A nano-wc reinforced ni-ti erosion resistant coating and a method of making the same

Abstract

The application provides a nano WC reinforced NiTi wear-resistant and cavitation-resistant coating and a preparation method thereof, and the method comprises the following steps: selecting nano WC powder, cleaning and drying the nano WC powder, adding an ethanol solution of a silane coupling agent to the nano WC powder for a modification reaction to obtain modified nano WC powder; performing gradient mixing on B2 phase NiTi intermetallic compound powder and the modified nano WC powder, and performing mechanical alloying on the mixture by using a refrigeration ball milling process to obtain NiTi / nano WC composite powder; and spraying the NiTi / nano WC composite powder on the surface of a target substrate by using an AC-HVAF thermal spraying process to form a nano WC reinforced NiTi wear-resistant and cavitation-resistant coating on the surface of the target substrate. The method solves the technical problems that the existing water turbine over-flow component coating cannot simultaneously achieve the anti-wear and anti-cavitation performance, the NiTi coating has low bonding strength and is easy to be oxidized, and the nano WC is easy to be aggregated; and the prepared coating has the anti-cavitation performance and high wear-resistant characteristics, has high interface bonding strength and high density.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering coating preparation technology, specifically relating to a nano-WC reinforced NiTi wear-resistant coating and its preparation method. Background Technology

[0002] In the service environment of multiphase flow machinery such as solid-liquid flow equipment, the flow components are often eroded by solid particles in the fluid, leading to metal loss. This causes vibration and noise during operation, resulting in low operating efficiency, frequent overhauls, and shortened service life, seriously affecting the stability and safety of equipment operation. In fluid machinery, erosion is the result of the combined effects of scouring, wear, and cavitation. These three phenomena coexist and promote each other, jointly leading to erosion damage in fluid machinery.

[0003] In the protection of fluid machinery, methods such as applying polyurethane, polyethylene coatings, and thermal spraying to apply wear-resistant coatings are widely used to resist abrasion damage. However, non-metallic anti-abrasion materials have short service life due to their low bonding strength. Thermal spray coatings, such as welded NiCrBSi coatings and high-velocity flaming (HVOF) WC-Co coatings, have also been widely used. However, thermally sprayed hard coatings only perform well in terms of small-angle impact erosion and wear resistance. When subjected to near-90° impacts at the inlet edge of fluid machinery runners, the protective effect is not significant, and may even be inferior to the base material. In particular, they lack the function of resisting cavitation damage. For example, damage to HVOF-sprayed WC coatings due to cavitation is often observed on the negative pressure side of the outlet blades of mixed-flow turbines. Its actual cavitation resistance is slightly lower than that of martensitic stainless steel. The inability to unify wear resistance and cavitation resistance in fluid machinery surface coatings makes cavitation damage an unavoidable form of damage in fluid machinery.

[0004] NiTi coatings exhibit high resistance to cavitation erosion. The principle behind this is that during the impact of cavitation bubble collapse, the NiTi alloy undergoes a martensitic phase transformation under impact stress. During this transformation, it absorbs the energy generated by cavitation, thus resisting cavitation erosion. B2 phase NiTi alloys demonstrate superior cavitation erosion resistance compared to martensitic NiTi alloys. Extensive cavitation erosion testing has shown that the cavitation volume loss of NiTi alloys is significantly lower than that of the base material.

[0005] Tungsten carbide (WC) is a ceramic material with high hardness and wear resistance. Nano-WC particles exhibit even higher hardness and wear resistance, a large specific surface area and strong interfacial bonding ability, and a more significant dispersion strengthening effect in composite coatings. Therefore, this invention proposes to mechanically alloy nano-WC hard particles and NiTi alloy powder to prepare a nano-NiTi / WC composite coating. Based on composite material theory, the coating will possess the cavitation erosion resistance of NiTi alloy while exhibiting higher erosion wear resistance than a single NiTi alloy. However, the technical challenges in reinforcing the NiTi coating with nano-WC hard particles include achieving a good bond between the nano-WC hard particles and the shape-memory effect of the NiTi alloy, while retaining the NiTi alloy's ability to absorb energy during impact deformation, and reducing the low bonding strength and easy oxidation of the NiTi coating, as well as the tendency of nano-WC to agglomerate. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art, and provides a nano-WC-reinforced NiTi wear-resistant coating and its preparation method.

[0007] One aspect of the present invention provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, the method comprising: Step 1: Select nano WC powder, clean and dry the nano WC powder, add silane coupling agent ethanol solution to carry out modification reaction, and obtain modified nano WC powder. Step 2: The B2 phase NiTi intermetallic compound powder and the modified nano WC powder are gradient mixed and mechanically alloyed using a cold ball milling process to obtain NiTi / nano WC composite powder. Step 3: The dried NiTi / nano WC composite powder is sprayed onto the surface of the target substrate using the AC-HVAF thermal spraying process to form a nano WC-reinforced NiTi wear-resistant coating on the surface of the target substrate.

[0008] Optionally, in step two, the B2 phase NiTi intermetallic compound powder and the modified nano-WC powder are subjected to gradient mixing, including: The B2 phase NiTi intermetallic compound powder was placed in a ball mill jar, and then the modified nano WC powder was added to the ball mill jar in multiple batches for ball milling; wherein the B2 phase NiTi intermetallic compound powder and the modified nano WC powder were mixed in a gradient at a volume ratio of 95:5 to 60:40.

[0009] Optionally, during the ball milling process, the ball-to-material ratio is controlled at 15:1 to 20:1, argon gas is introduced into the ball mill jar as a protective gas, the ball milling speed is set to 250 r / min to 300 r / min, the ball milling time is set to 8 h to 12 h, and the ball milling chamber temperature is set to -20℃ to 0℃.

[0010] Optionally, the modified nano-WC powder is added to a ball mill jar in multiple batches for ball milling, including: The nano WC powder was added to the ball mill jar in three batches at 30%, 40%, and 30% of the target addition amount for ball milling.

[0011] Optionally, in step one, the nano WC powder is ultrasonically cleaned with anhydrous ethanol, wherein the ultrasonic cleaning power is 300~400W and the cleaning time is 15~20min. The mass fraction of silane coupling agent in the ethanol solution is 3%~5%, the modification reaction temperature is 60℃~70℃, and the modification reaction time is 2h~3h.

[0012] Optionally, in step one, the cleaned nano-WC powder is dried, including: The cleaned nano WC powder was placed in a vacuum drying oven and dried at a temperature range of 80℃~90℃ for 4h~6h.

[0013] Optionally, the parameters for the AC-HVAF thermal spraying process in step three are: the spraying fuel is propane, and the propane flow rate is 1.2 m³ / s. 3 / h ~1.5m 3 / h, oxygen flow rate 3.5 m 3 / h ~4.0 m 3 / h, the carrier gas is nitrogen, and the carrier gas flow rate is 0.8 m³ / h. 3 / h ~1.0m 3 / h, spraying distance 180 mm~220 mm, powder feeding rate 30 g / min ~40 g / min, spray gun moving speed 300 mm / s ~400 mm / s.

[0014] Optionally, in step one, the nano WC powder selected includes: nano WC powder with a particle size of 50 nm to 80 nm and a purity of ≥99.5%; The particle size range of the B2 phase NiTi intermetallic compound powder mentioned in step two is 50μm ~ 100μm, and the purity is ≥ 99.5%.

[0015] Optionally, in step three, during the AC-HVAF thermal spraying process, the target substrate is cooled by water cooling, and the temperature of the target substrate is controlled below 80℃.

[0016] Another aspect of the present invention provides a nano-WC-reinforced NiTi wear-resistant coating, which is prepared by the method described above for preparing nano-WC-reinforced NiTi wear-resistant coatings.

[0017] This invention provides a nano-WC-reinforced NiTi wear-resistant coating and its preparation method. In this method, the surface of nano-WC is modified using a silane coupling agent, effectively reducing its surface energy and suppressing agglomeration during ball milling and spraying. This also improves the interfacial compatibility between nano-WC and the NiTi matrix, preventing interfacial gaps from becoming sources of wear crack initiation. B2-phase NiTi intermetallic compound powder is gradient-mixed with the modified nano-WC powder and mechanically alloyed using a cold ball milling process, further achieving uniform dispersion of nano-WC in the NiTi matrix and ensuring the compositional uniformity of the composite powder. The NiTi / nano-WC composite powder is sprayed onto the target substrate surface using an AC-HVAF thermal spraying process to form a nano-WC-reinforced NiTi wear-resistant coating. This thermal spraying process features low heat input and high spraying speed. Precisely controlled spraying process parameters effectively suppress oxidation and unexpected phase transformation of NiTi powder during deposition, solving the problems of severe oxidation and unstable chemical composition in traditional thermally sprayed NiTi coatings.

[0018] The method for preparing nano-WC-reinforced NiTi wear-resistant coating provided by this invention has clear process parameters and is feasible to operate. Each step is adapted to the requirements of industrial production. The composite powder preparation and thermal spraying processes are easy to control and can achieve large-scale protection of components such as turbine flow parts. At the same time, this method can also be extended to the surface protection of other fluid machinery equipment subjected to coupled abrasion, and has broad application prospects. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart illustrating a method for preparing a nano-WC-reinforced NiTi wear-resistant coating according to an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, one aspect of the present invention provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, the method comprising: Step 1: Select nano WC powder, clean and dry the nano WC powder, add silane coupling agent ethanol solution to carry out modification reaction, and obtain modified nano WC powder.

[0022] Specifically, nano-WC powder with a particle size of 50nm~80nm and a purity of ≥99.5% is selected. The selected nano-WC powder is placed in anhydrous ethanol and ultrasonically cleaned at a power of 300W~400W for 15min~20min to remove impurities and oxide layers from the powder surface. Then, the cleaned nano-WC powder is placed in a vacuum drying oven and dried at a temperature range of 80℃~90℃ for 4h~6h to obtain pretreated nano-WC powder.

[0023] Among these features, nano-sized WC powder provides an ultra-large specific surface area and dispersion enhancement effect; high-purity WC powder avoids interfacial embrittlement or decreased corrosion resistance caused by impurities. The nano-WC powder is dried in a vacuum environment to avoid high-temperature oxidation. This combination of drying temperature and time thoroughly removes residual solvent without damaging the grafted layer of the silane coupling agent, ensuring the storage stability of the modified nano-WC and its dispersion performance during subsequent ball milling.

[0024] In this embodiment, the silane coupling agent is KH560. A KH560 silane coupling agent ethanol solution was prepared at a mass fraction of 3%–5%. Pretreated nano-WC powder was added to the silane coupling agent ethanol solution, and the mixture was stirred and reacted in a water bath at 60°C–70°C for 2–3 hours to allow KH560 to be fully grafted onto the surface of the nano-WC powder, reducing its surface energy and preventing agglomeration. After the reaction, the mixture was centrifuged at 8000–10000 r / min for 10–15 minutes, the supernatant was removed, and the precipitate was placed in a vacuum drying oven and dried at 80°C–90°C for 4–6 hours to obtain modified nano-WC powder.

[0025] Among them, moderate ultrasonic intensity and time can effectively remove impurities on the surface of nano WC without damaging the particles; KH560 can be fully grafted onto the WC surface at this concentration and temperature, minimizing its surface energy, inhibiting agglomeration from the source, and improving the interfacial compatibility between WC and NiTi matrix.

[0026] In this embodiment, KH560 silane coupling agent is used to modify the surface of nano-WC, which effectively reduces the surface energy of nano-WC and inhibits its agglomeration during ball milling and spraying from the source. At the same time, it improves the interfacial compatibility between nano-WC and NiTi matrix, and avoids the interfacial gap from becoming the source of erosion crack initiation.

[0027] Step 2: The B2 phase NiTi intermetallic compound powder and the modified nano WC powder are mixed in a gradient and mechanically alloyed using a cold ball milling process to obtain NiTi / nano WC composite powder.

[0028] Specifically, B2 phase NiTi intermetallic compound powder with a particle size of 50μm~100μm and a purity of ≥99.5% was selected as the matrix phase. The micron-sized B2 phase NiTi as the matrix phase ensures depositability during the spraying process; the high purity of the B2 phase NiTi intermetallic compound powder avoids interface embrittlement or decreased corrosion resistance caused by the introduction of impurities.

[0029] The B2 phase NiTi intermetallic compound powder was placed in a ball mill jar, and then the modified nano-WC powder was added to the ball mill jar in multiple batches for ball milling to avoid agglomeration and uneven dispersion caused by adding the modified nano-WC powder all at once. The B2 phase NiTi intermetallic compound powder and the modified nano-WC powder were mixed in a gradient at a volume ratio of 95:5 to 60:40.

[0030] Compared to one-time mixing, this feeding sequence and ratio range can effectively suppress the agglomeration tendency of nano WC powder in the early stage of ball milling, while ensuring the macroscopic uniformity of WC distribution in the composite powder, laying the compositional foundation for obtaining a low porosity and high density coating in the future.

[0031] Preferably, the B2 phase NiTi intermetallic compound powder is placed in a ball mill jar, and then the nano-WC powder is added in three batches at 30%, 40%, and 30% of the target addition amount for ball milling. This batch feeding method avoids agglomeration caused by excessively high instantaneous local concentrations, ensuring that each batch of WC powder is promptly coated and dispersed by the NiTi powder during ball milling. This is the most crucial step in achieving gradient mixing and directly guarantees the compositional uniformity of the composite powder.

[0032] The mechanical alloying process using refrigerated ball milling specifically includes: adding the mixed powder into the grinding jar of a planetary refrigerated ball mill; using stainless steel grinding balls; controlling the ball-to-powder ratio at 15:1 to 20:1 during grinding; and introducing argon gas into the grinding jar as a protective gas to prevent powder oxidation during grinding. The grinding speed is set to 250 r / min to 300 r / min, the grinding time to 8 h to 12 h, and the grinding chamber temperature to -20℃ to 0℃. Low temperature is used to suppress plastic deformation of the NiTi powder while ensuring that the nano-sized WC properties are not lost. After grinding, the resulting composite powder is placed in a vacuum drying oven and dried at 100℃ to 110℃ for 2 h to 3 h to obtain NiTi / nano-WC composite powder. In this powder, the nano-WC is uniformly dispersed in the NiTi matrix without significant agglomeration.

[0033] Among them, the low-temperature grinding environment inhibits the plastic deformation and adhesion of NiTi powder, and avoids the loss of WC nano-properties; argon protection prevents powder oxidation; the optimized ball-to-powder ratio, rotation speed and time combination ensures the uniform dispersion of nano-WC in the NiTi matrix without over-grinding or agglomeration.

[0034] Step 3: The dried NiTi / nano WC composite powder is sprayed onto the surface of the target substrate using the AC-HVAF thermal spraying process to form a nano WC-reinforced NiTi wear-resistant coating on the surface of the target substrate.

[0035] Specifically, in this embodiment, the target substrate is selected from 0Cr13Ni5Mo stainless steel commonly used in turbine flow components. The target substrate surface is first pretreated by sandblasting with 80-100 mesh white corundum sand at a pressure of 0.5-0.6 MPa and an angle of 70-80° until the surface roughness of the substrate reaches Ra15-20 μm. This removes the oxide scale and oil stains on the substrate surface and improves the adhesion between the coating and the substrate. After sandblasting, the substrate surface is cleaned with anhydrous ethanol and dried for later use.

[0036] NiTi / nano WC composite powder is added to the powder feeder of the AC-HVAF thermal spraying equipment. The composite coating is prepared on the pretreated target substrate surface using the AC-HVAF thermal spraying process. During the spraying process, water cooling is used to cool the substrate and control the substrate temperature below 80℃ to prevent the substrate from deforming due to heat. At the same time, excessive thermal stress is avoided at the interface between the coating and the substrate due to the difference in thermal expansion coefficients, thus ensuring high interfacial bonding strength between the coating and the substrate.

[0037] The parameters for the AC-HVAF thermal spraying process are as follows: the spraying fuel is propane, and the propane flow rate is 1.2 m³ / s. 3 / h ~1.5m 3 / h, oxygen flow rate 3.5 m 3 / h ~4.0 m 3 / h, the carrier gas is nitrogen, and the carrier gas flow rate is 0.8 m³ / h. 3 / h ~1.0 m 3 The spraying speed is 30 g / min to 40 g / min, the spray gun moving speed is 300 mm / s to 400 mm / s. By precisely controlling the heat input and particle flight speed, the oxidation and unexpected phase transformation of NiTi powder during the spraying process are suppressed, while ensuring that the composite powder particles collide with the substrate at high speed to form a dense coating.

[0038] The present invention provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating. This method modifies the surface of nano-WC using a silane coupling agent, effectively reducing the surface energy of the nano-WC and suppressing its agglomeration during ball milling and spraying. Simultaneously, it improves the interfacial compatibility between the nano-WC and the NiTi matrix, preventing interfacial gaps from becoming sources of wear crack initiation. A gradient mixing process is performed between B2-phase NiTi intermetallic compound powder and the modified nano-WC powder, followed by mechanical alloying using a cold ball milling process. This further achieves uniform dispersion of nano-WC in the NiTi matrix, ensuring the compositional uniformity of the composite powder. The NiTi / nano-WC composite powder is then sprayed onto the target substrate surface using an AC-HVAF thermal spraying process to form a nano-WC-reinforced NiTi wear-resistant coating. This thermal spraying process features low heat input and high spraying speed. Precisely controlled spraying process parameters effectively suppress oxidation and unexpected phase transformation of the NiTi powder during deposition, solving the problems of severe oxidation and unstable chemical composition in traditional thermally sprayed NiTi coatings.

[0039] The method for preparing nano-WC-reinforced NiTi wear-resistant coating provided by this invention has clear process parameters and is feasible to operate. Each step is adapted to the requirements of industrial production. The composite powder preparation and thermal spraying processes are easy to control and can achieve large-scale protection of components such as turbine flow parts. At the same time, this method can also be extended to the surface protection of other fluid machinery equipment subjected to coupled abrasion, and has broad application prospects.

[0040] Another aspect of the present invention provides a nano-WC-reinforced NiTi wear-resistant coating, which is prepared using the method described above. The specific process of preparing this nano-WC-reinforced NiTi wear-resistant coating has been described in detail above and will not be repeated here.

[0041] The present invention prepares a nano-WC-reinforced NiTi wear-resistant coating with a coating thickness controlled at 200μm~300μm, a coating porosity ≤1%, an interfacial bonding strength ≥50MPa, and a microhardness of 450HV~650HV, exhibiting both excellent wear resistance and cavitation erosion resistance.

[0042] The nano-WC-reinforced NiTi wear-resistant coating prepared by this invention fully utilizes the energy absorption effect of the martensitic phase transformation of NiTi alloy and the hardening effect of nano-WC to achieve a synergistic unity of wear resistance and cavitation erosion resistance. The coating porosity is ≤1%, the interfacial bonding strength is ≥50MPa, the cavitation erosion volume loss is reduced by more than 60% compared with 0Cr13Ni5Mo stainless steel, and the wear rate is reduced by more than 50% compared with pure NiTi coating. It exhibits excellent comprehensive protective performance under coupled erosion-wear-cavitation erosion conditions.

[0043] The following examples illustrate the specific process of preparing the nano-WC-reinforced NiTi wear-resistant coating provided by this invention.

[0044] Example 1 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 60nm and a purity of 99.6%, place it in anhydrous ethanol and ultrasonically clean it at 350W for 18min, then vacuum dry it at 85℃ for 5h; prepare a 4% KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 65℃ water bath for 2.5h, centrifuge at 9000r / min for 12min, and vacuum dry it at 85℃ for 5h to obtain modified nano-WC powder.

[0045] Step 2: Select B2 phase NiTi powder with a particle size of 80μm and a purity of 99.6%, and mix it with modified nano-WC powder at a volume ratio of 90:10. Add the nano-WC powder in three batches (30%, 40%, and 30%) to a ball mill jar for ball milling. The ball-to-material ratio is 18:1. Use stainless steel grinding balls, argon protection, and a cooling ball milling speed of 280 r / min for 10 h. The ball milling chamber temperature is -10℃. After ball milling, vacuum dry at 105℃ for 2.5 h to obtain composite powder.

[0046] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 90-mesh white corundum sand at a pressure of 0.55 MPa to achieve a surface roughness of Ra 15 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF with a propane flow rate of 1.3 m³ / h. 3 / h, oxygen flow rate is 3.8 m 3 / h, nitrogen carrier gas flow rate is 0.9 m 3 The spraying distance is 200mm, the powder feeding rate is 35g / min, the spray gun moving speed is 350mm / s, and the water-cooled temperature-controlled substrate temperature is ≤80℃.

[0047] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 250 μm, a porosity of 0.8%, an interfacial bonding strength of 55 MPa, a microhardness of 500 HV, and a cavitation volume loss that is 65% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 55% lower than that of pure NiTi coating.

[0048] Example 2 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 50nm and a purity of 99.5%, place it in anhydrous ethanol and ultrasonically clean it at 300W for 20min, then vacuum dry it at 80℃ for 6h; prepare a 3% mass fraction KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 60℃ water bath for 3h, centrifuge at 8000r / min for 15min, and vacuum dry it at 80℃ for 6h to obtain modified nano-WC powder.

[0049] Step 2: Select B2 phase NiTi powder with a particle size of 50μm and a purity of 99.5%, and mix it with modified nano-WC powder at a volume ratio of 70:30. Add the nano-WC powder to the ball mill jar in three batches at a target addition amount of 30%, 40%, and 30% for ball milling. The ball-to-material ratio is 15:1. Use stainless steel grinding balls, argon protection, and a cooling ball milling speed of 250 r / min. The ball milling time is 12 h, and the ball milling chamber temperature is 0℃. After ball milling, vacuum dry at 100℃ for 3 h to obtain composite powder.

[0050] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 80-mesh white corundum sand at a pressure of 0.5 MPa to achieve a surface roughness of Ra 15 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF at a propane flow rate of 1.2 m³ / h. 3 / h, oxygen flow rate is 3.5 m 3 / h, nitrogen carrier gas flow rate is 0.8 m 3 / h, spraying distance is 180mm, powder feeding rate is 30g / min, spray gun moving speed is 300mm / s, and water-cooled temperature-controlled substrate temperature is ≤80℃.

[0051] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 200 μm, a porosity of 0.7%, an interfacial bonding strength of 52 MPa, a microhardness of 600 HV, and a cavitation volume loss that is 70% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 60% lower than that of pure NiTi coating.

[0052] Example 3 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 80nm and a purity of 99.7%, place it in anhydrous ethanol and ultrasonically clean it at 400W for 15min, then vacuum dry it at 90℃ for 4h; prepare a 5% mass fraction KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 70℃ water bath for 2h, centrifuge at 10000r / min for 10min, and vacuum dry it at 90℃ for 4h to obtain modified nano-WC powder.

[0053] Step 2: Select B2 phase NiTi powder with a particle size of 100μm and a purity of 99.7%, and mix it with modified nano-WC powder at a volume ratio of 60:40. Add the nano-WC powder to the ball mill jar in three batches at 30%, 40%, and 30% of the target addition amount for ball milling. The ball-to-material ratio is 20:1. Stainless steel grinding balls are used, argon gas is used for protection, the ball milling speed is 300 r / min, the ball milling time is 8 h, and the ball milling chamber temperature is -20℃. After ball milling, vacuum dry at 110℃ for 2 h to obtain composite powder.

[0054] Step 3: Select 0Cr13Ni5Mo stainless steel as the target substrate, and sandblast it with 100-mesh white corundum sand at a sandblasting pressure of 0.6MPa to achieve a surface roughness of Ra20μm. Clean and dry with anhydrous ethanol. The composite powder is then thermally sprayed using AC-HVAF with a propane flow rate of 1.5m³ / h, an oxygen flow rate of 4.0m³ / h, a nitrogen carrier gas flow rate of 1.0m³ / h, a spraying distance of 220mm, a powder feeding rate of 40g / min, a spray gun moving speed of 400mm / s, and a water-cooled temperature-controlled substrate temperature ≤80℃.

[0055] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 300 μm, a porosity of 0.9%, an interfacial bonding strength of 58 MPa, a microhardness of 650 HV, and a cavitation volume loss that is 68% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 58% lower than that of pure NiTi coating.

[0056] Example 4 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 50nm and a purity of 99.5%, place it in anhydrous ethanol and ultrasonically clean it at 300W for 15min, then vacuum dry it at 80℃ for 4h; prepare a 3% KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 60℃ water bath for 2h, centrifuge at 8000r / min for 10min, and vacuum dry it at 80℃ for 4h to obtain modified nano-WC powder.

[0057] Step 2: Select B2 phase NiTi powder with a particle size of 50μm and a purity of 99.5%, and mix it with modified nano-WC powder at a volume ratio of 95:5. Add the nano-WC powder in three batches (30%, 40%, and 30%) to a ball mill jar for ball milling. The ball-to-material ratio is 15:1. Use stainless steel grinding balls, argon protection, and a cooling ball milling speed of 250 r / min for 8 hours. The ball milling chamber temperature is -20℃. After ball milling, vacuum dry at 100℃ for 2 hours to obtain the composite powder.

[0058] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 80-mesh white corundum sand at a pressure of 0.5 MPa to achieve a surface roughness of Ra 15 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF at a propane flow rate of 1.2 m³ / h. 3 / h, oxygen flow rate is 3.5 m 3 / h, nitrogen carrier gas flow rate is 0.8 m 3 / h, spraying distance is 180mm, powder feeding rate is 30g / min, spray gun moving speed is 300mm / s, and water-cooled temperature-controlled substrate temperature is ≤80℃.

[0059] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 200 μm, a porosity of 0.6%, an interfacial bonding strength of 50 MPa, a microhardness of 450 HV, and a cavitation volume loss that is 62% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 52% lower than that of pure NiTi coating.

[0060] Example 5 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 80nm and a purity of 99.7%, place it in anhydrous ethanol and ultrasonically clean it at 400W for 20min, then vacuum dry it at 90℃ for 6h; prepare a 5% mass fraction KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 70℃ water bath for 3h, centrifuge at 10000r / min for 15min, and vacuum dry it at 90℃ for 6h to obtain modified nano-WC powder.

[0061] Step 2: Select B2 phase NiTi powder with a particle size of 100μm and a purity of 99.7%, and mix it with modified nano-WC powder at a volume ratio of 60:40. Add the nano-WC powder in three batches (30%, 40%, and 30%) to a ball mill jar for ball milling. The ball-to-material ratio is 20:1. Use stainless steel grinding balls, argon protection, and a cooling ball milling speed of 300 r / min for 12 h. The ball milling chamber temperature is 0℃. After ball milling, vacuum dry at 110℃ for 3 h to obtain composite powder.

[0062] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 100-mesh white corundum sand at a pressure of 0.6 MPa to achieve a surface roughness of Ra 20 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF with a propane flow rate of 1.5 m³ / h. 3 / h, oxygen flow rate is 4.0 m 3 / h, nitrogen carrier gas flow rate is 1.0 m³ / h. 3 / h, spraying distance is 220mm, powder feeding rate is 40g / min, spray gun moving speed is 400mm / s, and water-cooled temperature-controlled substrate temperature is ≤80℃.

[0063] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 300 μm, a porosity of 0.9%, an interfacial bonding strength of 58 MPa, a microhardness of 650 HV, and a cavitation volume loss that is 66% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 56% lower than that of pure NiTi coating.

[0064] Example 6 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 65nm and a purity of 99.6%, place it in anhydrous ethanol and ultrasonically clean it at 350W for 18min, then vacuum dry it at 85℃ for 5h; prepare a 4% KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a 65℃ water bath for 2.5h, centrifuge at 9000r / min for 13min, and vacuum dry it at 85℃ for 5h to obtain modified nano-WC powder.

[0065] Step 2: Select B2 phase NiTi powder with a particle size of 75μm and a purity of 99.6%, and mix it with modified nano-WC powder at a volume ratio of 80:20. Add the nano-WC powder in three batches (30%, 40%, and 30%) to a ball mill jar for ball milling. The ball-to-material ratio is 18:1. Stainless steel grinding balls are used, with argon protection, a cooling ball milling speed of 275 r / min, a ball milling time of 10 h, and a ball milling chamber temperature of -10℃. After ball milling, vacuum dry at 105℃ for 2.5 h to obtain composite powder.

[0066] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 90-mesh white corundum sand at a pressure of 0.55 MPa to achieve a surface roughness of Ra 18 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF with a propane flow rate of 1.35 m³ / h. 3 / h, oxygen flow rate is 3.75 m 3 / h, nitrogen carrier gas flow rate is 0.9 m 3 The spraying distance is 200mm, the powder feeding rate is 35g / min, the spray gun moving speed is 350mm / s, and the water-cooled temperature-controlled substrate temperature is ≤80℃.

[0067] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 250 μm, a porosity of 0.7%, an interfacial bonding strength of 54 MPa, a microhardness of 550 HV, and a cavitation volume loss that is 68% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 58% lower than that of pure NiTi coating.

[0068] Example 7 This embodiment provides a method for preparing a nano-WC-reinforced NiTi wear-resistant coating, comprising the following steps: Step 1: Select nano-WC powder with a particle size of 55nm and a purity of 99.5%, place it in anhydrous ethanol and ultrasonically clean it at 320W for 16min, then vacuum dry it at 82℃ for 4.5h; prepare a 3.5% KH560 silane coupling agent ethanol solution, add the pretreated nano-WC powder, stir and react in a water bath at 62℃ for 2.2h, centrifuge at 8500r / min for 11min, and vacuum dry it at 82℃ for 4.5h to obtain modified nano-WC powder.

[0069] Step 2: Select B2 phase NiTi powder with a particle size of 60μm and a purity of 99.5%, and mix it with modified nano-WC powder at a volume ratio of 85:15. Add the nano-WC powder in three batches (30%, 40%, and 30%) to a ball mill jar for ball milling. The ball-to-material ratio is 16:1. Stainless steel grinding balls are used, with argon protection, a cooling ball milling speed of 260 r / min, a ball milling time of 9 h, and a ball milling chamber temperature of -5℃. After ball milling, vacuum dry at 102℃ for 2.2 h to obtain composite powder.

[0070] Step 3: 0Cr13Ni5Mo stainless steel was selected as the target substrate and sandblasted with 85-mesh white corundum sand at a pressure of 0.52 MPa to achieve a surface roughness of Ra 16 μm. The substrate was then cleaned and dried with anhydrous ethanol. The composite powder was then thermally sprayed using AC-HVAF with a propane flow rate of 1.25 m³ / h. 3 / h, oxygen flow rate is 3.6 m 3 / h, nitrogen carrier gas flow rate is 0.85 m³ / h. 3 / h, spraying distance is 190mm, powder feeding rate is 32g / min, spray gun moving speed is 320mm / s, and water-cooled temperature-controlled substrate temperature is ≤80℃.

[0071] The prepared nano-WC reinforced NiTi wear-resistant coating has a thickness of 230 μm, a porosity of 0.75%, an interfacial bonding strength of 53 MPa, a microhardness of 520 HV, and a cavitation volume loss that is 66% lower than that of 0Cr13Ni5Mo stainless steel, and a wear rate that is 56% lower than that of pure NiTi coating.

[0072] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a nano-WC-reinforced NiTi wear-resistant coating, characterized in that, The preparation method includes: Step 1: Select nano WC powder, clean and dry the nano WC powder, add silane coupling agent ethanol solution to carry out modification reaction, and obtain modified nano WC powder. Step 2: The B2 phase NiTi intermetallic compound powder and the modified nano WC powder are gradient mixed and mechanically alloyed using a cold ball milling process to obtain NiTi / nano WC composite powder. Step 3: The dried NiTi / nano WC composite powder is sprayed onto the surface of the target substrate using the AC-HVAF thermal spraying process to form a nano WC-reinforced NiTi wear-resistant coating on the surface of the target substrate.

2. The preparation method according to claim 1, characterized in that, Step two involves gradient mixing of the B2 phase NiTi intermetallic compound powder and the modified nano-WC powder, including: The B2 phase NiTi intermetallic compound powder was placed in a ball mill jar, and then the modified nano WC powder was added to the ball mill jar in multiple batches for ball milling; wherein the B2 phase NiTi intermetallic compound powder and the modified nano WC powder were mixed in a gradient at a volume ratio of 95:5 to 60:

40.

3. The preparation method according to claim 2, characterized in that, During the ball milling process, the ball-to-material ratio is controlled at 15:1 to 20:

1. Argon gas is introduced into the ball mill jar as a protective gas. The ball milling speed is set to 250 r / min to 300 r / min, the ball milling time is set to 8 h to 12 h, and the ball milling chamber temperature is set to -20℃ to 0℃.

4. The preparation method according to claim 2, characterized in that, The modified nano-WC powder was added to a ball mill jar in multiple batches for ball milling, including: The nano WC powder was added to the ball mill jar in three batches at 30%, 40%, and 30% of the target addition amount for ball milling.

5. The preparation method according to claim 1, characterized in that, In step one, the nano WC powder is ultrasonically cleaned with anhydrous ethanol, wherein the ultrasonic cleaning power is 300~400W and the cleaning time is 15~20min; The mass fraction of silane coupling agent in the ethanol solution is 3%~5%, the modification reaction temperature is 60℃~70℃, and the modification reaction time is 2h~3h.

6. The preparation method according to claim 1, characterized in that, Step one involves drying the cleaned nano-WC powder, including: The cleaned nano WC powder was placed in a vacuum drying oven and dried at a temperature range of 80℃~90℃ for 4h~6h.

7. The preparation method according to claim 1, characterized in that, The parameters for the AC-HVAF thermal spraying process used in step three are as follows: the spraying fuel is propane, and the propane flow rate is 1.2 m³ / s. 3 / h ~1.5m 3 / h, oxygen flow rate 3.5 m 3 / h ~4.0 m 3 / h, the carrier gas is nitrogen, and the carrier gas flow rate is 0.8 m³ / h. 3 / h ~1.0 m 3 / h, spraying distance 180 mm~220 mm, powder feeding rate 30 g / min~40 g / min, spray gun moving speed 300 mm / s~400 mm / s.

8. The preparation method according to claim 1, characterized in that, Step 1 involves selecting nano-WC powder, including nano-WC powder with a particle size of 50 nm to 80 nm and a purity of ≥99.5%. The particle size range of the B2 phase NiTi intermetallic compound powder mentioned in step two is 50μm ~ 100μm, and the purity is ≥ 99.5%.

9. The preparation method according to claim 1, characterized in that, In step three, during the AC-HVAF thermal spraying process, the target substrate is cooled by water, and the temperature of the target substrate is controlled below 80℃.

10. A nano-WC-reinforced NiTi wear-resistant coating, characterized in that, The nano-WC-reinforced NiTi wear-resistant coating is prepared using the preparation method described in any one of claims 1 to 9.

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