A method for preparing a corrosion and wear resistant coating on a magnesium alloy surface

Abstract

The application provides a method for preparing a corrosion-resistant and wear-resistant coating on a magnesium alloy surface, comprising the following steps: (1) performing sand blasting roughening treatment on the surface of a magnesium alloy base body; (2) performing oil removal and dirt removal treatment on the surface of the magnesium alloy base body after the sand blasting roughening treatment; (3) forming a cold spraying coating on the oil-removed and dirt-removed surface of the magnesium alloy base body by adopting a cold spraying process; and (4) melting and cladding a laser cladding coating on the surface of the magnesium alloy base body with the cold spraying coating by adopting a laser cladding process. The application first deposits a tantalum coating on the surface of the magnesium alloy by adopting the cold spraying process, and then melts and clads a nickel-based-spherical porous alloy tungsten carbide wear-resistant and corrosion-resistant coating on the surface of the tantalum coating, so that the magnesium alloy base body can be protected, the magnesium alloy has excellent corrosion resistance and wear resistance while the lightweight characteristics of the magnesium alloy are basically maintained, and the service life of the magnesium alloy is significantly prolonged, and the application range of the magnesium alloy is expanded.

Description

Technical Field

[0001] This invention belongs to the field of surface technology, and specifically relates to a method for preparing an anti-corrosion and wear-resistant coating on the surface of a magnesium alloy. Background Technology

[0002] Magnesium alloys possess high specific strength, excellent vibration damping, thermal conductivity, and electromagnetic shielding capabilities, making them a promising candidate for applications in the automotive, 3C (computer, communication, and consumer electronics) industries, rail transportation, aerospace, and lightweight weaponry sectors. They are hailed as "green engineering materials of the 21st century." Magnesium alloys also exhibit low density, high specific strength, high specific stiffness, and high damping tolerance, making them valuable in aerospace applications. However, their extremely low natural corrosion potential makes them highly susceptible to corrosion. Furthermore, their corrosion resistance is even worse in humid climates, significantly limiting their industrial applications. Laser cladding of alloys or alloy ceramic coatings offers excellent wear resistance and corrosion resistance, but magnesium alloys are highly reactive and have a low melting point. Direct laser cladding on magnesium alloy surfaces often results in oxidation and burn-off, making the cladding process very difficult. Additionally, laser cladding of nickel-based tungsten carbide often uses spherical solid tungsten carbide particles. These particles have smooth surfaces and large masses, making it easy for spherical tungsten carbide to settle to the bottom during the cladding process. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing a coating that improves the corrosion resistance and wear resistance of magnesium alloys. While maintaining its lightweight characteristics, the magnesium alloy also has excellent corrosion resistance and wear resistance, thereby significantly extending the service life of the magnesium alloy and expanding its application range.

[0004] To achieve the above technical objectives, the technical solution adopted in this embodiment of the invention is: a method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface, comprising the following steps:

[0005] (1) The surface of the magnesium alloy substrate is roughened by sandblasting;

[0006] (2) The surface of the magnesium alloy substrate after sandblasting roughening in step (1) is degreased and cleaned;

[0007] (3) A cold spray coating is formed on the surface of the magnesium alloy substrate after degreasing and cleaning in step (2) using a cold spray process;

[0008] (4) A laser cladding coating is applied to the surface of the magnesium alloy substrate with the cold spray coating in step (3).

[0009] Furthermore, in step (1), white corundum sand with a particle size of 36~60 mesh is used for sandblasting roughening treatment, and the compressed air pressure used during sandblasting is 0.4~0.6MPa.

[0010] Furthermore, the surface roughness of the magnesium alloy substrate after sandblasting roughening treatment in step (1) is Ra0.8~6.3.

[0011] Furthermore, the cold spray coating in step (3) is a metal coating with a thickness of 0.1~1mm.

[0012] Furthermore, in step (3), when forming a cold spray coating on the surface of the magnesium alloy substrate, the cold spray powder material used is tantalum powder with a particle size distribution of 5~60 micrometers.

[0013] Furthermore, the laser cladding coating in step (4) is a nickel-based spherical porous alloy tungsten carbide coating with a thickness of 0.5~2mm.

[0014] Furthermore, during laser cladding in step (4), the overlap rate of the laser cladding passes is 30-60%;

[0015] The laser cladding coating is a mixture of nickel-based alloy and spherical porous alloy tungsten carbide powder, with a porosity of 5-60% and a particle size range of 5-100 micrometers for both the nickel-based alloy and the spherical porous alloy tungsten carbide.

[0016] Furthermore, the mass content of the spherical porous alloy tungsten carbide in the laser cladding coating is 10-60%, and the mass content of the alloy in the spherical porous alloy tungsten carbide is 6-20%.

[0017] Furthermore, the elemental composition of the nickel-based alloy in the laser cladding coating includes Ni, Cr, B, Si, C, and Fe elements;

[0018] The elemental composition of the spherical porous alloy tungsten carbide includes Ni, Cr, W and C.

[0019] Compared with the prior art, the technical solutions in the embodiments of the present invention have the following beneficial effects:

[0020] This invention first employs cold spraying to apply a metallic coating to the surface of a magnesium alloy. Then, a wear-resistant and corrosion-resistant coating is laser-clad. This effectively overcomes the difficulty of directly applying laser coatings to magnesium alloy surfaces. Furthermore, traditional dense, smooth alloy tungsten carbide or pure spherical tungsten carbide, due to their high density and smooth surface, tends to settle during the cladding process, thus deteriorating the performance of the cladding coating. This invention uses spherical porous alloy tungsten carbide powder, which has a rough surface and is lightweight, effectively preventing the settling effect during cladding. Additionally, the molten alloy binder phase during cladding effectively fills the pores of the spherical porous alloy tungsten carbide, resulting in a laser-clad layer with uniform hard phase distribution, high hardness, and high corrosion resistance, thus protecting the magnesium alloy substrate. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the double-layer coating on the magnesium alloy surface in an embodiment of the present invention.

[0022] Figure 2 This is a scanning electron microscope image of a spherical pure tungsten carbide cross-section.

[0023] Figure 3 This is a scanning electron microscope image showing the distribution of solid spherical tungsten carbide in the cladding layer.

[0024] Figure 4 This is a scanning electron microscope image of a spherical porous tungsten carbide.

[0025] Figure 5 This is a scanning electron microscope image showing the distribution of spherical porous tungsten carbide in the cladding layer.

[0026] Figure labeling: 1-Magnesium alloy; 2-Cold sprayed tantalum coating; 3-Clad layer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Example 1

[0029] A method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface includes the following steps:

[0030] (1) Use 60-mesh white corundum sand and sandblast roughen the surface of AZ31 magnesium alloy substrate under a pressure of 0.5MPa to remove its surface oxides and make the surface roughness of magnesium alloy substrate Ra3.2.

[0031] (2) Use acetone to clean the surface of the roughened magnesium alloy substrate in step (1) to remove oil stains;

[0032] (3) A tantalum coating with a thickness of 0.5 mm was sprayed on the surface of the magnesium alloy substrate using a high-pressure cold spraying process (spraying parameters: the pressure of the driving gas nitrogen was 5 MPa, the temperature was 800℃, the spraying distance was 30 mm, the angle between the spray gun and the spraying surface was 90°, and the powder feeding rate was 40 g / min).

[0033] The cold spray powder uses tantalum powder with a particle size distribution of 5-60 micrometers.

[0034] (4) A nickel-based spherical porous alloy tungsten carbide coating with a thickness of 0.3 mm is sprayed onto the surface of the tantalum layer cold-sprayed in step (3) using laser cladding process (laser power is 1500 W, laser scanning speed is 12 mm / s, spot diameter is 3.5 mm, coaxial powder feeding method is used with a powder feeding rate of 40 g / min, and argon protective gas flow rate is 6 L / min). The overlap rate between laser cladding passes is 40%.

[0035] During laser cladding, the laser cladding coating uses a mixture of nickel-based alloy and spherical porous alloy tungsten carbide powder with a particle size range of 5 to 100 micrometers and a porosity of 38%; among which, the mass content of the spherical porous alloy tungsten carbide is 14%.

[0036] The elemental composition and mass percentage of the nickel-based alloy in the laser cladding powder material are: Cr: 15%, B: 2.8%, Si: 4%, C: 0.6%, Fe: 4%, Ni: balance;

[0037] The elemental composition and mass percentage of the spherical porous alloy tungsten carbide are Ni: 10%, Cr: 4%, W: 80.8% and C: 5.2%.

[0038] like Figure 5 As shown, the spherical porous tungsten carbide is evenly distributed in the cladding layer, and the internal pores are filled with alloy. The corrosion resistance of the coated magnesium alloy is two orders of magnitude higher than that of AZ31 magnesium alloy, and the hardness is increased by 10 times.

[0039] Example 2

[0040] A method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface includes the following steps:

[0041] (1) Use 80-mesh white corundum sand and sandblast roughen the surface of WE43 magnesium alloy substrate under a pressure of 0.4MPa to remove its surface oxides and make the surface roughness of magnesium alloy substrate Ra3.0.

[0042] (2) Use acetone to clean the surface of the roughened magnesium alloy substrate in step (1) to remove oil stains;

[0043] (3) A tantalum coating with a thickness of 0.4 mm is sprayed onto the magnesium alloy substrate surface after the oil stains are removed in step (2) using a high-pressure cold spraying process (spraying parameters are: nitrogen pressure of driving gas is 4 MPa, temperature is 800℃, spraying distance is 30 mm, the angle between the spray gun and the spraying surface is 90°, and the powder feeding rate is 30 g / min).

[0044] The cold spray powder uses tantalum powder with a particle size distribution of 5-60 micrometers.

[0045] (4) A nickel-based spherical porous alloy tungsten carbide coating with a thickness of 0.3 mm is sprayed onto the surface of the tantalum layer cold-sprayed in step (3) using laser cladding process (laser power is 1300 W, laser scanning speed is 10 mm / s, spot diameter is 3 mm, coaxial powder feeding method is used with a powder feeding rate of 30 g / min, and argon protective gas flow rate is 6 L / min). The overlap rate between laser cladding passes is 45%.

[0046] During laser cladding, the laser cladding coating uses a mixture of nickel-based alloy and spherical porous alloy tungsten carbide powder with a particle size range of 5 to 100 micrometers and a porosity of 50%; wherein, the mass content of the spherical porous alloy tungsten carbide is 10%.

[0047] The elemental composition and mass percentage of the nickel-based alloy in the laser cladding powder material are: Cr: 13%, B: 2.5%, Si: 3.7%, C: 0.5%, Fe: 3.8%, Ni: balance;

[0048] The elemental composition and mass percentage of the spherical porous alloy tungsten carbide are Ni: 5%, Cr: 5%, W: 84.5% and C: 5.5%.

[0049] like Figure 5 As shown, the spherical porous tungsten carbide is evenly distributed in the cladding layer, and the internal pores are filled with alloy. The corrosion resistance of the coated magnesium alloy is two orders of magnitude higher than that of WE43 magnesium alloy, and the hardness is increased by 8 times.

[0050] Scanning electron microscope image of a spherical pure tungsten carbide cross section as shown below Figure 2 As shown, the scanning electron microscope image of the spherical porous tungsten carbide is as follows. Figure 4 As shown, Figure 3 This is a scanning electron microscope image of the distribution of solid spherical tungsten carbide in the cladding layer, from... Figure 3 It can be seen that the solid spherical tungsten carbide sinks to the bottom of the cladding layer and cannot effectively protect the magnesium alloy surface. Figure 5This is a scanning electron microscope image of the distribution of spherical porous tungsten carbide in the cladding layer, from... Figure 5 It can be seen that the spherical porous tungsten carbide is evenly distributed in the cladding layer, which can effectively protect the magnesium alloy substrate. The laser cladding layer on the surface of the magnesium alloy is more wear-resistant and has anti-corrosion function.

[0051] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface, characterized in that, Includes the following steps: (1) The surface of the magnesium alloy substrate is roughened by sandblasting; (2) The surface of the magnesium alloy substrate after sandblasting roughening in step (1) is degreased and cleaned; (3) A cold spray coating is formed on the surface of the magnesium alloy substrate after degreasing and cleaning in step (2) using a cold spray coating process. The cold spray coating is a tantalum coating, and the cold spray powder material used is tantalum powder. The particle size distribution of the tantalum powder is 5~60 micrometers, and the thickness of the cold spray coating is 0.1~1mm. (4) A laser cladding coating is applied to the surface of the magnesium alloy substrate with the cold spray coating in step (3). The laser cladding coating is a nickel-based spherical porous alloy tungsten carbide coating with a thickness of 0.5~2mm. The laser cladding coating is a mixed powder of nickel-based alloy and spherical porous alloy tungsten carbide, with a porosity of 5-60% and a particle size range of 5-100 micrometers for both the nickel-based alloy and the spherical porous alloy tungsten carbide. The mass content of the spherical porous alloy tungsten carbide in the laser cladding coating is 10-60%, and the mass content of the alloy in the spherical porous alloy tungsten carbide is 6-20%.

2. The method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface as described in claim 1, characterized in that, When performing sandblasting roughening treatment in step (1), white corundum sand with a particle size of 36~60 mesh is used, and the compressed air pressure used during sandblasting is 0.4~0.6MPa.

3. The method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface as described in claim 1, characterized in that, After sandblasting roughening treatment in step (1), the surface roughness of the magnesium alloy substrate is Ra 0.8~6.

3.

4. The method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface as described in claim 1, characterized in that, When laser cladding is performed in step (4), the overlap rate of the laser cladding passes is 30-60%.

5. The method for preparing an anti-corrosion and wear-resistant coating on a magnesium alloy surface as described in claim 1, characterized in that, The elemental composition of the nickel-based alloy in the laser cladding coating includes Ni, Cr, B, Si, C and Fe elements; The elemental composition of the spherical porous alloy tungsten carbide includes Ni, Cr, W and C.

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