelerating carrier gas, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and a reciprocating scanning method is used for uniform deposition. 4) Post-treatment process: After cold spraying, the coating is ultrasonically cleaned with ethanol and deionized water and then dried for later use.

[0045] 5) Performance Testing Microstructure: The surface and cross-sectional morphology of the coating were observed using a scanning electron microscope, such as... Figure 1 (c) and Figure 2 As shown in (c), the results show that the interface is tightly bonded, the coating has obvious pores, and the average thickness is about 310 μm.

[0046] Corrosion resistance: Electrochemical polarization tests were conducted in a 3.5 wt% NaCl solution, and the polarization curves are shown below. Figure 3 As shown, the corrosion resistance of the sample prepared from NiCr-10Cr3C2 in Example 1 is higher.

[0047] Comparative Example 1: 1) Substrate pretreatment: Select a 316L stainless steel plate with dimensions of 20mm×20mm×3mm as the substrate material. First, pretreatment of the 316L stainless steel substrate is carried out, including sandblasting with 24-mesh (about 600 to 700μm) alumina sand particles under a compressed air pressure of 0.4MPa~0.6MPa. Then, rinse with deionized water and dry in cold air for later use.

[0048] 2) Preparation of cold spray powder: Select NiCr composite powder with an average particle size of 15μm~45μm and an oxygen content of less than 0.1%. Place the powder in a vacuum drying oven and dry it at 120℃ for 3 hours to remove surface adsorbed water.

[0049] 3) Cold spraying process parameters: High-pressure nitrogen is used as the accelerating carrier gas, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and a reciprocating scanning method is used for uniform deposition. 4) Post-treatment process: After cold spraying, the coating is ultrasonically cleaned with ethanol and deionized water and then dried for later use.

[0050] 5) Performance Testing Microstructure: The surface and cross-sectional morphology of the coating were observed using a scanning electron microscope, such as... Figure 1 (a) and Figure 2 As shown in (a), the results show that the interface area has obvious voids, the coating is dense and without obvious pores, and the average thickness is about 427 μm.

[0051] Corrosion resistance: Electrochemical polarization tests were conducted in a 3.5 wt% NaCl solution, and the polarization curves are shown below. Figure 3 As shown, the corrosion resistance is significantly lower than that of the sample prepared from NiCr-10Cr3C2, exhibiting poor corrosion resistance.

[0052] In summary, the stainless steel surface treatment method of the present invention achieves high-density deposition of NiCr-Cr3C2 coating on the surface of 316L stainless steel. The resulting coating has low porosity, which is significantly better than the traditional thermal spraying process. The solid-state cold spraying method avoids high-temperature oxidation and structural changes, maintains the integrity of the coating composition, and ensures stable and reliable performance. The preparation process is green and environmentally friendly, easy to operate, and has strong engineering feasibility and industrial promotion prospects.

[0053] The stainless steel material obtained by the present invention meets the surface protection, repair and remanufacturing requirements of high-end equipment in extreme environments; it significantly improves its corrosion resistance in seawater environments, effectively blocks the erosion of corrosive media such as chloride ions in seawater, significantly slows down the corrosion process, and extends the service life of the material. It is suitable for anti-corrosion applications of nuclear power pipelines, valve components and other components that are exposed to seawater environments for a long time.

[0054] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for surface treatment of stainless steel, characterized in that, Includes the following steps: S1. Roughen the stainless steel substrate to make its surface roughness 3μm ~ 6μm; S2. NiCr-Cr3C2 gas atomization powder is used as raw material, and the particle size of NiCr-Cr3C2 gas atomization powder is 5μm~45μm; S3. The raw material is sprayed onto the surface of the stainless steel substrate by cold spraying to form a NiCr-Cr3C2 corrosion-resistant coating with a thickness of 150μm to 450μm on the surface of the stainless steel substrate.

2. The stainless steel surface treatment method according to claim 1, characterized in that, In step S1, the roughening pretreatment includes sandblasting.

3. The stainless steel surface treatment method according to claim 2, characterized in that, The sandblasting process includes: using alumina sand particles with a particle size of 600μm to 700μm as the sandblasting material, and sandblasting the stainless steel substrate under a compressed air pressure of 0.4MPa to 0.6MPa; after completion, cleaning with ethanol and deionized water in sequence to remove oil stains and drying.

4. The stainless steel surface treatment method according to claim 1, characterized in that, In step S3, the stainless steel substrate is cold-sprayed using a cold spraying device; The cold spraying parameters are as follows: the spraying gas is nitrogen, the spraying gas pressure is 4.0 MPa ~ 4.5 MPa, the gas preheating temperature is 600℃ ~ 650℃, the spraying distance is 20mm ~ 25mm, the spray gun moving speed is 50mm / s ~ 100 mm / s, and uniform deposition is carried out by reciprocating scanning method, with the deposition thickness controlled at 150μm ~ 450μm.

5. The stainless steel surface treatment method according to any one of claims 1-4, characterized in that, It also includes the following steps: S4. Washed sequentially with ethanol and deionized water, then dried.

6. The stainless steel surface treatment method according to any one of claims 1-4, characterized in that, The stainless steel substrate is 316L stainless steel.

7. A stainless steel material, characterized in that, It includes a stainless steel substrate and a NiCr-Cr3C2 corrosion-resistant coating formed on the surface of the stainless steel substrate by cold spraying.

8. The stainless steel material according to claim 7, characterized in that, The raw material for the NiCr-Cr3C2 corrosion-resistant coating includes NiCr-Cr3C2 gas atomized powder with a particle size of 5μm~45μm, a spherical or near-spherical morphology, and an oxygen content of ≤0.5wt%.

9. The stainless steel material according to claim 7, characterized in that, The NiCr-Cr3C2 gas atomization powder comprises NiCr and Cr3C2 in a mass ratio of 80~90:10~20.

10. The stainless steel material according to any one of claims 7-9, characterized in that, The stainless steel substrate is 316L stainless steel.

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