Medium-entropy (Zr, Ta, W) C coating and preparation method and application thereof

Abstract

The invention discloses a medium-entropy (Zr, Ta, W) C coating and a preparation method and application thereof. The medium-entropy (Zr, Ta, W) C gradient coating is prepared on the surface of the titanium alloy or the iron-based alloy through the double-layer glow plasma surface metallurgy technology, and gradient temperature annealing treatment is conducted. The preparation method has the specific advantages that (1) the prepared coating is of a continuous gradient structure, good interface metallurgical bonding is formed between the coating and a matrix, the bonding force of the coating is not lower than 50 N, and the coating is not prone to cracking and stripping in the service process due to the high bonding strength; and (2) the hardness of the medium-entropy (Zr, Ta, W) C coating prepared by the method is 25-30 GPa, the fracture toughness is 4.0-5.0 MPa * m < 1 / 2 >, and the coating system has balanced hardness and toughness, so that the coating is endowed with excellent wear resistance. The prepared coating has excellent wear resistance and antifriction performance, and has wide application prospects in the field of wear-resistant protective coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wear-resistant protective coating, in particular to a medium-entropy (Zr, Ta, W)C coating and a preparation method and application thereof. BACKGROUND

[0002] In many fields of modern industrial production and scientific research, high requirements are put forward for the wear resistance and lubrication performance of material surface. For example, in the field of aerospace, although the commonly used titanium alloy has the advantages of high strength and low density, the high-temperature components inside the engine need to withstand strong mechanical friction and thermal stress under high-speed operation and extreme temperature environment. The insufficient wear resistance and lubrication performance of titanium alloy will greatly affect the performance and reliability of the engine, and even endanger the safety of flight. In the field of mechanical manufacturing, various cutting tools and transmission components are long-term under high-load friction working conditions. The traditional iron-based alloy materials do not have good wear resistance and lubrication performance, and a large amount of friction heat is easily generated, which reduces the service life of the tool. A good wear-resistant and lubricating coating can significantly improve the service life of the tool, reduce the maintenance cost of the equipment, and improve the production efficiency.

[0003] At present, a variety of wear-resistant coating systems have been developed. For example, some ceramic materials have the characteristics of low density, high hardness and high wear resistance, and are often used as protective coatings for low wear-resistant alloy materials. For example, TaC has excellent wear resistance and thermal conductivity, and TaC coating can significantly improve the wear resistance of the material surface. WC is one of the highest known carbides (hardness about 2000 HV), which can effectively resist abrasive wear, and WC coating has good lubrication performance, which can significantly improve the service life of the coating. However, the coating system composed of a single or a small number of elements gradually encounters a bottleneck in performance improvement. In contrast, the multi-component system exhibits more excellent comprehensive performance, such as better mechanical properties and higher stability, which provides a new direction for the development of coating materials.

[0004] In recent years, high-entropy coatings or multi-component coatings have attracted widespread attention due to their unique high-entropy effect and excellent performance. However, in the actual preparation process, there are many challenges. Traditional coating preparation methods, such as atmospheric plasma spraying (APS) and electron beam physical vapor deposition (EB-PVD), have difficulty in achieving uniform distribution of multiple component elements when preparing high-entropy coatings, resulting in low bonding force between the coating and the substrate, which affects the service life of the coating. Moreover, the preparation of high-entropy coatings is difficult, and some conventional methods have high requirements for equipment, complex process and high cost in the preparation process, which is not conducive to large-scale production and application. At present, there is a lack of an efficient, stable and high-quality coating preparation method for high-entropy or multi-component coatings. This has great significance for promoting the wide application of high-entropy coatings in practical engineering. SUMMARY

[0005] The present application aims to solve the problems of poor wear resistance and lubrication of titanium alloy materials and iron-based alloy materials, and provides a medium-entropy (Zr, Ta, W) C coating, a preparation method and application thereof, which significantly improves the wear resistance and lubrication of the material. Meanwhile, a gradient structure with metallurgical bonding is formed between the coating and the substrate, ensuring the bonding strength between the coating and the substrate, largely avoiding problems such as cracks and even peeling of the coating during preparation and service, and prolonging the service life of the coating.

[0006] To solve the problems in the prior art, the technical scheme adopted by the present application is:

[0007] A medium-entropy (Zr, Ta, W) C coating, the medium-entropy coating comprising the following components by mass fraction: ZrC 35% to 45%, TaC 35% to 45%, WC 10% to 30%, and the total amount being 100%; the medium-entropy (Zr, Ta, W) C coating is a gradient composite coating, comprising a substrate, a diffusion layer, and a deposition layer from bottom to top; the main components of the deposition layer material are ZrC, TaC, and WC, atoms in the substrate material diffuse to the deposition layer, Zr atoms, Ta atoms, W atoms, and C atoms in the deposition layer diffuse to the substrate material, forming metallurgical bonding between the deposition layer and the substrate material, and forming a diffusion layer at the interface between the deposition layer and the substrate; the hardness is 25 to 30 GPa, and the fracture toughness is 4.0 to 5.0 MPa*m 1 / 2 , the wear rate under 15-minute room temperature and 8N load is less than 4*10 -6 mm 3 N -1 m -1 .

[0008] Preferably, the material of the substrate is a titanium alloy material or an iron-based alloy material.

[0009] The preparation method of the above-mentioned medium-entropy (Zr, Ta, W) C coating comprises the following steps:

[0010] (1) Substrate surface treatment

[0011] Wipe and clean the chamber of the double-glow plasma surface metallurgy equipment furnace body with sandpaper and alcohol, fix the physically polished substrate material on the sample piece table, adjust the distance between the upper surface of the substrate and the target material (the distance between the poles), close the chamber, and after the vacuum degree is drawn to 0.1 Pa, introduce protective gas argon, and the chamber gas pressure is kept below 40 Pa; use the Ar + plasma in the double-layer glow plasma surface metallurgy equipment to perform ion bombardment cleaning on the upper surface of the substrate;

[0012] (2) Gradient coating preparation

[0013] After cleaning, adjust the workpiece current, target material current and chamber pressure of the double glow plasma surface metallurgy equipment to prepare a coating on the upper surface of the substrate; after the heat preservation is completed, start the double glow furnace cooling work, and the cooling time is not less than 1.5 h; the cooling is achieved by reducing the target material current and the workpiece current; when the temperature is reduced to room temperature, the sample is taken out of the double glow furnace and placed in anhydrous ethanol for ultrasonic cleaning, and is ready for use;

[0014] (3) Gradient temperature annealing

[0015] Put the sample into the crucible, then slowly place the crucible with the sample in the center of the furnace tube constant temperature zone, seal the furnace tube, and then pump the vacuum degree to 0.1 Pa, and then introduce Ar gas as the protective gas; set the furnace program, the first stage: make the temperature rise from room temperature to the annealing low temperature stage, and keep warm; the second stage: continue to rise to the annealing high temperature stage, and keep warm; after the heat preservation is completed, turn off the heating power, let the sample cool down with the furnace, keep the vacuum state to cool down to room temperature, then slowly release the gas to the normal pressure, and take out the sample.

[0016] Preferably, the physical polishing and polishing in step (1) refers to polishing the upper surface of the substrate material sample from coarse to fine by using 180# to 2000# metallographic sandpaper, and then polishing by using a special polishing cloth and a diamond polishing liquid.

[0017] Preferably, the workpiece voltage of the ion bombardment cleaning in step (1) is 300-500 V, and the bombardment time is 1 h; the Ar + The target material is bombarded by plasma for not less than 30 min, and the target material voltage is not less than 800 V.

[0018] Preferably, the gradient coating preparation method in step (2) is a double glow plasma surface metallurgy technology, and the process parameters are an inter-electrode distance of 10-20 mm, a chamber gas pressure of 15-35 Pa, a workpiece current of 2.5-3.5 A, a target material current of 0.5-1.5 A, and a heat preservation time of 3-8 h.

[0019] Preferably, the first stage temperature rising speed in step (3) is 5 ℃ / min, the heat preservation temperature is 300-500 ℃, and the heat preservation time is 1-3 h; the second stage temperature rising speed is 3 ℃ / min, the heat preservation temperature is 600-800 ℃, and the heat preservation time is 5-10 h.

[0020] The above-mentioned one kind of medium-entropy (Zr, Ta, W) C coating is applied to prepare a wear-resistant protective coating.

[0021] Beneficial effects:

[0022] Compared with the prior art, the wear-resistant and toughened medium-entropy (Zr, Ta, W) C gradient coating is prepared by a double-layer glow plasma surface metallurgy method and a gradient temperature annealing technology, hardness is not less than 25 GPa, fracture toughness is not less than 3.5 MPa*m 1 / 2 , and coating adhesion is not less than 50 N. Compared with traditional preparation methods (such as plasma spraying, vapor deposition, magnetron sputtering, etc.), the coating prepared by the double-layer glow plasma surface metallurgy technology has the advantages of being dense and uniform, having a continuous gradient structure, and being able to produce a gradient metallurgical bond between the coating and the substrate, which makes the medium-entropy (Zr, Ta, W) C coating have very good bonding strength with the substrate material. And the gradient temperature annealing is a "stable first and strong later" gradient design, which avoids the limitations of single temperature treatment. In the low-temperature annealing stage, the accumulated internal stress in the coating can be released to improve the density and inhibit the coarsening and segregation of brittle phases; in the high-temperature annealing stage, the supersaturated solid solution in the coating gradually changes into a stable phase, the element diffusion is more sufficient, the solid solution composition uniformity is improved, and the surface lubrication performance is improved.

[0023] has the following advantages:

[0024] (1) The (Zr, Ta, W) C coating promotes uniform distribution of elements by means of multi-component elements, avoids the performance short board of single carbide, enhances the dislocation movement resistance to improve the hardness, strengthens the plastic deformation resistance and abrasive wear resistance of the coating, and guarantees high wear resistance; at the same time, the formation of a uniform single-phase solid solution structure endows the coating with good chemical stability, a thin and stable composite oxide film can be formed in the friction process to play a solid lubrication role to reduce the friction coefficient, and the synergistic optimization of high hardness, good toughness and stable lubrication performance is realized.

[0025] (2) The double-layer glow plasma surface metallurgy technology has the functions of multi-element composite plating, the prepared coating has the advantages of being dense and uniform, having a continuous gradient structure, and being able to produce a gradient metallurgical bond between the coating and the substrate, so that the coating and the substrate have good bonding strength, and the reliability and service life in the service process can be well improved.

[0026] (3) The gradient temperature annealing is a "stable first and strong later" gradient design, which avoids the limitations of single temperature treatment. In the low-temperature annealing stage, the accumulated internal stress (such as lattice distortion and dislocation) in the coating is released to reduce the risk of cracking, and short-range atomic diffusion is used to heal micro-pores, grain boundary voids and other micro defects to improve the density and inhibit the coarsening and segregation of brittle phases; in the high-temperature annealing stage, the elements are uniformly distributed, the solid solution structure is stable, the grains are moderately and uniformly grown to balance the hardness and toughness, the interface bonding between the strengthened coating and the substrate is improved, and the chemical stability is improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1Friction coefficient curve of (Zr, Ta, W)C gradient coating prepared for example 2 under ball-on-disc friction test under 4N, 6N, 8N load;

[0028] Figure 2 XRD pattern of surface of (Zr, Ta, W)C gradient coating prepared for example 2;

[0029] Figure 3 Surface morphology of (Zr, Ta, W)C gradient coating prepared for example 2;

[0030] Figure 4 Hardness comparison chart of coating prepared by 5 preparation processes of the application;

[0031] Figure 5 Structure schematic diagram of medium-entropy (Zr, Ta, W)C coating prepared by the application, 1-base, 2-diffusion layer, 3-deposition layer. DETAILED DESCRIPTION

[0032] A medium-entropy (Zr, Ta, W)C coating, the medium-entropy coating comprises the following components by mass fraction: ZrC 35% to 45%, TaC 35% to 45%, WC 10% to 30%, and the total amount is 100%; the medium-entropy (Zr, Ta, W)C coating is a gradient composite coating, comprising a base, a diffusion layer and a deposition layer from bottom to top, and the structure is as shown in Figure 5 The main components of the deposition layer material are ZrC, TaC and WC, atoms in the base material diffuse to the deposition layer, Zr atoms, Ta atoms, W atoms and C atoms in the deposition layer diffuse to the base material, a metallurgical bond is formed between the deposition layer and the base material, and a diffusion layer is formed at the interface between the deposition layer and the base; the hardness is 25 to 30 GPa, and the fracture toughness is 4.0 to 5.0 MPa*m 1 / 2 , the wear rate is less than 4*10 -6 mm 3 N -1 m -1 .

[0033] Preferably, the material of the base is a titanium alloy material or an iron-based alloy material.

[0034] The preparation method of the above-mentioned medium-entropy (Zr, Ta, W)C coating comprises the following steps:

[0035] (1) Base surface treatment

[0036] The chamber of the double glow plasma surface metallurgy equipment furnace body is cleaned by sandpaper and alcohol, the physically polished base material is fixed on the sample piece table, the distance between the upper surface of the base and the target material (the distance between the poles) is adjusted, the chamber is closed, the vacuum degree is extracted to 0.1 Pa, then the protective gas argon is introduced, and the chamber gas pressure is kept below 40 Pa; the Ar + plasma is used to ion bombard and clean the upper surface of the base;

[0037] (2) Gradient coating preparation

[0038] After the cleaning, the workpiece current, the target material current and the chamber pressure of the double glow plasma surface metallurgy equipment are adjusted to prepare the coating on the upper surface of the base; after the heat preservation is completed, the double glow furnace cooling work is started, the cooling time is not less than 1.5 h, the cooling is realized by reducing the target material current and the workpiece current, and when the room temperature is reached, the sample is taken out of the double glow furnace and is ultrasonically cleaned in anhydrous ethanol for standby;

[0039] (3) Gradient temperature annealing

[0040] The sample is placed in a crucible, then the crucible with the sample is slowly placed in the center of the furnace tube constant temperature zone, the furnace tube is sealed, the vacuum degree is extracted to 0.1 Pa, then the Ar gas is introduced as the protective gas; the furnace program is set, the first stage is to make the temperature rise from room temperature to the annealing low temperature stage and keep the temperature; the second stage is to continue to rise to the annealing high temperature stage and keep the temperature; after the heat preservation is completed, the heating power is turned off, the sample is cooled with the furnace, the vacuum state is kept until the room temperature is reached, then the slow air release is carried out to the normal pressure, and the sample is taken out.

[0041] Preferably, the physical polishing and polishing in step (1) refer to the polishing of the upper surface of the base material sample from coarse to fine by using the metallographic sandpaper with the grit of 180# to 2000#, and then the polishing by using the special polishing cloth and the diamond polishing liquid.

[0042] Preferably, the workpiece voltage of the ion bombardment cleaning in step (1) is 300-500 V, and the bombardment time is 1 h; the Ar + plasma bombardment cleaning of the target material is not less than 30 min, and the target material voltage is not less than 800 V.

[0043] Preferably, the gradient coating preparation method in step (2) is the double glow plasma surface metallurgy technology, the process parameters are as follows: the distance between the poles is 10-20 mm, the chamber gas pressure is 15-35 Pa, the workpiece current is 2.5-3.5 A, the target material current is 0.5-1.5 A, and the heat preservation time is 3-8 h.

[0044] Preferably, the first stage of step (3) has a temperature rising speed of 5℃ / min, a temperature holding temperature of 300-500℃, and a temperature holding time of 1-3h; the second stage has a temperature rising speed of 3℃ / min, a temperature holding temperature of 600-800℃, and a temperature holding time of 5-10h.

[0045] Use of the (Zr,Ta,W)C coating in the preparation of wear-resistant protective coatings.

[0046] The application will be further described by the following examples, but is not limited to the following examples.

[0047] Example 1

[0048] In this example, titanium alloy is used as the base material. To ensure the bonding strength between the titanium alloy and the coating, the upper surface of the titanium alloy sample is polished from coarse to fine using 180# to 2000# metallographic sandpaper, and then polished using a special polishing cloth and diamond polishing liquid, and ultrasonically cleaned in anhydrous ethanol for standby use.

[0049] The chamber of the double glow plasma surface metallurgy equipment furnace body is opened, the chamber is wiped with sandpaper and cleaned with alcohol, the titanium alloy material base is placed on the sample table as the cathode, the ZrC, TaC and WC single-component grid target is placed on the target material rack as the source electrode, the distance between the cathode and the source electrode is adjusted to 10mm, the chamber is closed, protective argon gas is introduced, and the chamber pressure is controlled at 35Pa. The base sample is ion bombarded in the double-layer glow plasma surface metallurgy equipment, the workpiece (cathode) voltage is set to 300V, and the bombardment time is 1h. Then the workpiece (cathode) current is 2.5A, the target material (source electrode) current is 1.5A, and the holding time is 6h. After the sputtering time reaches, the source electrode and the workpiece current are reduced to 0A and 1.0A respectively, and the equipment is turned off. When the temperature drops to room temperature, the sample is taken out of the double glow furnace and ultrasonically cleaned in anhydrous ethanol. Then the sample is placed in a crucible, the crucible with the sample is slowly placed in the center of the furnace tube constant temperature zone, the furnace tube is sealed, the vacuum degree is extracted to 0.1Pa, and then Ar gas is introduced as the protective gas; the furnace program is set, the first stage is set to increase the temperature from room temperature to 500℃ at a speed of 5℃ / min, and the holding time is set to 3h; the second stage is set to increase the temperature from 500℃ to 800℃ at a speed of 3℃ / min, and the holding time is set to 10h, and the sample is annealed; after the holding time ends, the heating power is turned off, and the sample is cooled with the furnace, and the Ar gas protection state is maintained until the temperature drops to room temperature. Then the gas is slowly released to normal pressure, and the sample is taken out.

[0050] The prepared sample is observed by scanning electron microscope, the bonding strength is tested by scratch method, and the surface hardness is tested by nanoindentation method; the ball-on-disc friction experiment is carried out under a load of 4N, 6N and 8N.

[0051] The results show that there is no obvious crack on the surface and cross section of the coating under scanning electron microscope. The thickness of the coating is 29 μm, the hardness is 25.4 GPa, the adhesion of the deposited layer is 56.6 N, and the fracture toughness is 4.1 MPa*m 1 / 2 The wear rate is 3.51*10 -6 mm 3 N -1 m -1 after the ball-disk friction experiment under 25℃ room temperature and 8N load for 15 minutes. The coating has good mechanical properties. The coating is not worn out in the ball-disk friction experiment, and the friction coefficient curve has no sharp fluctuation. The friction coefficient under 8N load does not exceed 0.4. The coating has good wear resistance and lubrication performance.

[0052] Example 2

[0053] In this embodiment, titanium alloy is used as the base material. In order to ensure the bonding strength between the titanium alloy and the coating, the upper surface of the titanium alloy sample is polished from coarse to fine by using 180# to 2000# metallographic sandpaper, and then polished by using special polishing cloth and diamond polishing liquid, and ultrasonically cleaned in anhydrous ethanol for standby.

[0054] The chamber of the double glow plasma surface metallurgy equipment furnace body is opened, the chamber is wiped with sandpaper and cleaned with alcohol, the titanium alloy material base is placed on the sample table as the cathode, the ZrC, TaC and WC single-component grid target is placed on the target material rack as the source electrode, the distance between the cathode and the source electrode is adjusted to 15mm, the chamber is closed, the protective gas argon is introduced, the chamber pressure is controlled at 25Pa, the base sample is ion bombarded in the double-layer glow plasma surface metallurgy equipment, the workpiece (cathode) voltage is set to 300V, and the bombardment time is 1h. Then the workpiece (cathode) current is 3A, the target material (source electrode) current is 1A, and the holding time is 6h. After the sputtering time reaches, the source electrode and the workpiece current are respectively reduced to 0A and 1.0A, and then the equipment is closed. When the temperature decreases to room temperature, the sample is taken out from the double glow furnace and ultrasonically cleaned in anhydrous ethanol. Then the sample is placed in a crucible, the crucible with the sample is slowly placed in the center of the furnace tube constant temperature zone, the furnace tube is sealed, the vacuum degree is extracted to 0.1Pa; then Ar gas is introduced as the protective gas; the furnace program is set, the first stage: the temperature is set to rise from room temperature to 400℃, the heating rate is set to 5℃ / min, and the holding time is set to 2h; the second stage: the temperature is set to rise from 400℃ to 700℃, the heating rate is set to 3℃ / min, and the holding time is set to 8h, the sample is annealed; after the holding time ends, the heating power is turned off, and the sample is cooled with the furnace, and the Ar gas protection state is maintained until the temperature cools to room temperature. Then the gas is slowly released to normal pressure, and the sample is taken out.

[0055] The prepared sample is observed by scanning electron microscope for surface and cross section, tested by scratch method for bonding strength, and tested by nano indentation method for surface hardness; ball-disk friction experiment is carried out under 4N, 6N and 8N load, and the results are shown in Figure 1 .

[0056] The results show that under the scanning electron microscope, the surface and cross section of the coating have no obvious cracks, and the surface morphology of the coating is shown in Figure 3 . The coating thickness is 25μm, the hardness is 29.2GPa, the bonding strength of the deposited layer is 72.7N, and the fracture toughness is 4.8MPa*m 1 / 2 . The wear rate after 15-minute ball-disk friction experiment under 8N load at 25℃ room temperature is 1.72×10 -6 mm 3 N -1 m -1 . The coating has good mechanical properties. In the ball-disk friction experiment, the coating is not worn through, the friction coefficient curve is smooth, the highest friction coefficient under 8N load is about 0.3, the coating has excellent wear resistance and lubrication performance.

[0057] Example 3

[0058] In this example, titanium alloy is used as the base material. In order to ensure the bonding strength of titanium alloy and the coating, the upper surface of the titanium alloy sample is polished from coarse to fine by using 180# to 2000# metallographic sandpaper, then polished by using special polishing cloth and diamond polishing liquid, and cleaned by ultrasonic cleaning in anhydrous ethanol for standby.

[0059] The chamber of the double glow plasma surface metallurgy equipment furnace body is opened, the chamber is wiped and cleaned with sandpaper and alcohol, a titanium alloy material base is placed on the sample table as a cathode, ZrC, TaC and WC single-component grid targets are placed on the target material rack as anodes, the distance between the cathode and the anode is adjusted to 20 mm, the chamber is closed, protective argon gas is introduced, the chamber pressure is controlled at 15 Pa, ion bombardment is performed on the base sample in the double-layer glow plasma surface metallurgy equipment, the workpiece (cathode) voltage is set to 300 V, and the bombardment is performed for 1 h. Then the workpiece (cathode) current is 3.5 A, the target material (anode) current is 0.5 A, and the holding time is 6 h. After the sputtering time reaches, the source and workpiece currents are reduced to 0 A and 1.0 A respectively, and the equipment is closed. When the temperature is reduced to room temperature, the sample is taken out of the double glow furnace and placed in anhydrous ethanol for ultrasonic cleaning. Then the sample is placed in a crucible, the crucible with the sample is slowly placed in the center of the furnace tube constant temperature zone, the furnace tube is sealed, the vacuum degree is extracted to 0.1 Pa; then Ar gas is introduced as a protective gas; the furnace program is set, the first stage: the temperature is set to rise from room temperature to 300 DEG C, the heating rate is set to 5 DEG C / min, and the holding time is set to 1 h; the second stage: the temperature is set to rise from 300 DEG C to 600 DEG C, the heating rate is set to 3 DEG C / min, and the holding time is set to 5 h, and the sample is annealed; after the holding time ends, the heating power is turned off, and the sample is cooled with the furnace, and the Ar gas protection state is maintained until the temperature is cooled to room temperature. Then slowly release to normal pressure, take out the sample.

[0060] The prepared sample is observed by a scanning electron microscope, the adhesion is tested by a scratch method, and the surface hardness is tested by a nanoindentation method; ball-on-disc friction experiments are performed under loads of 4N, 6N and 8N.

[0061] The results show that under the scanning electron microscope, the coating surface and the cross section are free of obvious cracks. The thickness of the coating is 20 μm, the hardness is 25.9 GPa, the deposition layer adhesion is 60.2 N, and the fracture toughness is 4.3 MPa*m 1 / 2 After the 15-minute ball-on-disc friction experiment at 25 DEG C room temperature and under a load of 8N, the wear rate is 3.24*10 -6 mm 3 N -1 m -1 . The coating has good mechanical properties. In the ball-on-disc friction experiment, the coating is not worn through, and the friction coefficient curve does not appear to fluctuate sharply, the highest friction coefficient under a load of 8N is about 0.35, and the coating also has good wear resistance and lubrication performance.

[0062] Comparative Example 1

[0063] TiC ceramic coating was prepared by using the commonly used atmospheric plasma spraying method. The equipment used was a 100HE plasma spraying system, the coating was deposited on the surface of titanium alloy material, the spraying distance was 90 mm, the powder feeding rate was 40 g / min, and the spraying power was 30 kW.

[0064] The prepared sample was observed by scanning electron microscope for surface and cross section, the bonding strength was tested by scratch method, and the surface hardness was tested by nano indentation method; ball-on-disc friction experiment was carried out under the load of 4N, 6N and 8N.

[0065] The results show that under the scanning electron microscope, the thickness of the coating is 69 μm, the porosity and roughness of the coating are higher than those of the coating prepared by the double glow plasma surface metallurgy method. The hardness is 19.8 GPa, the bonding strength of the deposited layer is less than 10 N, and the fracture toughness is 1.7 MPa*m 1 / 2 After 15 minutes of ball-on-disc friction experiment at room temperature of 25℃ and under the load of 8N, the wear rate is 3.02×10 -5 mm 3 N -1 m -1 . The mechanical properties are poor. And the friction coefficient fluctuates greatly in the ball-on-disc friction experiment, the highest friction coefficient has exceeded 0.6, the wear resistance and lubrication performance are poor. It is shown that the TiC coating prepared by atmospheric plasma spraying method does not have good wear resistance and lubrication performance.

[0066] Comparative example 2

[0067] In this embodiment, titanium alloy is used as the substrate material. In order to ensure the bonding strength of titanium alloy and coating, the upper surface of titanium alloy sample is polished from coarse to fine by using 180# to 2000# metallographic sandpaper, then polished by using special polishing cloth and diamond polishing liquid, and ultrasonically cleaned in anhydrous ethanol for standby.

[0068] The chamber of the double glow plasma surface metallurgy equipment furnace body is opened, the chamber is wiped with sandpaper and cleaned with alcohol, the titanium alloy material substrate is placed on the sample table as the cathode, the ZrC, TaC and WC single component grid target is placed on the target material rack as the source electrode, the distance between the cathode and the source electrode is adjusted to 15 mm, the chamber is closed, the protective gas argon is introduced, and the chamber pressure is controlled at 25 Pa. The upper surface of the substrate material is not bombarded and cleaned. Then the workpiece (cathode) current is 3A, the target material (source electrode) current is 1A, and the holding time is 6h. After the sputtering time reaches, the source electrode and the workpiece current are respectively reduced to 0A and 1.0A, and then the equipment is closed. When the room temperature is reduced, the sample is taken out from the double glow furnace and ultrasonically cleaned in anhydrous ethanol. Then no annealing treatment is carried out, and the subsequent test is carried out directly.

[0069] The prepared sample is observed by scanning electron microscope for surface and cross section, tested by scratch method for bonding force, and tested by nanoindentation method for surface hardness; ball-disk friction experiment is carried out under 4N, 6N and 8N load.

[0070] The results show that under scanning electron microscope, the thickness of the coating is about 15 μm, and obvious cracks appear on the surface and cross section of the coating; the hardness is 24.6 GPa, the bonding force of the deposited layer is 50.5 N, and the fracture toughness is 2.4 MPa*m 1 / 2 After 15-minute ball-disk friction experiment under 8N load at 25℃ room temperature, the wear rate of the coating is 1.94*10 -5 mm 3 N -1 m -1 The mechanical properties of the coating are poorer than those of the coating in the embodiment. In the ball-disk friction experiment, the coating is worn out, and the friction coefficient curve fluctuates sharply, indicating that the coating prepared without plasma bombardment cleaning and annealing treatment on the surface of the substrate does not have good wear resistance and lubrication performance.

[0071] Table 1: Performance data of materials prepared in different embodiments and comparative examples

[0072]

[0073] In summary, the high-wear-resistance and lubrication-performance middle-entropy (Zr, Ta, W) C coating of the application can realize excellent wear resistance and lubrication performance while having good mechanical properties, and is particularly suitable for the field of wear-resistant protective coating.

[0074] The above description of the application and its embodiments is illustrative, and is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual structure is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired by the above description, without departing from the spirit of the application, similar structural modes and embodiments can be designed without creative design, and all should belong to the protection scope of the application.

Claims

1. A medium entropy (Zr, Ta, W) C coating, characterized by: The medium-entropy coating includes the following components by mass fraction: ZrC 35% to 45%, TaC 35% to 45%, and WC 10% to 30%, with a total of 100%; the medium-entropy (Zr, Ta, W) C coating is a gradient composite coating, which includes, from bottom to top, a substrate, a diffusion layer, and a deposition layer; the main components of the deposition layer material are ZrC, TaC, and WC, atoms in the substrate material diffuse into the deposition layer, and Zr atoms, Ta atoms, W atoms, and C atoms in the deposition layer diffuse into the substrate material, forming a metallurgical bond between the deposition layer and the substrate, and forming a diffusion layer at the interface between the deposition layer and the substrate; the hardness is 25 to 30 GPa, and the fracture toughness is 4.0 to 5.0 MPa*m 1 / 2 , 15 minutes at room temperature, 8N load wear rate is less than 4×10 -6 mm 3 N -1 m -1 .

2. The medium-entropy (Zr, Ta, W)C coating according to claim 1, characterized in that: The material of the substrate is titanium alloy material or iron-based alloy material.

3. A method for preparing a medium-entropy (Zr, Ta, W)C coating according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Substrate surface treatment Use sandpaper to wipe and alcohol to clean the chamber of the double glow plasma surface metallurgy equipment furnace body, fix the physically polished base material on the sample table, adjust the distance between the upper surface of the base and the target material (electrode distance), close the chamber, pump the vacuum degree to 0.1Pa, and then introduce protective gas argon, and keep the chamber pressure below 40Pa; use the Ar in the double glow plasma surface metallurgy equipment to + The plasma performs ion bombardment cleaning on the upper surface of the substrate; (2) Gradient coating preparation After cleaning, the workpiece current, target current and chamber pressure of the double-glow plasma surface metallurgy equipment are adjusted to prepare a coating on the substrate surface; After the insulation is completed, the double glow furnace is cooled down for no less than 1.5 hours. The cooling is achieved by reducing the target current and the workpiece current. When the temperature drops to room temperature, the sample is taken out of the double glow furnace and ultrasonically cleaned in anhydrous ethanol for later use. (3) Gradient temperature annealing Place the sample in a crucible, then slowly place the crucible with the sample in the center of the constant temperature zone of the furnace tube, seal the furnace tube, pump the vacuum degree to 0.1 Pa, and then introduce Ar gas as a protective gas; set the furnace program, the first stage: raise the temperature from room temperature to the annealing low temperature stage, and keep it warm; the second stage: continue to raise the temperature to the annealing high temperature stage, and keep it warm; after the insulation is completed, turn off the heating power supply, let the sample cool with the furnace, maintain the vacuum state and cool to room temperature, then slowly vent to normal pressure and take out the sample.

4. The preparation method according to claim 3, wherein: The physical grinding and polishing described in step (1) refers to using 180# to 2000# metallographic sandpaper to grind the upper surface of the base material sample from coarse to fine, and then polishing it using a special polishing cloth and diamond polishing liquid.

5. The preparation method according to claim 3, wherein: The workpiece voltage of the ion bombardment cleaning in step (1) is 300-500V, and the bombardment time is 1h; Ar + The target material shall be cleaned by plasma bombardment for no less than 30 minutes, and the target material voltage shall be no less than 800V.

6. The preparation method according to claim 3, wherein: The gradient coating preparation method described in step (2) is double glow plasma surface metallurgy technology, and the process parameters are: inter-electrode spacing of 10-20 mm, chamber pressure of 15-35 Pa, workpiece current of 2.5-3.5 A, target current of 0.5-1.5 A, and holding time of 3-8 h.

7. The preparation method according to claim 3, wherein: In the first stage of step (3), the heating rate is 5°C / min, the holding temperature is 300-500°C, and the holding time is 1-3h; in the second stage, the heating rate is 3°C / min, the holding temperature is 600-800°C, and the holding time is 5-10h.

8. Use of a medium entropy (Zr, Ta, W)C coating according to claim 1 in preparing a wear-resistant protective coating.

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