A high wear-resistant and corrosion-resistant tungsten carbide coating on an alloy steel surface, and a preparation method and application thereof

Abstract

The application provides a high wear-resistant and corrosion-resistant tungsten carbide coating on an alloy steel surface and a preparation method and application thereof, and belongs to the technical field of wear-resistant and corrosion-resistant coatings. The application provides a high wear-resistant and corrosion-resistant tungsten carbide coating on an alloy steel surface, which is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; the HEAs is a BCC phase high-entropy alloy, the RE is a heavy rare earth oxide, and the Gr is a graphene nanosheet; x is 8-15wt%, y is 0.5-2.5wt%, and z is 0.5-1.5wt%. The results of the examples show that the relative density of the tungsten carbide coating is 97.9-99%, the fracture toughness is 13.5-15.5MPa·m 1 / 2 , the wear rate is 0.54-0.84×10 ‑6 mm 3 / Nm, and the corrosion current density is 1.04-1.32×10 ‑7 A / cm 2 .

Description

Technical Field

[0001] This invention relates to the field of wear-resistant and corrosion-resistant coating technology, and in particular to a high wear-resistant and corrosion-resistant tungsten carbide coating for alloy steel surfaces, its preparation method, and its application. Background Technology

[0002] Alloy steels, by adding alloying elements such as Cr, Ni, and Mo, can significantly improve their strength, hardness, and corrosion resistance, and are widely used in machinery manufacturing, bridges, and building steel structures. However, facing high-load or chloride-corrosion environments such as heavy-duty factories and coastal facilities, their overall performance still needs further improvement to meet the requirements of longer service life and lower maintenance.

[0003] Currently, many tungsten carbide (WC) cemented carbide coatings with excellent mechanical properties, wear resistance, and corrosion resistance, such as WC-Co, WC-Ni, and WC-Fe, are widely used for surface protection of mechanical parts. Among them, Co, Ni, and Fe act as binder phases, and their excellent wettability and adhesion enable them to bond tightly with the hard phase, thereby forming a robust integral structure.

[0004] To address increasingly complex operating environments, high-entropy alloys (HEAs) have been developed. These alloys consist of five or more main elements, each comprising between 5% and 35% of the total composition. In the field of traditional alloys, it is generally believed that increasing the number of main elements in an alloy often promotes the formation of intermetallic compounds, ultimately leading to increased brittleness. However, research shows that when multiple main elements are present in an alloy, the high-entropy effect can not only effectively inhibit the formation of intermetallic compounds but also promote the formation of solid solutions with face-centered cubic or body-centered cubic structures. These properties give high-entropy alloys excellent high-temperature resistance, corrosion resistance, wear resistance, and oxidation resistance, making them highly promising candidates to replace the binder phase in traditional cemented carbides.

[0005] However, with industrial development, the performance requirements for materials are becoming increasingly stringent, and the performance of composite coatings composed of carbides and high-entropy alloys is no longer sufficient to meet technical requirements. Therefore, how to further improve the wear and corrosion resistance of tungsten carbide coatings has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a high wear-resistant and corrosion-resistant tungsten carbide coating for alloy steel surfaces, its preparation method, and its application. The high wear-resistant and corrosion-resistant tungsten carbide coating provided by this invention has high density and high wear-resistant and corrosion-resistant properties.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a high wear-resistant and corrosion-resistant tungsten carbide coating for the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The HEAs are BCC phase high-entropy alloys; the RE are heavy rare earth oxides; and the Gr are graphene nanosheets. The x is 8~15wt%; the y is 0.5~2.5wt%; and the z is 0.5~1.5wt%.

[0008] Preferably, the HEAs are any one of FeCoNiCrAl, AlNbTiV, and AlCoCrFeNiSi.

[0009] Preferably, the RE is Yb2O3 and / or Er2O3.

[0010] This invention provides a method for preparing a high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of the alloy steel described in the above technical solution, comprising the following steps: (1) WC, high-entropy alloy powder, heavy rare earth oxide powder and graphene nanosheets were mixed and then reduced with hydrogen and nitrogen to obtain mixed powder; (2) The mixed powder obtained in step (1) is subjected to plasma spraying in an alternating magnetic field to obtain a coating; (3) The coating obtained in step (2) is heat-treated to obtain a high wear-resistant and corrosion-resistant tungsten carbide coating.

[0011] Preferably, in step (1), the temperature of hydrogen-nitrogen reduction is 300~400℃, the time of hydrogen-nitrogen reduction is 4~6h, and the gas for hydrogen-nitrogen reduction is a mixture of hydrogen and nitrogen, with a volume ratio of hydrogen to nitrogen of 1:(6~19).

[0012] Preferably, in step (1), the alternating magnetic field is generated by a magnetic field device, which uses an AC constant current source for output, and the output current of the magnetic field device is 0~60A and the output frequency of the magnetic field device is 20~120Hz.

[0013] Preferably, the substrate used for plasma spraying in step (2) is alloy steel; the substrate is polished, cleaned and preheated in sequence before plasma spraying.

[0014] Preferably, the protective gas for plasma spraying is an inert gas; the powder feeding gas for plasma spraying is an inert gas; the parameters of plasma spraying include: voltage 50~80V, current 500~600A, gas flow rate 100~240L / min, and powder feeding rate 300~400g / min.

[0015] Preferably, the heat treatment temperature in step (3) is 200~500℃ and the heat treatment time is 1~3h.

[0016] This invention provides the application of the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel as described in the above technical solution, or the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel prepared by the preparation method described in the above technical solution, in the fields of machinery manufacturing, bridge engineering, and construction.

[0017] This invention provides a high-wear-resistant and corrosion-resistant tungsten carbide coating for alloy steel surfaces. The high-wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; where HEAs is a BCC phase high-entropy alloy; RE is a heavy rare earth oxide; and Gr is graphene nanosheets; x is 8~15wt%; y is 0.5~2.5wt%; and z is 0.5~1.5wt%. This invention incorporates a small amount of heavy rare earth elements into the WC coating. This not only combines with impurities such as O to purify the substrate, but also increases the fluidity of the WC molten pool during spraying, reducing defects such as porosity and cracks in the coating and improving coating quality. Furthermore, it inhibits grain growth, resulting in finer grains, thereby increasing the material's hardness and strength. During the WC coating spraying process, the addition of heavy rare earth elements increases nucleation sites and forms rare earth oxide pinned grain boundaries, achieving grain refinement. While maintaining the high hardness and wear resistance of the WC coating, this also helps improve the coating's fracture toughness and corrosion resistance. Corrosion resistance; when graphene is incorporated into the binder phase as a reinforcing phase in WC coatings, it can significantly improve the matrix hardness. Graphene promotes the formation of a low-friction layer by improving the interfacial bonding strength between carbides in the binder phase; moreover, graphene's unique two-dimensional sheet structure can achieve grain refinement by restricting atomic diffusion paths, and dissolved graphene can generate a grain boundary pinning effect, effectively inhibiting grain boundary migration and abnormal grain growth; at the same time, graphene exhibits excellent structure during high-temperature spraying, and its anti-thermal decomposition properties ensure that it continues to play a functional strengthening role throughout the densification process; graphene is composed of carbon atoms arranged in sp... 2 The single-layer two-dimensional honeycomb lattice structure formed by tightly packed hybrid bonds has a lower coefficient of friction than graphite, making it an ideal building block for high-performance solid lubricants. Its unique interlayer slip properties and self-lubricating effect give it significant advantages in the field of friction-reducing coatings, making it a novel self-lubricating additive that effectively reduces friction and wear. The results of the embodiments show that the high wear-resistant and corrosion-resistant tungsten carbide coating provided by this invention has the following properties: relative density of 97.9~99%, and fracture toughness of 13.5~15.5 MPa·m. 1 / 2 The wear rate is 0.54~0.84×10. -6 mm 3 / Nm, corrosion current density is 1.04~1.32×10-7 A / cm 2 . Attached Figure Description

[0018] Figure 1 The metallographic structure of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1; Figure 2 The image shows the XRD pattern of the highly wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1. Figure 3 The friction and wear curve of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 is shown. Figure 4 The polarization curve of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 is shown. Figure 5 The metallographic structure of the tungsten carbide coating obtained in Comparative Example 1; Figure 6 The metallographic structure of the tungsten carbide coating obtained in Comparative Example 2 is shown. Detailed Implementation

[0019] This invention provides a high wear-resistant and corrosion-resistant tungsten carbide coating for the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The HEAs are BCC phase high-entropy alloys; the RE are heavy rare earth oxides; and the Gr are graphene nanosheets (GNPs). The x is 8~15wt%; the y is 0.5~2.5wt%; and the z is 0.5~1.5wt%.

[0020] In this invention, the HEAs are BCC phase high-entropy alloys, preferably any one of FeCoNiCrAl, AlNbTiV, and AlCoCrFeNiSi.

[0021] In this invention, the RE is a heavy rare earth oxide, preferably Yb2O3 and / or Er2O3.

[0022] In one embodiment of the present invention, x can be 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, or 15wt%; y can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, or 2.5wt%; and z can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, or 1.5wt%. The present invention optimizes the performance of a highly wear-resistant and corrosion-resistant tungsten carbide coating by adjusting the proportions of high-entropy alloys, heavy rare earth oxides, and graphene nanosheets.

[0023] This invention incorporates a small amount of heavy rare earth elements into the WC coating. These elements can combine with impurities such as O to purify the substrate, increase the fluidity of the WC molten pool during spraying, reduce defects such as porosity and cracks in the coating, and improve coating quality. Furthermore, they can inhibit grain growth, resulting in finer grains and thus improving the material's hardness and strength. During the WC coating spraying process, the addition of heavy rare earth elements increases nucleation sites and forms rare earth oxide pinned grain boundaries, achieving grain refinement. While ensuring the high hardness and wear resistance of the WC coating, this also helps to improve the coating's fracture toughness and corrosion resistance.

[0024] This invention significantly improves the matrix hardness when graphene is incorporated as a reinforcing phase into the binder phase of a WC coating. Graphene promotes the formation of a low-friction layer by improving the interfacial bonding strength between carbides in the binder phase. Furthermore, graphene's unique two-dimensional sheet structure can refine grains by restricting atomic diffusion paths, and dissolved graphene can generate a grain boundary pinning effect, effectively inhibiting grain boundary migration and abnormal grain growth. Simultaneously, graphene exhibits excellent structure during high-temperature spraying, and its resistance to thermal decomposition ensures continuous functional enhancement throughout the densification process. Graphene is composed of carbon atoms arranged in sp... 2 The single-layer two-dimensional honeycomb lattice structure formed by the close arrangement of hybrid bonds has a lower coefficient of friction than graphite, making it an ideal building block for high-performance solid lubricants. Its unique interlayer slip properties and self-lubricating effect give it significant advantages in the field of friction-reducing coatings, and it can be used as a new type of self-lubricating additive to effectively reduce friction and wear.

[0025] This invention also provides a method for preparing a high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of the alloy steel described in the above technical solution, comprising the following steps: (1) WC, high-entropy alloy powder, heavy rare earth oxide powder and graphene nanosheets were mixed and then reduced with hydrogen and nitrogen to obtain mixed powder; (2) The mixed powder obtained in step (1) is subjected to plasma spraying in an alternating magnetic field to obtain a coating; (3) The coating obtained in step (2) is heat-treated to obtain a high wear-resistant and corrosion-resistant tungsten carbide coating.

[0026] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0027] This invention involves mixing WC, high-entropy alloy powder, heavy rare earth oxide powder, and graphene nanosheets, followed by hydrogen-nitrogen reduction to obtain a mixed powder.

[0028] In this invention, the high-entropy alloy powder preferably includes any one of FeCoNiCrAl, AlNbTiV, and AlCoCrFeNiSi; the molar ratio of each element in the high-entropy alloy powder is preferably the same; the heavy rare earth oxide powder is preferably Yb2O3 powder and / or Er2O3 powder.

[0029] In this invention, based on a mass percentage of 100% for the mixed powder, the proportion of the high-entropy alloy powder is preferably 8-15%, the proportion of the heavy rare earth oxide powder is preferably 0.5-2.5%, and the proportion of the graphene nanosheets is preferably 0.5-1.5%. By controlling the amount of raw materials, this invention can obtain a highly wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel with a chemical composition that meets the requirements.

[0030] In this invention, the particle size of WC is preferably 75~95μm; the particle size of the high-entropy alloy powder is preferably 60~80μm; the particle size of the heavy rare earth oxide powder is preferably 5~10μm; and the size of the graphene nanosheets is preferably <10μm.

[0031] In this invention, the preferred method for mixing WC, high-entropy alloy powder, heavy rare earth oxide powder and graphene nanosheets is to perform wet milling, drying and grinding sequentially.

[0032] In this invention, the preferred rotational speed of the wet mill is 300-400 r / min; the preferred wet milling time is 12-24 h; the preferred medium used for the wet milling is anhydrous ethanol; and the preferred mass ratio of the grinding balls, anhydrous ethanol, and materials during the wet milling is 10:(0.5-2):(0.5-2), more preferably 10:1:1. This invention enables the components to be thoroughly and uniformly mixed through wet milling.

[0033] In this invention, the drying process includes preliminary drying and secondary drying.

[0034] In this invention, the vacuum degree of the preliminary drying is preferably 70-90 Pa; the temperature of the preliminary drying is preferably 70-90°C; and the preliminary drying is preferably carried out in a drying oven. This invention does not have a specific limitation on the preliminary drying time; based on the technical knowledge of those skilled in the art, it is sufficient to ensure that the raw material after wet milling is basically dry. This invention can remove anhydrous ethanol from the ball milling media used in wet milling through preliminary drying.

[0035] In this invention, the vacuum degree of the secondary drying is preferably 70~90 Pa; the temperature of the secondary drying is preferably 60~80℃; the time of the secondary drying is preferably 12~24 h; and the secondary drying is preferably carried out in a drying oven. This invention can further remove residual ball milling media through secondary drying.

[0036] The present invention does not impose any special limitations on the specific grinding operation. Based on the technical common sense of those skilled in the art, it can be determined that the raw materials can be fully dispersed.

[0037] In this invention, the preferred temperature for hydrogen-nitrogen reduction is 300-400°C; the preferred time for hydrogen-nitrogen reduction is 4-6 hours; the preferred gas for hydrogen-nitrogen reduction is a mixture of hydrogen and nitrogen; and the preferred volume ratio of hydrogen to nitrogen in the mixed gas is 1:(6-19). As one embodiment of this invention, the temperature for hydrogen-nitrogen reduction can be 300°C, 320°C, 340°C, 350°C, 360°C, 380°C, or 400°C; the preferred time for hydrogen-nitrogen reduction can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours; and the preferred volume ratio of hydrogen to nitrogen in the mixed gas can be 1:6, 1:8, 1:10, 1:12, 1:14, 1:15, 1:16, 1:18, or 1:19. This invention reduces the oxygen content of graphene nanosheets and improves powder purity through hydrogen-nitrogen reduction.

[0038] This invention does not impose any particular limitation on the cooling method for the hydrogen-nitrogen reduction; any method can be selected based on the technical knowledge of those skilled in the art. As one embodiment of this invention, the cooling method for hydrogen-nitrogen reduction can be to cool to 140-160°C and then cool to room temperature in the furnace. This invention, through furnace cooling, can remove internal stress in the powder.

[0039] After obtaining the mixed powder, the present invention performs plasma spraying on the mixed powder in an alternating magnetic field to obtain a coating.

[0040] In this invention, the alternating magnetic field is preferably generated by a magnetic field device; the magnetic field device preferably uses an AC constant current source output; the output current of the magnetic field device is preferably 0~60A; and the output frequency of the magnetic field device is preferably 20~120Hz. This invention can generate an alternating magnetic field through an induction coil by controlling the output current and frequency.

[0041] In this invention, the substrate used for plasma spraying is preferably alloy steel, more preferably Q345 steel; the substrate is preferably polished, cleaned and preheated in sequence before plasma spraying.

[0042] In this invention, the polishing is performed using sandpaper in stages. This invention does not impose any specific limitations on the polishing operation; based on the technical knowledge of those skilled in the art, the goal is simply to achieve a smooth surface on the substrate.

[0043] In this invention, the cleaning is preferably performed by ultrasonic cleaning in acetone and anhydrous ethanol for 10-20 minutes respectively. This invention does not impose any specific limitations on the power of the ultrasonic cleaning; based on the technical knowledge of those skilled in the art, it is sufficient to remove surface impurities.

[0044] In this invention, the preheating temperature is preferably 250~350℃, more preferably 300℃; the preheating time is preferably 1~3h, more preferably 2h. By preheating the substrate, this invention can avoid problems such as increased internal stress and cracking caused by excessively rapid cooling of the coating during subsequent plasma spraying.

[0045] In this invention, the substrate is preferably mounted on the worktable of the plasma spraying equipment during plasma spraying; the mixed powder is preferably fed into the powder feeder of the plasma spraying equipment.

[0046] In this invention, the distance between the substrate surface and the plasma spray gun during plasma spraying is preferably 6-10 cm, more preferably 7-9 cm, and even more preferably 8 cm.

[0047] The present invention preferably first activates the magnetic field device to generate an alternating magnetic field, then performs plasma spraying, and finally shuts off the magnetic field device after the plasma spraying is completed. Through the above operation, the present invention ensures that the plasma spraying process is conducted entirely within an alternating magnetic field.

[0048] In this invention, the protective gas for plasma spraying is preferably an inert gas, more preferably argon; the parameters of plasma spraying preferably include: voltage 50~80V, current 500~600A, gas flow rate 100~240L / min, and powder feeding rate 300~400g / min. In one embodiment of the present invention, the voltage can be 50V, 55V, 60V, 65V, 70V, 75V, or 80V; the current can be 500A, 510A, 520A, 530A, 540A, 550A, 560A, 570A, 580A, 590A, or 600A; the gas flow rate can be 100L / min, 120L / min, 140L / min, 160L / min, 180L / min, 200L / min, 220L / min, or 240L / min; and the powder feeding rate can be 300g / min, 320g / min, 340g / min, 360g / min, 380g / min, or 400g / min. The present invention does not impose a specific limitation on the plasma spraying time; it can be determined based on the technical knowledge of those skilled in the art, as long as the coating thickness meets the requirements.

[0049] In this invention, the thickness of the coating is preferably 20-35 mm, more preferably 25-30 mm. By controlling the coating thickness, this invention facilitates the subsequent acquisition of a high-wear-resistant and corrosion-resistant tungsten carbide coating with the required thickness.

[0050] After obtaining the coating, the present invention performs heat treatment on the coating to obtain a wear-resistant and corrosion-resistant tungsten carbide coating.

[0051] In this invention, the heat treatment temperature is preferably 200~500℃; the heat treatment time is preferably 1~3 hours; and the cooling method is preferably furnace cooling. As one embodiment of this invention, the heat treatment temperature can be 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, or 500℃; and the heat treatment time can be 2 hours. This invention eliminates internal stress in the coating through heat treatment.

[0052] In this invention, the thickness of the highly wear-resistant and corrosion-resistant tungsten carbide coating is preferably 20-35 mm, more preferably 25-30 mm. By controlling the thickness of the highly wear-resistant and corrosion-resistant tungsten carbide coating, this invention can further improve the protective ability of the highly wear-resistant and corrosion-resistant tungsten carbide coating on the substrate.

[0053] The preparation method provided by this invention is simple. By introducing an alternating magnetic field during the preparation process, a stirring effect of thermo-electromagnetic current can be provided during the deposition process, thereby eliminating defects in the coating, improving the density of the tungsten carbide coating, and thus improving the wear resistance and corrosion resistance of the tungsten carbide coating.

[0054] The present invention also provides the application of the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel as described in the above technical solution or the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel prepared by the preparation method described in the above technical solution in the fields of machinery manufacturing, bridge engineering and construction.

[0055] The present invention does not impose any special limitation on the specific method of application, and can be applied in a manner known to those skilled in the art.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] Example 1 A high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The Gr is graphene nanosheets, HEAs is FeCoNiCrAl (molar ratio of 1:1:1:1:1), and RE is Yb2O3; x is 8wt%, y is 0.5wt%, and z is 0.5wt%. The method for preparing the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of the alloy steel comprises the following steps: (1) WC, FeCoNiCrAl, Yb2O3 powder and graphene nanosheets were mixed and then subjected to wet milling, preliminary drying, secondary drying and grinding in sequence. Finally, the mixture was reduced with hydrogen and nitrogen at 300℃ for 4 hours, annealed at 150℃ and cooled to room temperature in the furnace to obtain a mixed powder. The wet milling speed was 350 r / min, the wet milling time was 24 hours, the medium used for wet milling was anhydrous ethanol, and the mass ratio of grinding balls, anhydrous ethanol and materials was 10:1:1. The vacuum degree of the preliminary drying was 85 Pa, the preliminary drying temperature was 90℃, and the initial drying temperature was 90℃. The initial drying is carried out in a drying oven, and then naturally cooled to room temperature after initial drying. The secondary drying is carried out in a drying oven with a vacuum degree of 70 Pa, a temperature of 65°C, and a time of 12 hours. The hydrogen-nitrogen reduction gas is a mixture of hydrogen and nitrogen with a volume ratio of 1:6. Based on the mass percentage of the mixed powder as 100%, WC accounts for 91%, high-entropy alloy powder accounts for 8%, heavy rare earth oxide powder accounts for 0.5%, and graphene nanosheets account for 0.5%. (2) The mixed powder obtained in step (1) is fed into the powder feeder of the plasma spraying equipment. Q345 steel with dimensions of 200mm×150mm×10mm is selected as the substrate. First, it is polished step by step with sandpaper, then ultrasonically cleaned with acetone and anhydrous ethanol for 20 minutes respectively. Then, it is preheated at 300℃ for 2 hours. Finally, the substrate is installed on the worktable of the plasma spraying equipment. The magnetic field device is used with AC constant current source output. The output current of the magnetic field device is 0~60 and the output frequency is 20~120Hz. An alternating magnetic field is generated in the plasma spraying equipment. Then, plasma spraying is carried out in the alternating magnetic field to obtain a coating with a thickness of 25mm. The distance between the substrate surface and the plasma spray gun during plasma spraying is 8cm. The plasma spraying method is multi-layer multi-pass spraying. The protective gas for plasma spraying is argon. The parameters of plasma spraying are: voltage 70V, current 580A, gas flow rate 220L / min, powder feeding amount 360g / min. (3) The coating obtained in step (2) is placed in a resistance furnace and heated to 300°C for 1 hour, and then cooled to room temperature with the furnace to obtain a high wear-resistant and corrosion-resistant tungsten carbide coating.

[0058] The thickness of the highly wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 is 25 mm.

[0059] Metallographic analysis was performed on the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the interface of the high wear-resistant and corrosion-resistant tungsten carbide coating is free of contamination and has good bonding, and the tungsten carbide is evenly distributed, and the porosity defects are also improved to a certain extent.

[0060] X-ray diffraction analysis was performed on the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1, and the XRD pattern is shown below. Figure 2 As shown. By Figure 2 It can be seen that the high wear-resistant and corrosion-resistant tungsten carbide coating contains WC, W2C, M7C3, and M. 23 C phase.

[0061] The relative density and fracture toughness of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 were tested. The relative density was measured using a solid density meter, and the actual density was calculated by comparing it with the theoretical density. The fracture toughness was measured using a Wilson 452SVD Vickers hardness tester with a load of 5 kg for 15 s. The fracture toughness was calculated using the Wilshwa formula, yielding a relative density of 98.1% and a fracture toughness of 13.5 MPa·m. 1 / 2 .

[0062] The friction coefficient of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 was tested. The test method was as follows: the wear behavior of the coating was measured using a QZ-301II multi-functional friction tester. The grinding ball was a Si3N4 alloy ball, the load was 15N, the sliding distance was 5mm, the frequency was 10Hz, and the wear time was 30min. The wear rate of the coating was then calculated, and the obtained friction and wear curve is shown below. Figure 3 As shown. By Figure 3 It can be seen that the average friction coefficient of the high wear-resistant and corrosion-resistant tungsten carbide coating is 0.36, and its wear rate is calculated to be 0.84 × 10⁻⁶. -6 mm 3 / Nm.

[0063] The corrosion resistance of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 1 was tested. The test method was as follows: the corrosion resistance of the coating was tested using an electrochemical workstation (CHI660E). The reference electrode was Ag-AgCl, the coating surface was the working electrode, and the platinum electrode was the auxiliary electrode. A potentiodynamic polarization test was performed in a 3.5 wt.% NaCl solution. The obtained polarization curve is shown below. Figure 4 As shown. Combined with Figure 4 The corrosion current density was calculated to be 1.32 × 10⁻⁶ using the Tafel extrapolation method. -7 A / cm 2 .

[0064] Example 2 A high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The Gr is graphene nanosheets, HEAs is FeCoNiCrAl (molar ratio of 1:1:1:1:1), and RE is Yb2O3; x is 10 wt%, y is 1 wt%, and z is 0.8 wt%. In step (1) of the method for preparing the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of the alloy steel, based on the mass percentage of the mixed powder as 100%, the proportion of WC is 88.2%, the proportion of high entropy alloy powder is 10%, the proportion of heavy rare earth oxide powder is 1%, and the proportion of graphene nanosheets is 0.8%. Other conditions are the same as in Example 1.

[0065] The performance of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 2 was tested, and the results were as follows: the relative density reached 97.9%, and the fracture toughness of the coating was 14.3 MPa·m. 1 / 2 The wear rate is 0.62 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 1.27×10 -7 A / cm 2 .

[0066] Example 3 A high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The Gr is graphene nanosheets, HEAs is FeCoNiCrAl (molar ratio of 1:1:1:1:1), and RE is Yb2O3; x is 12wt%, y is 1.5wt%, and z is 1wt%. In step (1) of the method for preparing the high wear-resistant and corrosion-resistant tungsten carbide coating, based on the mass percentage of the mixed powder as 100%, the proportion of WC is 85.5%, the proportion of high entropy alloy powder is 12%, the proportion of heavy rare earth oxide powder is 1.5%, and the proportion of graphene nanosheets is 1%. Other conditions are the same as in Example 1.

[0067] The performance of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 3 was tested, and the results were as follows: the relative density reached 98.4%, and the fracture toughness of the coating was 14.8 MPa·m. 1 / 2 The wear rate is 0.54 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 1.24×10 -7 A / cm 2 .

[0068] Comparative Example 1 A method for preparing a tungsten carbide coating comprises the following steps: (1) Based on the mass percentage of the mixed powder as 100%, the proportion of WC is 91.5%, the proportion of high entropy alloy powder is 8%, the proportion of heavy rare earth oxide powder is 0.5%, and other conditions are the same as step (1) of Example 1. (2) is the same as step (2) in Example 1; (3) is the same as step (3) in Example 1.

[0069] Metallographic analysis of the tungsten carbide coating obtained in Comparative Example 1 was performed, and the results are as follows: Figure 5 As shown. By Figure 5 It can be seen that there are obvious defects in the tungsten carbide coating, such as the aggregation of binder phase and coarse WC particles, which is caused by the lack of GNPs.

[0070] The properties of the tungsten carbide coating obtained in Comparative Example 1 were tested, and the results were as follows: relative density of 96.6% and fracture toughness of 13.1 MPa·m. 1 / 2 The wear rate is 3.34 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 3.26×10 -7 A / cm 2 It can be seen that, compared with Example 1, the absence of GNPs not only results in a decrease in coating density and fracture toughness, but also weakens grain boundary reinforcement and lubrication effects.

[0071] Comparative Example 2 A method for preparing a tungsten carbide coating comprises the following steps: (1) With the mass percentage of the mixed powder being 100%, the proportion of WC is 92% and the proportion of high-entropy alloy powder is 8%, and other conditions are the same as step (1) of Example 1; (2) is the same as step (2) in Example 1; (3) is the same as step (3) in Example 1.

[0072] Metallographic analysis of the tungsten carbide coating obtained in Comparative Example 2 was performed, and the results are as follows: Figure 6 As shown. The properties of the tungsten carbide coating obtained in Comparative Example 2 were tested, and the results were: relative density of 95.8% and fracture toughness of 12.8 MPa·m. 1 / 2 The wear rate was 4.58 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 4.69×10 -7 A / cm 2 .Depend on Figure 6The performance results show that, compared with Comparative Example 1, the absence of rare earth powder increases the porosity and cracks in the coating. Due to the lack of grain refinement and impurity purification, all properties of the coating show a downward trend.

[0073] Comparative Example 3 A method for preparing a tungsten carbide coating comprises the following steps: (1) WC, FeCoNiCrAl (molar ratio of 1:1:1:1:1), Yb2O3 powder and graphene nanosheets were mixed and then subjected to wet milling, preliminary drying, secondary drying and grinding in sequence. Finally, the mixture was reduced with hydrogen and nitrogen at 300℃ for 4 hours, annealed at 150℃ and cooled to room temperature in the furnace to obtain a mixed powder. The wet milling speed was 350 r / min, the wet milling time was 24 hours, the medium used for wet milling was anhydrous ethanol, and the mass ratio of grinding balls, anhydrous ethanol and materials during wet milling was 10:1:1. The vacuum degree of the preliminary drying was 85 Pa. The initial drying was carried out at 90℃ in a drying oven, followed by natural cooling to room temperature. The secondary drying was performed under a vacuum of 70Pa at 65℃ for 12 hours in a drying oven. The hydrogen-nitrogen reduction gas was a mixture of hydrogen and nitrogen with a volume ratio of 1:6. Based on a 100% mass percentage of the mixed powder, WC accounted for 88.2%, high-entropy alloy powder accounted for 10%, heavy rare earth oxide powder accounted for 1%, and graphene nanosheets accounted for 0.8%. (2) The mixed powder obtained in step (1) is fed into the powder feeder of the plasma spraying equipment. Q345 steel with dimensions of 200mm×150mm×10mm is selected as the substrate. First, it is polished step by step with sandpaper, then ultrasonically cleaned with acetone and anhydrous ethanol for 20 minutes respectively. Then, it is preheated at 300℃ for 2 hours. Finally, the substrate is installed on the worktable of the plasma spraying equipment, and then plasma spraying is performed to obtain a coating with a thickness of 25mm. The distance between the substrate surface and the plasma spray gun during plasma spraying is 8cm. The protective gas for plasma spraying is argon. The parameters of plasma spraying are: voltage 70V, current 580A, gas flow rate 220L / min, powder feeding amount 360g / min. (3) The coating obtained in step (2) is placed in a resistance furnace and heated to 300°C for 1 hour, and then cooled to room temperature with the furnace to obtain a tungsten carbide coating.

[0074] The properties of the tungsten carbide coating obtained in Comparative Example 3 were tested, and the results were as follows: relative density of 95.4% and fracture toughness of 13.2 MPa·m. 1 / 2 The wear rate is 3.26 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 3.52×10 -7 A / cm 2 As can be seen, compared with Example 2, due to the lack of magnetic field assistance, the stirring effect of thermo-electromagnetic current is lacking during the spraying process, resulting in more defects and poorer coating quality.

[0075] Example 4 A high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel, wherein the high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The Gr is graphene nanosheets, HEAs is FeCoNiCrAl (molar ratio of 1:1:1:1:1), and RE is Yb2O3; x is 12wt%, y is 2.5wt%, and z is 1.5wt%. The method for preparing the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of the alloy steel comprises the following steps: (1) WC, FeCoNiCrAl, Yb2O3 powders and graphene nanosheets were mixed and then subjected to wet milling, preliminary drying, secondary drying and grinding in sequence. Finally, the mixture was reduced with hydrogen and nitrogen at 300℃ for 4 hours, annealed at 150℃ and cooled to room temperature in the furnace to obtain a mixed powder. The wet milling speed was 350 r / min, the wet milling time was 24 hours, the medium used for wet milling was anhydrous ethanol, and the mass ratio of grinding balls, anhydrous ethanol and materials was 10:1:1. The vacuum degree of the preliminary drying was 85 Pa, the preliminary drying temperature was 90℃, and the preliminary drying process was carried out in a series of steps. The drying process is carried out in a drying oven, followed by natural cooling to room temperature. The secondary drying process is conducted under a vacuum of 70 Pa, at a temperature of 65°C, and for 12 hours, all within a drying oven. The hydrogen-nitrogen reduction gas is a mixture of hydrogen and nitrogen, with a volume ratio of 1:6. Based on a 100% mass percentage of the mixed powder, WC accounts for 84%, high-entropy alloy powder accounts for 12%, heavy rare earth oxide powder accounts for 2.5%, and graphene nanosheets account for 1.5%. (2) The mixed powder obtained in step (1) is fed into the powder feeder of the plasma spraying equipment. Q345 steel with dimensions of 200mm×150mm×10mm is selected as the substrate. First, it is polished step by step with sandpaper, then ultrasonically cleaned with acetone and anhydrous ethanol for 20min respectively. Then, it is preheated at 300℃ for 2h. Finally, the substrate is installed on the worktable of the plasma spraying equipment. The magnetic field device is used with AC constant current source output. The output current of the magnetic field device is 0~60 and the output frequency is 20~120Hz. An alternating magnetic field is generated in the plasma spraying equipment. Then, plasma spraying is carried out in the alternating magnetic field to obtain a coating with a thickness of 25mm. The distance between the substrate surface and the plasma spray gun during plasma spraying is 8cm. The protective gas for plasma spraying is argon. The parameters of plasma spraying are: voltage 70V, current 580A, gas flow rate 220L / min, powder feeding amount 360g / min. (3) The coating obtained in step (2) is placed in a resistance furnace and heated to 300°C for 1 hour, and then cooled to room temperature with the furnace to obtain a high wear-resistant and corrosion-resistant tungsten carbide coating.

[0076] The performance of the high wear-resistant and corrosion-resistant tungsten carbide coating obtained in Example 4 was tested, and the results were as follows: relative density of 98.8% and fracture toughness of 15.3 MPa·m. 1 / 2 The wear rate is 0.75 × 10⁻⁶. -6 mm 3 / Nm, corrosion current density is 1.44×10 -7 A / cm 2 .

[0077] The performance of the tungsten carbide coatings obtained in Examples 1-4 and Comparative Examples 1-3 was summarized, and the results are shown in Table 1: Table 1. Performance of the tungsten carbide coatings obtained in Examples 1-4 and Comparative Examples 1-3

[0078] As can be seen from Table 1, by introducing heavy rare earth elements and graphene into the coating and coating it under the action of an alternating magnetic field during the preparation process, the present invention can significantly improve the density of the coating and enhance its wear resistance and corrosion resistance.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of producing a high wear and corrosion resistant tungsten carbide coating on an alloy steel surface, characterized by, Includes the following steps: (1) WC, high-entropy alloy powder, heavy rare earth oxide powder and graphene nanosheets were mixed and then reduced with hydrogen and nitrogen to obtain mixed powder; (2) The mixed powder obtained in step (1) is subjected to plasma spraying in an alternating magnetic field to obtain a coating; (3) The coating obtained in step (2) is subjected to heat treatment to obtain a high wear-resistant and corrosion-resistant tungsten carbide coating; The high wear-resistant and corrosion-resistant tungsten carbide coating is a WC-x(HEAs)-y(RE)-z(Gr) composite coating; The HEAs are BCC phase high-entropy alloys; the RE are heavy rare earth oxides; and the Gr are graphene nanosheets. The x is 8~15wt%; the y is 0.5~2.5wt%; and the z is 0.5~1.5wt%.

2. The preparation method according to claim 1, characterized in that, In step (1), the temperature of hydrogen-nitrogen reduction is 300~400℃, the time of hydrogen-nitrogen reduction is 4~6h, and the gas for hydrogen-nitrogen reduction is a mixture of hydrogen and nitrogen, with a volume ratio of hydrogen to nitrogen of 1:(6~19).

3. The preparation method according to claim 1, characterized in that, In step (1), the alternating magnetic field is generated by a magnetic field device. The magnetic field device uses an AC constant current source for output. The output current of the magnetic field device is 0~60A and the output frequency of the magnetic field device is 20~120Hz.

4. The preparation method according to claim 1, characterized in that, In step (2), the substrate used for plasma spraying is alloy steel; the substrate is polished, cleaned and preheated in sequence before plasma spraying.

5. The preparation method according to claim 1, characterized in that, The protective gas for plasma spraying is an inert gas; the powder feeding gas for plasma spraying is an inert gas; the parameters of plasma spraying include: voltage 50~80V, current 500~600A, gas flow rate 100~240L / min, and powder feeding rate 300~400g / min.

6. The preparation method according to claim 1, characterized in that, The heat treatment temperature in step (3) is 200~500℃ and the heat treatment time is 1~3h.

7. The preparation method according to claim 1, characterized in that, The HEAs are any one of FeCoNiCrAl, AlNbTiV, and AlCoCrFeNiSi.

8. The preparation method according to claim 1, characterized in that, The RE is Yb2O3 and / or Er2O3.

9. The application of the high wear-resistant and corrosion-resistant tungsten carbide coating on the surface of alloy steel prepared by the preparation method according to any one of claims 1 to 8 in the fields of machinery manufacturing, bridge engineering and construction.

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