A method for preparing a metal surface particle reinforced metal matrix wear and corrosion resistant coating

Abstract

A method for preparing a wear-resistant and corrosion-resistant composite coating with particle reinforcement on a metal surface includes the following steps: (1) placing a polished titanium alloy substrate in an N2 atmosphere for laser melting and solidification treatment to prepare laser-fused TiN; (2) using particle-reinforced metal matrix powder to prepare a particle-reinforced metal matrix coating by laser cladding on the titanium alloy surface treated in step (1); (3) machining the composite coating. In the wear-resistant and corrosion-resistant composite coating prepared on the titanium alloy surface, this invention mitigates the thermal stress inside the cladding layer during the subsequent laser cladding process, resulting in excellent forming quality and no cracks in the cladding layer. The composite coating exhibits excellent wear resistance, with a wear rate of 2.02 × 10⁻⁶. ‑ 8 With a g / N·m ratio of only 6.2% of the substrate wear, the composite coating effectively mitigates the negative impacts of the composite coating on the substrate's tensile strength and thermal stress zone by treating the substrate surface with laser melting.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and specifically to a method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating. Background Technology

[0002] With the trend towards lightweight equipment, titanium alloys, due to their high specific strength and excellent corrosion resistance, are widely used in heavy-duty aerospace structural components such as aircraft landing gear. However, their relatively low hardness leads to excessive wear and failure under heavy-load friction. Therefore, research on the preparation technology of wear-resistant and corrosion-resistant surface layers for heavy-duty titanium alloys is urgently needed. Currently, wear-resistant protective treatments for titanium alloy surfaces mainly include chrome plating, thermal spraying, and laser cladding. Compared with chrome plating and thermal spraying, laser cladding technology has the following advantages: First, the cladding process is easy to control, the cladding layer is aesthetically pleasing with fewer defects, and has a good metallurgical bond with the substrate; second, laser cladding has a short laser irradiation time and a large supercooling, making it easy to obtain a fine-grained coating structure with excellent mechanical properties; third, it can achieve selective cladding, which is highly efficient and reduces material waste.

[0003] Laser cladding is used to prepare particle-reinforced metal matrix coatings. There are two main ways to add reinforcing particles: one is to directly add the reinforcing particles and the other is to generate them in situ. Traditional laser cladding wear-resistant and corrosion-resistant coatings have the following problems: First, high-energy laser beams can cause severe oxidation of the substrate and cladding powder, affecting the quality of the cladding layer; second, traditional carbide reinforcing particles are prone to burn-off at high temperatures, which increases the number of defects in the cladding layer and limits the improvement of wear-resistant and corrosion-resistant performance; third, the difference in the coefficient of thermal expansion between the cladding layer and the titanium alloy substrate is large, making it difficult to control cracks in the cladding layer. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the present invention aims to provide a method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant composite coating.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant composite coating, characterized by comprising the following steps:

[0007] (1) Laser-fused TiN was prepared by placing the polished titanium alloy matrix in a N2 atmosphere for laser melting and solidification treatment;

[0008] (2) A particle-reinforced metal cladding layer is prepared on the surface of the titanium alloy treated in step (1) by laser cladding with particle-reinforced metal matrix powder;

[0009] (3) The coating is machined.

[0010] Furthermore, in step (1), a vacuum is first drawn to below 0.005 MPa, and then N2 is introduced until the pressure is 0.3 to 1 MPa.

[0011] Furthermore, in step (1), the laser power of laser melting is 0.4 to 2 kW, the moving distance of the laser generator's spray gun is 5 to 15 mm / s, the defocusing amount is 10 to 30 mm, and the thickness of the laser-melted TiN obtained is 0.2 to 0.5 mm.

[0012] Furthermore, in step (2), the reinforcing particles in the particle-reinforced metal matrix powder are nitride particles such as cBN and TiN or boride particles such as TiB2 and CrB2, and the metal matrix is ​​a NiCr, CoCr binary alloy, CoCrFeNiTi system or AlCrFeNiTi system high entropy alloy.

[0013] Furthermore, in the particle-reinforced metal matrix powder, the mass percentage of reinforcing particles is 5-15%.

[0014] More preferably, the reinforcing particles are cBN, and the metal matrix is ​​a CoCrFeNiTi high-entropy alloy.

[0015] Furthermore, in step (2), the laser power of the laser cladding is 0.8 to 2.4 kW, the moving distance of the spray gun of the laser generator is 10 to 25 mm / s, the defocusing amount is 10 to 30 mm, the powder feeding rate is 0.5 to 1.5 rpm, and the thickness of the cladding layer is 1 to 10 mm.

[0016] When preparing metal-based coatings on the substrate surface by laser cladding, it was found that the difference in the coefficient of thermal expansion between the titanium alloy substrate and the wear-resistant and corrosion-resistant coating is large, which can induce the initiation of cracks in the cladding layer, resulting in poor cladding quality. During the wear process, obvious weak points will appear, the cracks will further expand, and even cause partial peeling of the coating.

[0017] In the preparation process, the substrate was first subjected to laser melting and solidification treatment under an N2 atmosphere, which induced the in-situ formation of TiN particles with high hardness and high coefficient of thermal expansion. Compared with traditional laser cladding and other processing methods, the in-situ formation of TiN particles reduced the heat-affected zone of the substrate and improved the microhardness of the substrate. In addition, the laser melting and solidification of the substrate served as a preheating process, alleviating the thermal stress inside the cladding layer during the subsequent laser cladding process. Furthermore, the coefficient of thermal expansion of the TiN particles generated by laser melting and solidification was 9.4 × 10⁻⁶. -6 / k, higher than the coefficient of thermal expansion of titanium alloy (8.6×10). -6 / k) can act as a transition layer between the titanium alloy substrate and a specific metal-based cladding layer, further mitigating thermal stress. Under this dual mitigation, the forming quality of the subsequently prepared cladding layer is significantly improved.

[0018] Furthermore, the machining process involves first using a grinding wheel to grind the cladding layer to a predetermined specification, ensuring a roughness of <3.2, and then using nylon polishing cloth in conjunction with diamond polishing agent to polish the surface roughness of the coating to <1.0.

[0019] Most specifically, a method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating is characterized by comprising the following steps:

[0020] (1) The titanium alloy substrate was polished in sequence with 180#, 400#, 600# and 800# sandpaper to remove oil stains and oxide film and other impurities from its surface;

[0021] (2) Place the titanium alloy substrate on a two-degree-of-freedom rotating platform, turn on the vacuum pump of the atmosphere chamber to pump the pressure inside the chamber to below 0.005MPa, and then introduce N2 to make the pressure inside the chamber reach a positive pressure state of 0.3 to 1MPa.

[0022] (3) Laser melting TiN is prepared on the surface of titanium alloy substrate by turning on the laser, wherein the laser power is 0.4 to 2 kW, the spray gun moving distance is 5 to 15 mm / s, the defocusing amount is 10 to 30 mm, the turntable speed is 20 to 100 r / min, and the thickness of the prepared laser melting TiN is 0.2 to 0.5 mm.

[0023] (4) A particle-reinforced metal matrix cladding layer is prepared by laser cladding on the surface of the titanium alloy matrix after step (3) using particle-reinforced metal matrix powder. The laser power is 0.8-2.4kW, the spray gun moving distance is 10-25mm / s, the defocusing amount is 10-30mm, the powder feeding rate is 0.5-1.5rpm, the turntable speed is 20-100r / min, and the cladding layer thickness is 1-5mm. The particle-reinforced metal matrix powder is a sintered spherical powder after the reinforcing particles and the metal matrix are agglomerated and granulated, with a particle size of 50-150μm. The reinforcing particles are nitride particles such as cBN and TiN or boride particles such as TiB2 and CrB2. The metal matrix is ​​a binary alloy of NiCr and CoCr, a CoCrFeNiTi system or an AlCrFeNiTi system high entropy alloy.

[0024] (5) According to the required component structure and size, the titanium alloy surface is ground and polished to achieve a surface roughness of <1.0, so as to obtain the required titanium alloy surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating component.

[0025] Although nitrides or borides are directly added as reinforcing particles in this invention, it was found during the preparation process that under the action of high-energy lasers, reinforcing particles such as cBN decompose to form free atoms, which combine with Ti, Cr and other atoms in the metal matrix with extremely low mixing enthalpy to form a composite composition of various hard particles such as TiN, TiB2, and CrB2. Compared with the original cBN particles, these composite hard particles are uniformly dispersed in the cladding layer, which enhances the wear resistance of the coating.

[0026] The present invention has the following technical effects:

[0027] This invention provides a wear-resistant and corrosion-resistant composite coating for titanium alloy surfaces. This coating mitigates the thermal stress within the cladding layer during subsequent laser cladding, resulting in excellent cladding quality, no cracks, and superior wear resistance (wear rate of 2.02 × 10⁻⁶). -8 With a g / N·m ratio of only 6.2% of the substrate wear, the composite coating effectively mitigates the negative impacts of the composite coating on the substrate's tensile strength and thermal stress zone by treating the substrate surface with laser melting. Attached Figure Description

[0028] Figure 1 The cross-sectional microstructure and composition of the CoCrFeNiTi-cBN cladding layer prepared in this invention.

[0029] Figure 2 XRD pattern of the CoCrFeNiTi-cBN cladding layer prepared in this invention.

[0030] Figure 3 Macroscopic morphology of the CoCrFeNiTi-cBN cladding layer prepared in this invention.

[0031] Figure 4 Hardness variation curves of the coatings prepared in each comparative example and Example 1. Detailed Implementation

[0032] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0033] Example 1

[0034] A method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating includes the following steps:

[0035] (1) The TC18 titanium alloy substrate was polished in sequence with 180#, 400#, 600# and 800# sandpaper to remove oil stains and oxide film and other impurities from its surface;

[0036] (2) Place the TC18 substrate on a two-degree-of-freedom rotary platform, turn on the vacuum pump of the atmosphere chamber to pump the pressure inside the chamber to below 0.005MPa, and then introduce N2 to make the pressure inside the chamber reach a positive pressure state of 0.5MPa.

[0037] (3) Laser melting TiN was prepared on the surface of titanium alloy substrate by turning on the laser, wherein the laser power was 1kW, the spray gun moving distance was 10mm / s, the defocusing amount was 20mm, the turntable speed was 60r / min, and the thickness of the prepared laser melting TiN was 0.5mm.

[0038] (4) A particle-reinforced metal matrix cladding layer was prepared by laser cladding on the surface of the titanium alloy matrix after step (3) using CoCrFeNiTi-cBN powder. The laser power was 1.2kW, the spray gun moving distance was 20mm / s, the defocusing amount was 20mm, the powder feeding rate was 1.0rpm, the turntable speed was 80r / min, and the cladding layer thickness was 2mm. The CoCrFeNiTi-cBN powder was a sintered spherical powder after the reinforcing particles cBN and the metal matrix CoCrFeNiTi were agglomerated and granulated at a mass ratio of 6:94, with a particle size of 50-150μm.

[0039] (5) According to the required component structure and size, the titanium alloy surface is ground and polished to achieve a surface roughness of <1.0, so as to obtain the required titanium alloy surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating component.

[0040] Figure 1 The cross-sectional microstructure and composition of the composite coating prepared in Example 1 are shown in the figure. The cladding layer consists of a large area of ​​light gray structure 3, unmelted granular dark gray structure 2, and diffusely distributed black structure 1. Combined with EDS energy dispersive spectroscopy analysis, the light gray structure 1 is mainly composed of five elements: Co, Cr, Fe, Ni, and Ti, indicating that it is mainly a primitive CoCrFeNiTi high-entropy alloy structure. For the dark gray structure 2, high-melting-point elements such as Cr, Mo, and V show obvious segregation, while the content of low-melting-point elements such as Co, Fe, and Ni is significantly reduced compared to region 3. At the same time, structure 2 exhibits the morphology of unmelted particles, which is analyzed to be formed by the reaction of high-melting-point elements with atoms such as B and N (Cr, Mo, V, Ti). x B y (Cr,Mo,V,Ti) x N yRefractory compounds; for black structure 1, it is mainly composed of Ti and N elements with an atomic ratio close to 1:1. Since the mixing enthalpy of Ti and N is extremely low, free N atoms preferentially combine with excess Ti atoms to form TiN phase in situ. Furthermore, as the cBN content increases, the number of free B and N atoms in the molten pool increases, TiN gradually increases, and the dispersion strengthening effect increases.

[0041] Figure 2 The phase composition of the CoCrFeNiTi-cBN cladding layer is shown in the figure. No obvious cBN diffraction peaks are observed in the cladding layer. Instead, high-melting-point compound phases such as TiN, TiB, TiB2, and Cr2N are present. Furthermore, the diffraction peaks of TiN, TiB, and TiB2 gradually increase with the increase of cBN content. This phenomenon indicates that cBN is fully melted and decomposed under the action of a high-energy laser beam. B and N atoms are in a free state in the molten pool and first combine with cations with lower enthalpy of mixing to form compounds such as TiN, TiB, and TiB2, which then precipitate. Since the enthalpy of mixing of B and N atoms is high, the priority for them to combine with each other to form compounds after ionization is low. Therefore, there are no obvious cBN diffraction peaks in the XRD pattern of the cladding layer.

[0042] Comparative Example 1:

[0043] Compared with Example 1, no laser melting treatment was performed. Instead, the CoCrFeNiTi-cBN cladding layer was directly prepared by laser melting on the substrate surface. The remaining steps were the same as in Example 1.

[0044] Figure 3 (a) and (b) show the morphology of the composite coatings prepared on the surface of titanium alloy TC18 substrate in Comparative Example 1 and Example 1, respectively, in the cladding state and the ground state. It can be seen that after grinding the cladding layer on the substrate surface, the CoCrFeNiTi-cBN cladding layer prepared directly on the substrate surface in Comparative Example 1 showed obvious cracks and poor forming quality. However, in Example 1, due to the preparation of fused TiN by laser melting and solidification and sufficient preheating of the substrate, the prepared CoCrFeNiTi-cBN cladding layer still maintained a relatively dense structure after grinding and did not produce cracks, resulting in excellent coating forming quality.

[0045] Friction and wear test:

[0046] Before the friction and wear test, the cladding layer was polished with 600#, 1000#, and 1500# SiC sandpaper in sequence. After polishing, the surface roughness of the cladding layer was <0.1. The test temperature was (20±5)℃, the relative humidity was (30±5)%, the grinding workpiece was an Al2O3 ball with a diameter of 5mm, the test load was 20N, the reciprocating length was 3mm, the reciprocating frequency was 5Hz, and the test time was 1800s. After the test, the wear mark size and wear volume of the coating were measured by laser confocal microscope and the mass wear rate was calculated by formula (1).

[0047] K=Vρ / (P×L) (1)

[0048] In the formula: K is the wear rate; V is the wear volume; ρ is the coating density; P is the normal load; L is the total slip distance.

[0049] Wear track tests were conducted on the TC18 substrate, the monolayer structure of the CoCrFeNiTi-cBN cladding layer directly prepared on the substrate surface in Comparative Example 1, and the bilayer structure of the laser-fused TiN+ cladding layer in Example 1. The wear track widths of the three samples were found to be 1167.6 μm, 594.7 μm, and 384.2 μm, respectively; the cross-sectional areas of the wear tracks were 6869.4 μm. 2 492.2μm 2 and 273.7μm 2 The wear rate is shown in Table 1.

[0050] Table 1: Mass Wear Rate of CoCrFeNiTi-cBN Cladding Layer

[0051]

[0052] As can be seen from the table above, the mass wear rate of the single-layer cladding structure in Comparative Example 1 and the double-layer structure of the laser-fused TiN+ cladding layer in Example 1 is significantly lower than that of the substrate, and both significantly improve the wear resistance of the TC18 substrate. However, the mass wear rate of the composite coating prepared in Example 1 of this invention is even lower.

[0053] Comparative Example 2:

[0054] Compared to Example 1, a TiN cladding layer was prepared on the substrate surface using laser cladding, followed by the preparation of a CoCrFeNiTi-cBN cladding layer. It is difficult to achieve micron-level coating thicknesses using laser cladding.

[0055] from Figure 4As can be seen, this invention generates TiN reinforcing particles in situ on the substrate surface. These particles have a hardness between that of the cladding layer and the substrate, exhibiting excellent toughness and providing good transition performance. In contrast, in Comparative Example 1, the cladding layer is directly prepared on the substrate surface without any intermediate transition. In Comparative Example 2, a pure TiN layer is prepared using laser cladding. Its thickness is significantly greater than the in-situ grown TiN particle layer, reaching millimeter levels, and its hardness is much higher than that of the cladding layer (>1400 HV). 0.5 The cladding material has poor toughness and performs an unsatisfactory transition function, resulting in low bonding strength and easy peeling. Furthermore, after grinding, a small number of cracks were found in the cladding layer, and its mass wear rate was 5.09 × 10⁻⁶ according to the same friction and wear test. -8 g / N·m.

[0056] The tensile strength of the titanium alloy components with composite coatings prepared in Comparative Example 2 and Example 1 was tested, and the results are shown in Table 2.

[0057] Table 2: Variation in average tensile strength

[0058] Style Name Average tensile strength (MPa) TC18 matrix 1080 Comparative Example 2 774 Example 1 1036

[0059] As shown in the table above, the TiN transition layer prepared by laser cladding in Comparative Example 2 has a large heat-affected zone, making it unsuitable for thin-walled materials. Furthermore, the resulting composite coating significantly affects the original mechanical properties of the substrate. Additionally, the laser cladding process requires TiN powder raw materials, making the process more complex and costly. In contrast, the present invention uses laser-fused TiN to prepare a CoCrFeNiTi-cBN cladding layer. The resulting composite coating has less impact on the original mechanical properties of the substrate, allowing the substrate to maintain good original mechanical properties.

[0060] Example 2

[0061] A method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating includes the following steps:

[0062] (1) The titanium alloy TC4 substrate was polished in sequence with 180#, 400#, 600# and 800# sandpaper to remove oil stains and oxide film and other impurities from its surface;

[0063] (2) Place the TC4 substrate on a two-degree-of-freedom rotating platform, turn on the vacuum pump of the atmosphere chamber to pump the pressure inside the chamber to below 0.005MPa, and then introduce N2 to make the pressure inside the chamber reach a positive pressure of 0.3MPa.

[0064] (3) Laser melting TiN was prepared on the surface of titanium alloy substrate by turning on the laser, wherein the laser power was 0.4kW, the spray gun moving distance was 5mm / s, the defocusing amount was 10mm, the turntable speed was 20r / min, and the thickness of the prepared laser melting TiN was 0.2mm.

[0065] (4) A particle-reinforced metal matrix cladding layer was prepared by laser cladding on the surface of the titanium alloy matrix after step (3) using NiCr-TiN powder. The laser power was 2.4kW, the spray gun moving distance was 25mm / s, the defocusing amount was 30mm, the powder feeding rate was 1.5rpm, the turntable speed was 100r / min, and the cladding layer thickness was 5mm. The NiCr-TiN powder was a sintered spherical powder after the reinforcing particles TiN and metal matrix NiCr were agglomerated and granulated at a mass ratio of 10:90, with a particle size of 50-150μm.

[0066] (5) According to the required component structure and size, the titanium alloy surface is ground and polished to achieve a surface roughness of <1.0, so as to obtain the required titanium alloy surface particle-reinforced metal matrix wear-resistant and corrosion-resistant composite coating component.

[0067] In this embodiment, a titanium alloy substrate with a composite coating was prepared and subjected to friction and wear tests. The mass wear rate was 2.26 × 10⁻⁶. -8 (g / N·m), with an average tensile strength of 1019 MPa.

[0068] Example 3

[0069] A method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating includes the following steps:

[0070] (1) The TC18 titanium alloy substrate was polished in sequence with 180#, 400#, 600# and 800# sandpaper to remove oil stains and oxide film and other impurities from its surface;

[0071] (2) Place the TC18 substrate on a two-degree-of-freedom rotary platform, turn on the vacuum pump of the atmosphere chamber to pump the pressure inside the chamber to below 0.005MPa, and then introduce N2 to make the pressure inside the chamber reach a positive pressure of 1MPa.

[0072] (3) Laser melting TiN was prepared on the surface of titanium alloy substrate by turning on the laser, wherein the laser power was 2kW, the spray gun moving distance was 15mm / s, the defocusing amount was 30mm, the turntable speed was 100r / min, and the thickness of the prepared laser melting TiN was 0.3mm.

[0073] (4) Using AlCrFeNiTi-TiB2 powder, a particle-reinforced metal matrix cladding layer is prepared by laser cladding on the surface of the titanium alloy matrix after step (3). The laser power is 0.8kW, the spray gun moving distance is 10mm / s, the defocusing amount is 10mm, the powder feeding rate is 0.5rpm, the turntable speed is 20r / min, and the cladding layer thickness is 1mm. The AlCrFeNiTi-TiB2 powder is a sintered spherical powder after the reinforcing particles TiB2 and the metal matrix AlCrFeNiTi are agglomerated and granulated at a mass ratio of 15:85, with a particle size of 50~150μm.

[0074] (5) According to the required component structure and size, the titanium alloy surface is ground and polished to achieve a surface roughness of <1.0, so as to obtain the required titanium alloy surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating component.

[0075] In this embodiment, a titanium alloy substrate with a composite coating was prepared and subjected to friction and wear tests. The mass wear rate was 2.17 × 10⁻⁶. -8 (g / N·m), with an average tensile strength of 1025MPa.

Claims

1. A method for preparing a metal surface particle-reinforced metal-based wear-resistant and corrosion-resistant coating, characterized in that, Includes the following steps: (1) The polished titanium alloy substrate was placed in a N2 atmosphere for laser melting and solidification treatment to prepare laser-melted TiN. The laser power was 0.4~2kW, the spray gun moving distance of the laser generator was 5~15mm / s, the defocusing amount was 10~30mm, and the thickness of the laser-melted TiN was 0.2~0.5mm. (2) A particle-reinforced metal matrix cladding layer is prepared by laser cladding of particle-reinforced metal matrix powder on the surface of titanium alloy after step (1). The reinforcing particles in the particle-reinforced metal matrix powder are cBN, TiN nitride particles or TiB2, CrB2 boride particles, and the metal matrix is ​​NiCr, CoCr binary alloy, CoCrFeNiTi system or AlCrFeNiTi system high entropy alloy. (3) Machining the surface of the substrate.

2. The method for preparing a metal surface particle-reinforced metal matrix wear-resistant and corrosion-resistant coating as described in claim 1, characterized in that: In step (1), a vacuum is first drawn to below 0.005 MPa, and then N2 is introduced until the pressure is 0.3~1 MPa.

3. The method for preparing a metal surface particle-reinforced metal matrix wear-resistant and corrosion-resistant coating as described in claim 2, characterized in that: In step (2), the laser power of laser cladding is 0.8~2.4kW, the spray gun moving distance of the laser generator is 10~25mm / s, the defocusing amount is 10~30mm, and the powder feeding rate is 0.5~1.5rpm.

4. The method for preparing a metal surface particle-reinforced metal matrix wear-resistant and corrosion-resistant coating as described in claim 3, characterized in that: In step (3), the machining process first involves using a grinding wheel to grind the cladding layer to a predetermined specification, ensuring a roughness of <3.

2. Then, a nylon polishing cloth is used in conjunction with a diamond polishing agent to polish the surface roughness of the coating to <1.0.

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