Wear-resistant protective composite coating and use thereof

Abstract

The application relates to a wear-resistant protective composite coating and application thereof, and utilizes a supersonic flame spraying technology to spray a Cr3C2-NiCr coating, the coating is formed by combining the advantages of Cr3C2-NiCr material and supersonic spraying, and is a novel material with the advantages of high-temperature resistance, oxidation resistance, corrosion resistance, high-temperature wear resistance, high-temperature erosion resistance, low porosity and the like; then, a TaC coating is prepared by using an arc ion plating, the coating has a bottom layer of NiCr and a transition layer of Ti, has the characteristics of low deposition temperature, simple operation and strong applicability, can improve the bonding performance between the Cr3C2-NiCr layer and the TaC coating which are materials with different compositions, the average friction coefficient of the Cr3C2-NiCr coating in an atmospheric environment is above 0.4, the wear rate is 10-14 m 3 / N•m order of magnitude; after the TaC coating is prepared, the friction coefficient is as low as below 0.1, the hardness is above HV3000, and the wear rate is 10-18 m 3 / N•m order of magnitude.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating, and particularly relates to a wear-resistant protective composite coating and application thereof. BACKGROUND

[0002] Due to the energy structure and reserves proportion of China, coal occupies an absolute advantage, and the implementation of modern coal chemical industry is beneficial to the energy security of the country. In the era of high oil prices, with the completion and production of large-scale coal chemical industry, the competitiveness of coal chemical products is also increasing. The high-efficiency and reasonable utilization of coal is realized by using coal conversion high-tech, and the economy is optimized and the environment is friendly. Coal chemical industry is an industry that produces chemical products through various processes with coal as the main raw material. Unlike traditional coal chemical industry, "coal-to-oil" is modern coal chemical industry, such as coal gasification to alcohol, ether fuel and coal liquefied fuel. "Coal-to-oil" process technology: South Africa first realized large-scale commercial application of coal indirect liquefaction technology of new coal chemical industry. Sasol company in South Africa uses two important devices of Lurgi gasifier and F / T synthesis reactor to synthesize liquefied fuel with an annual output of about 10 million tons. Coal-to-oil and petrochemical-to-oil are significantly different in principle and process: 1. raw material: the raw material of petrochemical-to-oil is crude oil, while the raw material of coal-to-oil is raw coal; 2. process: petrochemical-to-oil is a cracking process of liquid crude oil, while coal-to-oil is a gasification process or liquefaction process of raw coal. At the same time, the application of related new technologies and new equipment in modern coal chemical industry is beneficial to the improvement of coal conversion rate and the reduction of production cost, which is conducive to the industrialization and commercialization of coal-to-oil industry as a whole.

[0003] The process route and method of modern "coal-to-oil" is to use raw coal without special requirements, and to convert solid coal into liquid petroleum products through certain process processing method. The process is mainly divided into direct liquefaction and indirect liquefaction. Direct liquefaction is to prepare coal slurry with solvent by grinding coal powder, and then to convert it into oil under the extreme synthesis conditions of high temperature and high pressure hydrogenation treatment. Indirect liquefaction is to gasify coal powder at high temperature, and then to synthesize oil by further catalytic hydrogenation treatment. The conditions of the two processes are high temperature (350-480℃), high pressure (20-30MPa), flammable, explosive, corrosion and wear, etc. The first direct liquefaction process technology of coal-to-oil technology of Shenhua Group in China is the main production equipment of "coal-to-oil" industry, including system devices composed of tower, tank and pipeline, among which valve is an important control equipment. Commonly used gate, stop, ball and butterfly valves are conventional parts in the system.

[0004] But the harsh conditions of direct liquefaction technology makes the valve need to withstand high temperature (up to 480 ℃), high pressure (up to 30 MPa), hydrogen, oxygen, flammable, explosive, corrosion, wear and other process characteristics, so its structure is mainly high temperature and high pressure metal seal wear resistant ball valve. The design and structure design of the sealing material of high temperature and high pressure wear resistant ball valve is the technical difficulty of this kind of valve, but also the key point to ensure the reliability of the equipment.

[0005] At present, high temperature and high pressure metal seal wear resistant ball valve relies on import, expensive. With the need of localization of high parameter, high performance valve, the development of high parameter wear resistant ball valve becomes very urgent, the selection of sealing material and process implementation becomes urgent requirement. When the medium temperature of pipeline is high, the pressure is large and contains particle impurities, metal valve seat sealing valve must be selected, and the ball sealing surface and valve seat sealing surface need to be hardened to ensure that the valve meets the valve leakage requirements in the specification, so as to prolong the service life of the valve seat.

[0006] In short, the failure mode of ball valve is mainly caused by surface wear and corrosion in working environment. The above working conditions require high wear resistance. In engineering application, stainless steel parts are prone to surface fatigue under load, such as gear pitting, surface cracks include three stages: crack initiation, crack propagation and cracking. Long-term stable service of parts used in harsh working conditions requires the preparation of high wear-resistant and corrosion-resistant coating on the surface, which is of great significance in reducing maintenance, saving materials and reducing energy consumption.

[0007] In the black water flash process of coal to olefin industry, the solid particles in the medium after gasification will erode the valve at high speed. Therefore, ceramic ball valve is mostly used in black water regulation working condition. The commonly used materials are Ni60, WC and Zr2O3 toughened alumina ceramic, with hardness above 89HRA, strong wear resistance and erosion resistance. The coating prepared by the above method has single performance and cannot realize good wear resistance and corrosion resistance of parts in acidic environment; diamond-like thin film includes hydrogen containing DLC film with high hardness and elastic modulus, and the composition of DLC film contains high content of hydrogen, which can provide strong internal stress for DLC film. The internal stress can make the interface of DLC film have lubricating effect, so that DLC film has high wear resistance, low friction coefficient and surface wear resistance, but too much hydrogen element will reduce the elastic modulus of DLC film and the bonding force of the body; diamond-like thin film also includes TaC coating with higher elastic modulus and hardness, which is a hydrogen free carbon coating with high sp³ / sp² ratio. Compared with other DLC coatings, TaC film has higher hardness and temperature resistance, and the friction coefficient of TaC film is higher.

[0008] However, there is still a lack of research on the combination of Cr3C2-NiCr coating and TaC coating. SUMMARY

[0009] The present application aims to overcome the shortcomings and deficiencies of the prior art and provide a wear-resistant protective composite coating and its application.

[0010] The first aspect of the present application is to provide a wear-resistant protective composite coating, which comprises a Cr3C2-NiCr coating and a TaC coating, and the TaC coating is located outside the Cr3C2-NiCr coating.

[0011] Preferably, the TaC coating comprises a NiCr primer layer, a Ti transition layer and a carbon plating layer, the NiCr primer layer is located between the Cr3C2-NiCr coating and the Ti transition layer, and the Ti transition layer is located between the carbon plating layer and the NiCr transition layer.

[0012] Preferably, the thickness of the Cr3C2-NiCr coating is 70-150 μm, and the thickness of the TaC coating is 5-8 μm.

[0013] Preferably, the TaC coating is prepared by arc ion plating method.

[0014] Preferably, the preparation of the TaC coating comprises the following steps:

[0015] (1) Pre-treating the surface of the substrate coated with the Cr3C2-NiCr layer;

[0016] (2) Loading the pre-treated substrate into a vacuum chamber, vacuumizing and heating, etching and cleaning the substrate under a bias voltage to remove dust and other impurities attached to the surface;

[0017] (3) After etching, introducing a protective gas, first opening the NiCr alloy target to deposit a NiCr primer layer, then opening the Ti target to deposit a Ti transition layer, and finally opening the graphite target to deposit a carbon layer, so as to obtain a TaC coating on the surface of the substrate after the coating deposition is completed.

[0018] Preferably, the Cr3C2-NiCr coating is prepared by supersonic flame spraying technology.

[0019] Preferably, the Cr3C2-NiCr coating comprises a hard phase and a binder phase, the content of the hard phase is 70-80 wt%, and the content of the binder phase is 20-30 wt%.

[0020] The second aspect of the present application is to provide the wear-resistant protective composite coating as described above for use on the surface of a valve.

[0021] Preferably, the valve is a ball valve, and comprises a valve seat and a ball, the wear-resistant protective composite coating is formed on the surface of the valve seat, and the surface of the ball is provided with a wear-resistant infiltration layer, the hardness of the wear-resistant infiltration layer is 1000-1300 HV, and the hardness of the wear-resistant protective composite coating is 3000-3500 HV.

[0022] Preferably, the wear-resistant infiltration layer is a non-metallic element and a trace metallic element infiltrated on the surface of the ball through PIP composite treatment, so as to form a composite infiltration layer with oxides of metallic elements and carbonitrides of metallic elements.

[0023] The beneficial effects of the present application are as follows:

[0024] 1) The present application uses high-velocity oxygen fuel spraying technology to spray Cr3C2-NiCr coating, which combines the advantages of Cr3C2-NiCr material and high-velocity spraying, forming a new material with the advantages of high-temperature resistance, oxidation resistance, corrosion resistance, high-temperature wear resistance, high-temperature erosion resistance, low porosity, etc. Then, TaC coating is prepared by arc ion plating, with NiCr as the primer layer and Ti as the transition layer, which has the characteristics of low deposition temperature, simple operation and strong applicability, and can improve the bonding performance between the two materials with different compositions, Cr3C2-NiCr coating, the average friction coefficient in the atmospheric environment is above 0.4, the wear rate is 10-14 m 3 / N•m order of magnitude; while the friction coefficient of the prepared TaC coating is as low as 0.1 or below, the hardness is HV3000, and the wear rate is 10-18 m 3 / N•m order of magnitude;

[0025] 2) The present application combines high-velocity oxygen fuel spraying and arc ion plating to prepare Cr3C2-NiCr coating on the sealing surface of the valve seat and TaC coating on the surface of the valve seat, forming a TaC / Cr3C2-NiCr composite coating. This coating not only maintains the good wear resistance, corrosion resistance and high-temperature oxidation resistance of traditional Cr3C2-NiCr hard coating, but also has excellent self-lubricating properties of graphite material. The coating composition tends to be diversified and composite, which can solve the problem of severe wear of single Cr3C2-NiCr coating. The PIP surface treatment is used to prepare a multi-element infiltration layer on the surface of the ball, so that there is a certain hardness difference between the valve seat and the ball friction pair, improving the comprehensive performance and service life of the ball valve. The ball valve and other stainless steel parts serving in high-temperature friction, acid and alkali environments have good protective effect, thereby effectively improving the comprehensive performance and service life of the substrate, meeting the urgent needs of the rapid development of modern mechanical industry for surface protection of parts, and having good application value. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative labor.

[0027] Figure 1 is a cross-sectional thickness test result diagram of the sprayed Cr3C2-NiCr with 06Cr19Ni10 as the base body in the embodiment 1 of the present application;

[0028] Figure 2 is a cross-sectional thickness test result diagram of the TaC / Cr3C2-NiCr with 06Cr19Ni10 as the base body in the embodiment 1 of the present application;

[0029] Figure 3 is a cross-sectional thickness test result diagram of the TaC / Cr3C2-NiCr with 0Cr17Ni12Mo2 as the base body in the embodiment 2 of the present application;

[0030] Figure 4 is a surface hardness test result diagram of the PIP surface composite treatment of the 06Cr19Ni10 sample and the 0Cr17Ni12Mo2 sample in the embodiment 1 and the embodiment 2 of the present application;

[0031] Figure 5 is a ball valve switching test result of the embodiment 1 and the embodiment 2 of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will further describe the present application in combination with the drawings.

[0033] The thickness of the wear-resistant protective composite coating is 75-158 μm, wherein the thickness of the Cr3C2-NiCr coating is 70-150 μm, the thickness of the TaC coating is 5-8 μm, and the thickness of the composite layer after the PIP surface composite treatment is 100-200 μm,

[0034] The Cr3C2-NiCr coating comprises a hard phase and a bonding phase, the hard phase comprises Cr3C2 particles, and the bonding phase adopts a NiCr alloy phase;

[0035] The content of the hard phase in the Cr3C2-NiCr coating is 70-80 wt%, and the content of the bonding phase is 20-30 wt%;

[0036] The TaC coating includes a NiCr primer layer, a Ti transition layer and a carbon plating layer, the NiCr layer is formed on the surface of the Cr3C2-NiCr coating, the Ti transition layer is formed on the NiCr primer layer, and the carbon plating layer is formed on the surface of the Ti transition layer.

[0037] The friction coefficient of the wear-resistant protective composite coating in an atmospheric environment is less than 0.1, the hardness is greater than 30 GPa (about 16 GPa for DLC), and the wear rate is 10 -18 m 3 / N·m (about 10 -16 m 3 / N·m) order of magnitude, the thickness of the PIP surface composite layer is 150-200 μm, the furnace temperature range is 450-500 ℃, the control time is 2-5 hours, and the concentration of the penetrant is 30%-40%, wherein the concentration of the penetrant is the percentage of C, N and O rare earth in the liquid.

[0038] 1. The process conditions of the supersonic flame spraying technology include: oxygen-fuel ratio 4.2-5.6, combustion chamber pressure 1.2-1.58 MPa, spraying distance 350-380 mm, spraying angle 60°-85°, oxygen flow rate 700-900 L / min, fuel flow rate 20-30 L / min, powder feeding gas pressure 0.8-1.2 MPa, and powder feeding flow rate 27-45 g / min; after the supersonic flame spraying is completed, the sealing surface is polished with diamond polishing paste, and then the sealing surface is finely polished with a barrel polisher.

[0039] 2. The TaC coating deposited by the arc ion plating technology consists of the following process steps:

[0040] (1) The valve seat surface is pretreated before deposition. After the surface oil stains are removed by wiping in petroleum ether and then ultrasonic cleaning in acetone for 30 minutes, the valve seat is ultrasonic cleaned in anhydrous ethanol for 15 minutes, and finally dried in a clean vacuum furnace;

[0041] (2) The PI series coating equipment is used to deposit the TaC coating, the part is loaded into the vacuum chamber, the chamber door is closed, vacuumizing and heating are performed, the vacuum is better than 7E-3Pa, the temperature reaches 130-160℃, the substrate is etched and cleaned under the bias voltage of-700 to-900V to remove the dust and other impurities attached to the surface, and the etching time is 80-100min. After the etching is completed, Ar gas is introduced and the molecular pump speed is adjusted to control the gas pressure in the vacuum chamber to be≤1E+0Pa. The NiCr target is opened first, and then the Ti target is opened, the target power is 5-7kw, the deposition time is 350-440min and 160-200min respectively, at this time the deposition gas pressure is controlled to be≤1.5E+0Pa by adjusting the Ar gas flow, the temperature in the chamber is adjusted to 30-50℃, the graphite target is opened, the bias voltage is-1200 to-1000V, the target current is 10-14A, the carbon layer is deposited, and the deposition time is 900-1200min. After the coating deposition is completed, the protective gas argon is filled into the chamber, the gas is discharged to the atmospheric pressure, the chamber is opened, and the TaC coating is obtained on the valve core surface. In the NiCr target, the content of Ni is 60-80at.%, and the content of Cr is 40-20at.%.

[0042] 3. The PIP composite treatment on the surface of the ball includes the following steps:

[0043] (1) The ball is cleaned to remove oil and rust, and the concentration of the penetrant is adjusted to 30%-40%, wherein the concentration of the penetrant is the percentage of rare earth C, N and O in the liquid;

[0044] (2) The ball is placed in a preheating furnace, the liquid in the furnace is preheated at a rate of 20-100℃ / h to 380-400℃, and the temperature is maintained for 1-2 hours;

[0045] (3) The ball is placed in a special basket and then immersed in the liquid in the salt bath furnace; the temperature is maintained at 450-500℃ for 2-5 hours;

[0046] (4) After the temperature maintenance is completed, the ball is placed in an oxidation furnace, the temperature is maintained at 480-500℃ for 1-2 hours, the heat source is cut off, the workpiece is cooled with the furnace, and the residual salt on the surface is cleaned when the temperature is below 100℃;

[0047] (5) After the surface of the ball is finely polished, a wear-resistant penetration layer is obtained.

[0048] Example 1

[0049] In this embodiment, the above-mentioned composite coating is prepared on the surface of a base material of 06Cr19Ni10 material, and the preparation method is specifically as follows:

[0050] 1. The Cr3C2-NiCr coating is sprayed by using the high-velocity oxygen fuel spraying technology, which consists of the following process steps:

[0051] (1) Pre-treatment before spraying

[0052] Sandblasting treatment was performed on the surface of the 06Cr19Ni10 valve seat. The abrasive used for sandblasting was corundum, the pressure of the compressed air for sandblasting was 0.2 MPa, the sandblasting distance was 100 mm, the sandblasting angle was 30°, and the surface roughness of the substrate after sandblasting was 2.5 μm. After sandblasting, the valve seat was cleaned with acetone.

[0053] (2) Preparation of Cr3C2-NiCr coating

[0054] JP8000 supersonic flame spraying equipment was used to spray the ball with Cr3C2-NiCr as the spraying powder, the oxygen-fuel ratio was 4.2, the combustion chamber pressure was 1.2 MPa, the spraying distance was 350 mm, the spraying angle was 60°, the oxygen flow rate was 700 L / min, the fuel flow rate was 20 L / min, the pressure of the powder feeding gas was 0.8 MPa, and the powder feeding flow rate was 27 g / min.

[0055] 2. PI series coating equipment was used to deposit the TaC coating, which consisted of the following process steps:

[0056] (1) The valve seat surface was pre-treated before deposition. After wiping off the surface oil stains in petroleum ether, the valve seat was ultrasonically cleaned in acetone for 30 minutes, then ultrasonically cleaned in anhydrous ethanol for 15 minutes, and finally dried in a clean vacuum furnace;

[0057] (2) PI series coating equipment was used to deposit the TaC coating. The part was loaded into the vacuum chamber, the chamber door was closed, vacuum was applied and heating was performed, so that the vacuum was better than 8E-3 Pa and the temperature reached 130°C. The substrate was etched and cleaned at a bias voltage of -700 V to remove dust and other impurities attached to the surface, and the etching time was 80 min. After etching, Ar gas was introduced and the molecular pump speed was adjusted to control the gas pressure in the vacuum chamber to be ≤6E+0 Pa. The NiCr target was first opened, and the deposition time was 350 min. Then the Ti target was opened, and the target power was 5 kW. The deposition time was 160 min. At this time, the deposition gas pressure was controlled to be ≤0.5E+0 Pa by adjusting the Ar gas flow rate. The temperature in the chamber was adjusted to 30°C. The graphite target was opened, the bias voltage was -1200 V, the target current was 10 A, and the carbon layer was deposited. The deposition time was 900 min. After the coating deposition was completed, the protective gas argon was filled into the chamber, the gas was released to atmospheric pressure, the chamber was opened, and the valve core was taken out. After the coating was completed, the valve core was cooled to room temperature in the furnace and then re-pressurized.

[0058] 3. The PIP composite treatment process of the 06Cr19Ni10 ball surface was divided into the following 5 steps:

[0059] (1) The ball is cleaned and degreased and rusted, and the concentration of the penetrant is 30%, wherein the concentration of the penetrant is the percentage of rare earth C, N and O in the liquid;

[0060] (2) The ball is placed in a preheating furnace, and the liquid in the furnace is preheated at a rate of 20℃ / h to 380℃, and kept for 1 hour;

[0061] (3) The ball is placed in a special basket and immersed in the liquid of the salt bath furnace; keep at 450℃ for 2h;

[0062] (4) After the heat preservation is finished, the ball is placed in an oxidation furnace, kept at 480℃ for 1 hour, the heat source is cut off, and the workpiece is cooled with the furnace until the temperature is below 100℃, and the residual salt on the surface is cleaned;

[0063] (5) After the ball surface is finely polished, a wear-resistant permeation layer is obtained.

[0064] The surface of the workpiece after the above composite treatment is detected as follows:

[0065] (1) The UMT-3 multifunctional friction and wear tester is used to evaluate the friction and wear life of 06Cr19Ni10 sample and the above composite coating sample in the atmospheric environment. The specific method is: φ6mm alumina ball and TaC / Cr3C2-NiCr composite coating sample are used as friction pair and reciprocally slide, the sliding frequency is 5.5 Hz, the load is 20 N, the environmental temperature is (27±3)℃, the relative humidity is (75±5)%, the experimental time is 240 min, and Φ=6mm ceramic ball is used as friction pair. The friction coefficient of TaC / Cr3C2-NiCr composite coating sample is 0.08, and the wear rate is calculated to be 10 -18 / mm 3 / Nm, and the sample after the above composite treatment greatly improves the wear resistance.

[0066] (2) The TaC / Cr3C2-NiCr composite coating sample is detected by scanning electron microscope, the cross-sectional thickness is as Figure 1 shown, the NiCr-Cr3C2 coating thickness is about 80μm, the NiCr primer layer thickness is about 1μm, the transition layer Ti thickness is about 175nm, the carbon layer thickness is about 3μm, and the total thickness of TaC is about 4.2μm.

[0067] (3) The MTS-Nano G200 nanoindentation test platform determines the hardness of the TaC / Cr3C2-NiCr composite coating sample by continuous stiffness method, and the test result shows that the hardness is 30.89Gpa, and the conversion relationship is: HV=100×HN≈3089, which shows good mechanical properties.

[0068] Example 2

[0069] In this embodiment, the composite coating is prepared on the surface of 0Cr17Ni12Mo2 substrate, and the preparation method is specifically as follows:

[0070] 1. The Cr3C2-NiCr coating is prepared by using the supersonic flame spraying technology, which consists of the following process steps:

[0071] (1) Pre-treatment before spraying

[0072] The method of this step is the same as that in Example 1;

[0073] (2) Preparation of Cr3C2-NiCr coating:

[0074] The method of this step is basically the same as that in Example 1, except that the process parameters are as follows: oxygen-fuel ratio 5.6, combustion chamber pressure 1.58 MPa, spraying distance 380 mm, spraying angle 85°, oxygen flow rate 900 L / min, fuel flow rate 30 L / min, powder feeding gas pressure 1.2 MPa, and powder feeding flow rate 45 g / min.

[0075] 2. The TaC coating is deposited by using the PI series coating equipment, which consists of the following process steps:

[0076] (1) The method of this step is the same as that in Example 1;

[0077] (2) The TaC coating is deposited by using the PI series coating equipment. The part is loaded into the vacuum chamber, the chamber door is closed, vacuum is pumped and heated, so that the vacuum is better than 1E-4 Pa, and the temperature reaches 160℃. The substrate is etched and cleaned at a bias voltage of -900 V to remove dust and other impurities attached to the surface. The etching time is 100 min. After etching, Ar gas is introduced and the molecular pump speed is adjusted to control the gas pressure in the vacuum chamber to be ≤5E+0 Pa. First, the NiCr target is opened, and deposited for 440 min. Then the Ti target is opened, and the target power is 5 kw. The deposition time is 200 min. At this time, the deposition gas pressure is controlled to be ≤9E+0 Pa by adjusting the Ar gas flow rate. The temperature in the chamber is adjusted to 50℃. The graphite target is opened, the bias voltage is -1000 V, the target current is 14 A, and the carbon layer is deposited. The deposition time is 1200 min. After the coating deposition is completed, the protective gas argon is filled into the chamber, and the gas is discharged to atmospheric pressure. The chamber is opened and the valve core surface obtains the TaC coating.

[0078] 3. The PIP composite treatment process of the 0Cr17Ni12Mo2 sphere consists of the following 5 steps:

[0079] (1) The method of this step is the same as that in Example 1;

[0080] (2) Place the sphere in a preheating furnace and preheat the liquid in the furnace to 400°C at a rate of 100°C / h, and keep it at that temperature for 2 hours;

[0081] (3) After placing the sphere in a special basket, immerse it in the salt bath liquid; keep it at 500℃ for 5 hours;

[0082] (4) After the heat preservation is completed, the ball is placed in the oxidation furnace and kept at 500°C for 2 hours. The heat source is cut off and the workpiece is cooled with the furnace until it reaches below 30°C. The residual salt on the surface is then removed from the furnace.

[0083] (5) The surface of the sphere is polished to obtain a wear-resistant infiltration layer.

[0084] The surface of the workpiece after the above composite treatment was subjected to the following performance tests:

[0085] 1) The surface hardness of 06Cr19Ni10 and 0Cr17Ni12Mo2 samples was tested using the HMV-G21 series Vickers microhardness tester. The test pressure was 50g and the holding time was 15s. Ten points were tested for surface hardness of each sample group. The maximum and minimum values ​​were removed and the average values ​​of the remaining values ​​were calculated. The values ​​were 1089 and 1152 respectively.

[0086] 2) A ball valve switching test device was used to test the friction pairs consisting of the valve seat and ball after processing in Examples 1 and 2. This device consisted of a pneumatic ball valve connected to a counter to detect the number of switching tests. A sealing test was performed after every 500 switching tests until the valve leaked or jammed (caused by coating damage). Switching tests were conducted on the untreated ball valves and the ball valves from Examples 1 and 2. The number of tests was recorded as follows: Figure 5 As shown, the number of switching cycles in Example 1 is as high as more than 50,000, which is about 7 times that of the untreated ball valve.

[0087] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A ball valve comprising a valve seat and a ball, characterized in that: The valve seat sealing surface is formed with a wear-resistant protective composite coating, and the ball surface is formed with a wear-resistant permeation layer, the hardness of the wear-resistant permeation layer is 1000-1300 HV, and the hardness of the wear-resistant protective composite coating is 3000-3500 HV, The wear-resistant protective composite coating comprises a Cr3C2-NiCr coating and a TaC coating, and the TaC coating is located outside the Cr3C2-NiCr coating. The TaC coating comprises a NiCr primer layer, a Ti transition layer and a carbon plating layer, the NiCr primer layer is located between the Cr3C2-NiCr coating and the Ti transition layer, and the Ti transition layer is located between the carbon plating layer and the NiCr transition layer. The thickness of the Cr3C2-NiCr coating is 70-150 μm, and the thickness of the TaC coating is 5-8 μm. The TaC coating is prepared by an arc ion plating method. The preparation method of the wear-resistant permeation layer comprises the following steps: (A) cleaning and rust removing the ball, and adjusting the concentration of the permeation agent to 30%-40%, wherein the concentration of the permeation agent is the percentage of C, N, O and rare earth in the liquid; (B) preheating the liquid in the furnace at a rate of 20-100 ℃ / h to 380-400 ℃, and keeping the temperature for 1-2 hours; (C) immersing the ball in the liquid in the salt bath furnace, and keeping the temperature at 450-500 ℃ for 2-5 hours; (D) after the temperature keeping, placing the ball in the oxidation furnace, keeping the temperature at 480-500 ℃ for 1-2 hours, cutting off the heat source, and cooling the workpiece with the furnace until the temperature is below 100 ℃, and then taking out the workpiece and cleaning the residual salt on the surface; (E) after fine polishing the surface of the ball, a wear-resistant permeation layer is obtained.

2. A ball valve according to claim 1, characterised in that: The preparation of the TaC coating comprises the following steps: (1) pre-treating the surface of the substrate coated with the Cr3C2-NiCr layer; (2) loading the pre-treated substrate into a vacuum chamber, vacuumizing and heating, and etching and cleaning the substrate under a bias to remove dust and other impurities attached to the surface; (3) after the etching, introducing a protective gas, first depositing a NiCr primer layer by opening the NiCr alloy target, then depositing a Ti transition layer by opening the Ti target, and finally depositing a carbon layer by opening the graphite target, and obtaining the TaC coating on the surface of the substrate after the coating deposition is completed.

3. A ball valve according to claim 1, wherein: The Cr3C2-NiCr coating is prepared by a high-velocity oxygen fuel spraying technology.

4. A ball valve according to claim 1, characterized in that: The Cr3C2-NiCr coating comprises a hard phase and a binder phase, the content of the hard phase is 70-80 wt%, and the content of the binder phase is 20-30 wt%.

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