Titanium alloy laser surface cladding composite coating and preparation method thereof

Abstract

The invention relates to a preparation method of a titanium alloy laser surface cladding composite coating, which comprises the following steps: pretreating a titanium alloy base material to remove a surface oxide layer to obtain the treated titanium alloy base material; tungsten carbide powder is dried and evenly laid on the surface of the treated titanium alloy base material, and the titanium alloy base material with powder laid is obtained; carrying out surface laser treatment on the titanium alloy base material on which the powder is paved in a protective gas atmosphere to obtain a tungsten carbide / titanium alloy-based composite coating; the particle size of the tungsten carbide powder is 1-10 [mu] m. The tungsten carbide powder with the small particle size is adopted as a raw material, the tungsten carbide and a high-strength titanium alloy matrix are melted on the surface of the high-strength titanium alloy through a laser high-energy heat source, the metallurgical bonding effect is achieved, besides ceramic phase strengthening is achieved, the effect of fine crystal grains can be achieved, the fine crystal strengthening effect is achieved, and the hardness and abrasion resistance of the surface coating are improved. The surface hardness of the coating prepared through laser cladding of tungsten carbide on the surface of the titanium alloy is not lower than 60 HRC, and the wear rate is 3.6 * 10 <-4 > mm < 3 > N <-1 > m <-1 > or below.

Description

Technical Field

[0001] The invention belongs to the field of metal material surface engineering, and particularly relates to a titanium alloy laser surface cladding composite coating and a preparation method thereof. Background Art

[0002] The operating mechanism of the tank circuit breaker exhibits a significant and short-duration force peak during the driving process. This feature causes its transmission structure components, such as the piston rod and the sealing rod, to bear huge mechanical loads. In order to effectively reduce the power consumption required for system operation, high-strength titanium alloy materials are used to replace traditional 35CrMo steel. This not only achieves the lightweight of the equipment, but also significantly improves the overall stability of the tank circuit breaker during the driving process. However, it is worth noting that although titanium alloy has many advantages, its hardness is relatively low and its wear resistance is also lacking. When facing friction or wear service conditions during operation, the surface of the titanium alloy is easily damaged, which accelerates the wear process.

[0003] To address this issue, surface modification treatment is required for transmission components (including piston rods and sealing rods) made of titanium alloy to ensure their hardness meets or exceeds the standard of 60HRC. This measure aims to enhance the components' wear resistance and extend their service life, thereby ensuring the continuous and stable operation of tank circuit breakers and providing a solid guarantee for the safety and reliability of power systems.

[0004] Laser cladding technology is widely used in aerospace, automotive, and metallurgical industries. Compared to traditional surface treatment techniques, laser cladding offers greater efficiency and can significantly reduce maintenance time and manufacturing costs. During the cladding process, heating and cooling rates are extremely rapid, making it easy to obtain metastable phases such as amorphous alloys, thereby improving the performance of the cladding layer. The cladding layer forms a strong metallurgical bond with the substrate, resisting detachment. The cladding layer exhibits low dilution, minimally altering the substrate's properties, while significantly improving the surface's wear, corrosion, heat, oxidation, and electrical properties. A wide range of alloy systems can be clad, including self-fluxing alloy powders, carbide composite powders, and oxide ceramic powders. Laser cladding process parameters, including laser power, spot diameter, cladding speed, defocusing distance, powder feed rate, scanning speed, and preheating temperature, significantly influence the quality and performance of the cladding layer. Precise control of these process parameters can yield cladding layers with minimal dilution, dense microstructure, and excellent coating-substrate bonding.

[0005] Tungsten carbide titanium alloy coatings are usually prepared through advanced surface engineering technologies, such as laser cladding, supersonic flame spraying and other technologies. These technologies can heat tungsten carbide and titanium alloy powders to a molten or semi-molten state to form a dense coating. Tungsten carbide has excellent properties such as high hardness, high wear resistance, and high corrosion resistance, and is the main hardness component in the coating. Titanium alloy: It has the characteristics of high strength, low density, and good corrosion resistance. It is usually used as the substrate of the coating to improve the overall performance of the coating. The titanium alloy tungsten carbide composite coating prepared by laser cladding effectively protects the substrate during the operation of the tank circuit breaker and extends the service life of the component. However, the current laser cladding tungsten carbide titanium alloy coating still has problems such as uneven distribution of the strengthening phase, low microstructure density, and poor bonding between the coating and the substrate, resulting in low hardness and poor wear resistance of the titanium alloy coating.

[0006] In summary, in order to solve the problems of low hardness and poor wear resistance of titanium alloy coatings, a better preparation method needs to be developed. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a titanium alloy surface laser cladding composite coating, comprising the following steps:

[0008] Pre-treating the titanium alloy substrate to remove the surface oxide layer to obtain a treated titanium alloy substrate;

[0009] drying the tungsten carbide powder and evenly spreading it on the surface of the treated titanium alloy substrate to obtain a powdered titanium alloy substrate;

[0010] performing a surface laser treatment on the powdered titanium alloy substrate under a protective gas atmosphere to obtain a tungsten carbide / titanium alloy-based composite coating;

[0011] The particle size of the tungsten carbide powder is 1 to 10 μm.

[0012] Preferably, the laser power of the laser treatment process is 1-5 kW, the scanning speed is 720-1080 mm / min, and the spot diameter is 5-8 mm.

[0013] Preferably, the laser power of the laser processing process is 2-4 kW.

[0014] Preferably, the particle size of the tungsten carbide powder is 3 to 7 μm.

[0015] Preferably, the overlap rate between lanes during the laser processing is 30% to 50%.

[0016] Preferably, the protective gas is argon, and the oxygen content in the molding environment is kept no higher than 100 ppm.

[0017] Preferably, the pretreatment specifically includes: grinding the surface of the substrate with a grinding wheel and sandpaper to remove the oxide layer.

[0018] Preferably, the pretreatment further comprises: after removing the oxide layer, cleaning the surface with acetone or ethanol and then placing it in an oven at a temperature of 150-180° C. for 2-4 hours.

[0019] Preferably, the drying of the tungsten carbide powder specifically includes: placing the tungsten carbide powder in a vacuum oven for drying at a temperature of 120 to 150° C. for 4 to 6 hours.

[0020] Based on the same inventive concept, the present invention also provides a titanium alloy laser surface cladding composite coating, which is prepared using the titanium alloy laser surface cladding composite coating preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention proposes a preparation method of a titanium alloy laser surface cladding composite coating, which comprises pre-treating a titanium alloy substrate to remove a surface oxide layer to obtain a treated titanium alloy substrate; drying tungsten carbide powder and evenly laying it on the surface of the treated titanium alloy substrate to obtain a powdered titanium alloy substrate; performing surface laser treatment on the powdered titanium alloy substrate under a protective gas atmosphere to obtain a tungsten carbide / titanium alloy-based composite coating; the particle size of the tungsten carbide powder is 1 to 10 μm. The present invention uses small-particle tungsten carbide powder as raw material, and uses a laser high-energy heat source to melt tungsten carbide and a high-strength titanium alloy matrix on the surface of a high-strength titanium alloy to achieve a metallurgical bonding effect. In addition to strengthening the ceramic phase, it can also refine the grains to achieve a fine grain strengthening effect, thereby improving the hardness and wear resistance of the surface coating. The coating obtained by laser cladding tungsten carbide on the titanium alloy surface has a surface hardness of not less than 60HRC and a wear rate of 3.6×10 -4 mm 3 N -1 m -1 In addition, the preparation method proposed by the present invention has a simple processing flow and is suitable for large-scale promotion and industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a microstructure diagram of the tungsten carbide / titanium alloy-based composite coating of Example 1 of the present invention;

[0024] Figure 2 This is a microstructure diagram of the tungsten carbide / titanium alloy-based composite coating of Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] Tungsten carbide powder with a particle size of 5 μm was dried in a vacuum oven at 135°C for 5 hours. The substrate was a Ti55511 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe). The surface was polished with a grinding wheel and sandpaper to remove the oxide layer. The surface was then cleaned with acetone or ethanol and placed in an oven at 165°C for 3 hours.

[0028] Titanium alloy composite coatings were prepared using a powder spreading method. First, oven-dried tungsten carbide powder was evenly spread on the titanium alloy surface. Laser power was 3kW, scanning speed was 900mm / min, spot diameter was 6mm, and the overlap ratio was 40%. Argon was used as a shielding gas to prevent oxidation, maintaining the oxygen content in the molding environment below 100ppm. The tungsten carbide / titanium alloy-based composite coating was then formed.

[0029] After the composite coating is prepared, it is cut using an electric spark wire cutting device perpendicular to the laser scanning direction, and the coating structure is observed using a scanning electron microscope (e.g. Figure 1 ), and the coating was mechanically tested with a hardness tester, and the hardness of the composite coating was 62HRC.

[0030] Example 2

[0031] Tungsten carbide powder with a particle size of 7 μm was dried in a vacuum oven at 120°C for 4 hours. The substrate, made of Ti55511 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe), was polished using a grinding wheel and sandpaper to remove the oxide layer. The surface was then cleaned with acetone or ethanol and placed in an oven at 150°C for 2 hours.

[0032] Titanium alloy composite coatings were prepared using a powder spreading method. First, oven-dried tungsten carbide powder was evenly spread on the titanium alloy surface. Laser power was 2kW, scanning speed was 1080mm / min, spot diameter was 5mm, and overlap ratio was 30%. Argon was used as a shielding gas to prevent oxidation, maintaining an oxygen content of no more than 100ppm in the molding environment. The tungsten carbide / titanium alloy-based composite coating was then formed.

[0033] After the composite coating is prepared, it is cut using an electric spark wire cutting device perpendicular to the laser scanning direction, and the coating structure is observed using a scanning electron microscope (e.g. Figure 2 ), and the coating was mechanically tested with a hardness tester, and the hardness of the composite coating was 65HRC.

[0034] Example 3

[0035] Tungsten carbide powder with a particle size of 3 μm was dried in a vacuum oven at 150°C for 6 hours. The substrate, made of Ti55511 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe), was polished using a grinding wheel and sandpaper to remove the oxide layer. The surface was then cleaned with acetone or ethanol and placed in an oven at 180°C for 4 hours.

[0036] A titanium alloy composite coating was prepared using a more user-friendly powder spreading method. First, oven-dried tungsten carbide powder was evenly spread on the titanium alloy surface. Laser power was 5kW, scanning speed was 720mm / min, spot diameter was 8mm, and the overlap ratio was 50%. Argon was used as a shielding gas to prevent oxidation, maintaining an oxygen content of no more than 100ppm in the molding environment. The tungsten carbide / titanium alloy-based composite coating was then formed.

[0037] After the composite coating is prepared, it is cut using an electric spark wire cutting device perpendicular to the laser scanning direction, and the coating is mechanically tested using a hardness tester. The composite hardness is 61HRC.

[0038] Example 4

[0039] Tungsten carbide powder with a particle size of 5 μm was dried in a vacuum oven at 140°C for 6 hours. The substrate, made of Ti55511 titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe), was polished using a grinding wheel and sandpaper to remove the oxide layer. The surface was then cleaned with acetone or ethanol and placed in an oven at 170°C for 4 hours.

[0040] A more user-friendly powder spreading method was used to prepare titanium alloy composite coatings. First, oven-dried tungsten carbide powder was evenly spread on the titanium alloy surface. Laser power was 1-5kW, scanning speed 810mm / min, spot diameter 7mm, and inter-pass overlap ratio 30%. Argon was used as a shielding gas to prevent oxidation, maintaining the oxygen content in the molding environment below 100ppm. The tungsten carbide / titanium alloy-based composite coating was prepared.

[0041] After the composite coating is prepared, it is cut using an electric spark wire cutting device perpendicular to the laser scanning direction, and the coating is mechanically tested using a hardness tester. The hardness of the composite coating is 63HRC.

[0042] Examples 5 to 10

[0043] The preparation methods of the composite coatings of Examples 5 to 10 are substantially the same as those of Example 1, with the differences being shown in Table 1.

[0044] Table 1 Differences in process parameters

[0045]

[0046] The composite coatings prepared in Examples 5 to 10 were cut using a wire-cut electric discharge device perpendicular to the laser scanning direction, and the coatings were mechanically tested using a hardness tester. The hardness of the composite coatings was above 60 HRC.

[0047] Comparative Example 1

[0048] The Ti55511 titanium alloy substrate was polished with a grinding wheel and sandpaper to remove the oxide layer. The surface was cleaned with acetone or ethanol and then placed in an oven at 150°C for 2 hours.

[0049] A laser remelting method was used for comparison. The laser power was 3kW, the scanning speed was 900mm / min, the spot diameter was 6mm, and the overlap ratio was 40%. Argon was used as a shielding gas to prevent oxidation and maintain the oxygen content in the molding environment below 100ppm to produce the laser remelted surface.

[0050] After preparation, the specimen was processed using wire-cut EDM equipment, and the remelted area was tested using a hardness tester. The test result was 38 HRC, compared to the base material hardness of 33 HRC.

[0051] Reciprocating sliding wear tests were conducted on the polished samples obtained in Examples 1-4 and Comparative Example 1, along with a titanium alloy substrate, at a sliding speed of 0.01 m / s, a stroke length of 5 mm, and an applied load of 50 N for 3600 seconds. Al2O3 ceramic balls served as the friction pair. The test results are summarized in Table 2.

[0052] Table 2 Summary of performance of examples and comparative examples

[0053]

[0054] By comparing the embodiment with comparative example 1, it can be seen that the hardness of the tungsten carbide titanium alloy composite coating prepared by laser cladding is above 60HRC, and the wear rate is 3.6×10 -4 mm 3 N -1 m -1 The hardness of the examples shown below is significantly higher than that of the WC-free Ti5553 remelted layer in the comparative example, which only reached 38 HRC. The composite coatings offer improved wear resistance compared to the original titanium alloy surface, and their hardness meets the requirements for service life under working conditions. The remelted layer's higher hardness compared to the substrate is due to the rapid cooling of laser remelting, resulting in fine grains and increased hardness.

[0055] From the comparison of Examples 1 and 2, it can be seen that the hardness obtained in Example 2 with a small heat input is higher and the wear rate is lower. This is because less tungsten carbide melts during the cladding process and more is retained. Figure 1 、 2It can also be seen from the comparison that in the composite coating of Example 2, the tungsten carbide is more evenly distributed.

[0056] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for preparing a titanium alloy surface laser cladding composite coating, characterized in that: The following steps are involved: Pre-treating the titanium alloy substrate to remove the surface oxide layer to obtain a treated titanium alloy substrate; drying the tungsten carbide powder and evenly spreading it on the surface of the treated titanium alloy substrate to obtain a powdered titanium alloy substrate; performing a surface laser treatment on the powdered titanium alloy substrate under a protective gas atmosphere to obtain a tungsten carbide / titanium alloy-based composite coating; The particle size of the tungsten carbide powder is 1 to 10 μm.

2. The preparation method according to claim 1, characterized in that The laser power of the laser treatment process is 1-5 kW, the scanning speed is 720-1080 mm / min, and the spot diameter is 5-8 mm.

3. The preparation method according to claim 2, characterized in that The laser power of the laser processing process is 2-4 kW.

4. The preparation method according to claim 1, characterized in that The particle size of the tungsten carbide powder is 3 to 7 μm.

5. The preparation method according to claim 1, characterized in that The overlap rate between paths in the laser processing process is 30% to 50%.

6. The preparation method according to claim 1, characterized in that The protective gas is argon, and the oxygen content in the molding environment is kept below 100 ppm.

7. The preparation method according to claim 1, characterized in that The pretreatment specifically includes: using a grinding wheel and sandpaper to grind the surface of the substrate to remove the oxide layer.

8. The preparation method according to claim 7, characterized in that The pretreatment further comprises: after removing the oxide layer, cleaning the surface with acetone or ethanol and then placing the product in an oven at a temperature of 150-180° C. for 2-4 hours.

9. The preparation method according to claim 1, characterized in that The drying of the tungsten carbide powder specifically includes: placing the tungsten carbide powder in a vacuum oven for drying at a temperature of 120 to 150° C. for 4 to 6 hours.

10. A titanium alloy laser surface cladding composite coating, characterized in that: The titanium alloy laser surface cladding composite coating is prepared by the preparation method according to any one of claims 1 to 9.

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