A high-entropy alloy / ceramic composite coating and a preparation method thereof

Abstract

The application discloses a high-entropy alloy / ceramic composite coating and a preparation method thereof. The coating is prepared by spraying a high-entropy alloy / ceramic composite powder; the high-entropy alloy / ceramic composite powder is composed of 10-25% of high-entropy alloy CoCrNiAlTiNb, 20-35% of Cr2C3 and 40-70% of WC according to mass percentage; the high-entropy alloy CoCrNiAlTiNb is composed of Co:Cr:Ni:Al:Ti:Nb=20-45:10-25:10-25:5-10:5-10:1-5 according to atomic ratio. The composite coating has the advantages of low porosity, strong bonding force, air-erosion resistance, wear resistance, corrosion resistance and the like, and has unique advantages in solving air-erosion and wear of hydraulic equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of coating, and particularly relates to a high-entropy alloy / ceramic composite coating and a preparation method thereof. BACKGROUND

[0002] The cavitation and silt abrasion of a hydraulic turbine have been a key technical problem for long-life operation of the hydraulic turbine. In China, there are many rivers with silt, and about 30-40% of the hydraulic turbines have the problem of silt abrasion. Almost all the design operating conditions of the hydraulic turbines have the problem of cavitation. Since the Qingtongxia Hydropower Station is located on the main stream of the Yellow River with much silt, the operating environment is very poor, the silt is serious, and the cavitation is also serious. After the hydraulic turbine is operated for a period of time, the surface of the hydraulic turbine blade is subjected to the impact of the water flow with high silt content, and a large area of the surface is abraded. The silt abrasion and cavitation are superimposed on each other, and the surface damage of the hydraulic turbine blade is aggravated.

[0003] At present, the main technical means for solving the cavitation and silt abrasion at home and abroad mainly include the following: optimizing the hydraulic design, improving the toughness of the base material, coating an organic coating, carburizing and nitriding, surface shot peening nanocrystallization, and flame spraying, so as to improve the cavitation resistance and abrasion resistance of the hydraulic equipment. However, the above methods have poor effects.

[0004] The high-entropy alloy has a unique alloy phase structure and excellent performance. For example, the high-entropy alloy has high strength and hardness, good wear resistance, good plasticity and toughness, corrosion resistance, and the like. This provides a new idea for solving the cavitation of the blade of the hydraulic equipment. The present application combines the characteristics of the CoCrNiAlTiNb high-entropy alloy and WC and Cr2C3 ceramic powders, and uses oxygen-kerosene supersonic spraying to prepare a new surface modification technology. The prepared high-entropy alloy / ceramic composite coating has the advantages of low porosity, high bonding force, high cavitation resistance, high abrasion resistance, and the like. The high-entropy alloy / ceramic composite coating has unique advantages in solving the cavitation and abrasion of the hydraulic equipment. SUMMARY

[0005] The present application aims at the cavitation and silt abrasion of the flow components of the Qingtongxia Hydropower Station, and provides a high-entropy alloy / ceramic composite coating and a preparation method thereof, in particular a method for preparing the coating by atmospheric supersonic spraying. The composite coating has the advantages of cavitation resistance, silt abrasion resistance, corrosion resistance, and the like.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A high-entropy alloy / ceramic composite coating is prepared by spraying a high-entropy alloy / ceramic composite powder; the high-entropy alloy / ceramic composite powder is composed of 10-25% of high-entropy alloy CoCrNiAlTiNb, 20-35% of Cr2C3 and 40-70% of WC in terms of mass percentage; the high-entropy alloy CoCrNiAlTiNb is composed of Co:Cr:Ni:Al:Ti:Nb=20-45:10-25:10-25:5-10:5-10:1-5 in terms of atomic ratio.

[0008] Further, the spraying adopts an oxygen-kerosene supersonic spraying device.

[0009] The application further provides a preparation method of the high-entropy alloy / ceramic composite coating, comprising the following steps:

[0010] Step 1: proportionally configuring Co powder, Cr powder, Ni powder, Al powder, Ti powder, Nb powder, Cr2C3 and WC powder, and then obtaining the high-entropy alloy / ceramic composite powder by mechanical mixing method, spray drying method or gas atomization method;

[0011] Step 2: separately placing and laying the high-entropy alloy / ceramic composite powder, and drying at a temperature of 100-120℃ for 2-4 hours;

[0012] Step 3: cleaning the surface of the spraying substrate with acetone or alcohol, and drying at 50-60℃ to remove surface oil stains and dirt;

[0013] Step 4: adopting air power sandblasting to perform rust removal and roughening treatment on the surface of the spraying substrate, and selecting 20-30 mesh white or brown corundum for sandblasting treatment, the pressure of compressed air is 0.4-0.6 MPa, the sandblasting distance is 100-150 mm, and the sandblasting angle is 65°-90°;

[0014] Step 5: preparing the high-entropy alloy / ceramic composite coating by using an oxygen-kerosene supersonic spraying process.

[0015] Further, the high-entropy alloy / ceramic composite powder has a particle size of 5-35 μm.

[0016] Further, the high-entropy alloy / ceramic composite coating has a thickness of 0.10-0.5 mm.

[0017] Further, the parameters of the oxygen-kerosene supersonic spraying process are as follows:

[0018] The kerosene flow rate is 22-30 L / h, the kerosene pressure is 1.5-2.0 MPa, the oxygen flow rate is 840-950 L / min, the oxygen pressure is 1.7-2.0 MPa, the powder feeding rate is 80-100 g / min, the nitrogen flow rate is 10-15 L / min, the nitrogen pressure is 1.0-1.2 MPa, and the spraying distance is 350-400 mm.

[0019] The application solves the problem of performance decline of a coating caused by cavitation and silt abrasion of a flow part such as a water turbine and a pump.

[0020] The application has the following beneficial effects:

[0021] The application uses oxygen-kerosene supersonic spraying to prepare the high-entropy alloy / ceramic composite coating by continuously exploring the selection of high-entropy alloy / ceramic composite powder components and the coating preparation method.

[0022] The high-entropy alloy / ceramic coating is dense and uniform, the porosity is less than 0.5%, the microhardness is 750-1250 HV0.2, the cavitation resistance of the coating is 5-8 times that of the substrate under the same cavitation test parameters, the silt abrasion resistance of the coating is 10-17 times that of the substrate under the same silt abrasion test parameters, and the neutral salt spray corrosion resistance time of the coating is more than 72 h.

[0023] The preparation method of the high-entropy alloy / ceramic composite coating is reliable and stable in performance. DETAILED DESCRIPTION

[0024] In order to make the technical solutions and advantages of the application clearer and more understandable, the application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0025] The spraying substrate in the embodiments of the application can be ZG06Cr13Ni5Mo steel, ZG06Cr16Ni5Mo steel, ZG0Cr13Ni4Mo steel, ZG0Cr16Ni5Mo steel, etc.

[0026] Embodiment 1

[0027] (1) Co powder, Cr powder, Ni powder, Al powder, Ti powder, Nb powder, Cr2C3, WC powder are configured in the proportions; the specific ratio is as follows: in the mixture of CoCrNiAlTiNb, Cr2C3 and WC, the mass percentage of Cr2C3 is 20%, the mass percentage of WC is 65%, and the mass percentage of CoCrNiAlTiNb is 15%; in the CoCrNiAlTiNb powder: the atomic percentage of Co is 45%; the atomic percentage of Cr is 20%; the atomic percentage of Ni is 20%; the atomic percentage of Al is 7%; the atomic percentage of Ti is 5%; and the atomic percentage of Nb is 3%; the prepared powder is mixed by a mechanical mixing method to obtain a high-entropy alloy / ceramic composite powder;

[0028] (2) The high-entropy alloy / ceramic composite powder is placed separately and laid flat in a drying oven, and dried at a temperature of 100℃ for 3 hours;

[0029] (3) The surface of the spraying substrate is cleaned with acetone or alcohol, and placed in a drying oven at 50℃ to dry and remove surface oil stains and dirt;

[0030] (4) The surface of the spraying substrate is treated by air power sandblasting to remove rust and roughen, and 24-mesh white or brown corundum is selected for sandblasting treatment, the pressure of compressed air is 0.6 MPa, the sandblasting distance is 100-150 mm, and the sandblasting angle is 65°-90°;

[0031] (5) The high-entropy alloy / ceramic composite coating is prepared by using an oxygen-kerosene supersonic spraying process, wherein the parameters of the oxygen-kerosene supersonic spraying process are as follows: kerosene flow is 26 L / h, kerosene pressure is 1.8 MPa, oxygen flow is 880 L / min, oxygen pressure is 1.9 MPa, powder feeding rate is 85 g / min, nitrogen flow is 12 L / min, nitrogen pressure is 1.2 MPa, and spraying distance is 365 mm.

[0032] (6) The prepared high-entropy alloy / ceramic composite coating has a thickness of 0.32 mm, a porosity of 0.37%, and a microhardness of 1164 HV 0.2; the substrate and the coating layer have a bonding strength of 77 MPa; under the same cavitation erosion conditions, the cavitation erosion resistance of the coating layer is 6.57 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the cavitation erosion weight loss of the coating layer is 0.00081 g, and the cavitation erosion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.00532 g); the sand abrasion resistance of the coating layer is 13.5 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the sand abrasion weight loss of the coating layer is 0.01329 g, and the sand abrasion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.17948 g); and the neutral salt spray corrosion resistance time of the coating layer is more than 72 h.

[0033] Example 2

[0034] (1) Co powder, Cr powder, Ni powder, Al powder, Ti powder, Nb powder, Cr2C3, and WC powder are configured in the proportions as follows: in the mixture of CoCrNiAlTiNb, Cr2C3, and WC, the mass percentage of Cr2C3 is 20%, the mass percentage of WC is 60%, and the mass percentage of CoCrNiAlTiNb is 20%; in CoCrNiAlTiNb, the atomic percentage of Co is 41%; the atomic percentage of Cr is 25%; the atomic percentage of Ni is 18%; the atomic percentage of Al is 7%; the atomic percentage of Ti is 5%; and the atomic percentage of Nb is 4%; the configured powder is prepared into high-entropy alloy / ceramic composite powder by a spray drying method;

[0035] (2) The high-entropy alloy / ceramic composite powder is placed separately and flatly in a drying oven for drying, and the drying temperature is 120°C, and the drying time is 2 hours;

[0036] (3) The surface of the sprayed substrate is cleaned with acetone or alcohol, and is placed in a drying oven at 60°C for drying to remove surface oil stains and dirt;

[0037] (4) The surface of the sprayed substrate is treated for rust removal and roughening by an air power sandblasting method, and 20-30 mesh white or brown corundum is selected for sandblasting, the pressure of compressed air is 0.5 MPa, the sandblasting distance is 100-150 mm, and the sandblasting angle is 65°-90°;

[0038] (5) The high-entropy alloy / ceramic composite coating layer is prepared by an oxygen-kerosene supersonic spraying process, and the parameters of the oxygen-kerosene supersonic spraying process are as follows: the kerosene flow rate is 24 L / h, the kerosene pressure is 1.7 MPa, the oxygen flow rate is 860 L / min, the oxygen pressure is 1.7 MPa, the powder feeding rate is 85 g / min, the nitrogen flow rate is 12 L / min, the nitrogen pressure is 1.1 MPa, and the spraying distance is 380 mm.

[0039] (6) The prepared high-entropy alloy / ceramic composite coating has a thickness of 0.28 mm, a porosity of 0.43%, and a microhardness of 1207 HV 0.2 ; the substrate and coating have a bonding strength of 79 MPa; under the same cavitation conditions, the cavitation erosion resistance of the coating is 5.48 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the cavitation erosion weight loss of the coating is 0.00097 g, and the cavitation erosion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.00532 g); the sand abrasion resistance is 14.1 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the sand abrasion weight loss of the coating is 0.01277 g, and the sand abrasion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.17948 g); and the neutral salt spray corrosion resistance time is more than 72 h.

[0040] Example 3

[0041] (1) The Co powder, Cr powder, Ni powder, Al powder, Ti powder, Nb powder, Cr2C3, and WC powder are configured in the proportions as follows: in the mixture of CoCrNiAlTiNb, Cr2C3, and WC, the mass percentage of Cr2C3 is 25%, the mass percentage of WC is 60%, and the mass percentage of CoCrNiAlTiNb is 15%; in CoCrNiAlTiNb, the atomic percentage of Co is 42%; the atomic percentage of Cr is 21%; the atomic percentage of Ni is 20%; the atomic percentage of Al is 6%; the atomic percentage of Ti is 8%; and the atomic percentage of Nb is 3%.

[0042] (2) The high-entropy alloy / ceramic composite powder is placed flat and separately dried in a thermostat at a temperature of 100°C for 1.5 hours;

[0043] (3) The surface of the spraying substrate is cleaned with acetone or alcohol and dried in a thermostat at 60°C to remove surface oil stains and dirt;

[0044] (4) The surface of the spraying substrate is treated by air power sandblasting to remove rust and roughen, the sandblasting treatment uses 20-30 mesh white or brown corundum, the pressure of the compressed air during sandblasting is 0.4-0.6 MPa, the sandblasting distance is 100-150 mm, and the sandblasting angle is 65°-90°;

[0045] (5) The high-entropy alloy / ceramic composite coating is prepared by using the oxygen-kerosene supersonic spraying process, wherein the parameters of the oxygen-kerosene supersonic spraying process are as follows: kerosene flow is 26 L / h, kerosene pressure is 1.8 MPa, oxygen flow is 880 L / min, oxygen pressure is 1.8 MPa, powder feeding rate is 90 g / min, nitrogen flow is 13 L / min, nitrogen pressure is 1.2 MPa, and spraying distance is 370 mm;

[0046] (6) The prepared high-entropy alloy / ceramic composite coating has a thickness of 0.38 mm, a porosity of 0.47%, and a microhardness of 1255 HV 0.2 ; the substrate and the coating have a bonding strength of 82 MPa; under the same cavitation conditions, the cavitation erosion resistance of the coating is 7.39 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the cavitation erosion weight loss of the coating is 0.00072 g, and the cavitation erosion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.00532 g); the sand abrasion resistance of the coating is 13.87 times that of the substrate ZG06Cr13Ni5Mo stainless steel (the sand abrasion weight loss of the coating is 0.01294 g, and the sand abrasion weight loss of the substrate ZG06Cr13Ni5Mo stainless steel is 0.17948 g); and the neutral salt spray corrosion resistance of the coating is more than 72 h.

[0047] The above-described embodiments are only a preferred scheme of the present application, and do not limit the present application in any form, and other variants and modifications can be made without exceeding the technical scheme recorded in the claims.

Claims

1. A high-entropy alloy / ceramic composite coating, characterized in that, The high-entropy alloy / ceramic composite coating has a thickness of 0.10-0.5 mm and a porosity of less than 0.5%; the microhardness is 750-1250 HV0.2; the coating is formed by spraying the high-entropy alloy / ceramic composite powder; the high-entropy alloy / ceramic composite powder is composed of 10-25% of high-entropy alloy CoCrNiAlTiNb, 20-35% of Cr2C3 and 40-70% of WC in terms of mass percentage; the high-entropy alloy CoCrNiAlTiNb has an atomic ratio of Co:Cr:Ni:Al:Ti:Nb = 20-45:10-25:10-25:5-10:5-10:1-5; and the high-entropy alloy / ceramic composite powder has a particle size of 5-35 μm.

2. The high-entropy alloy / ceramic composite coating of claim 1, wherein, The spraying is performed by using an oxygen-kerosene supersonic spraying device.

3. A method of producing the high-entropy alloy / ceramic composite coating according to claim 1 or 2, characterized in that, The method comprises the following steps: Step 1: proportionally configuring Co powder, Cr powder, Ni powder, Al powder, Ti powder, Nb powder, Cr2C3 and WC powder, and then obtaining the high-entropy alloy / ceramic composite powder by mechanical mixing method, spray drying method or gas atomization method; Step 2: separately placing and laying the high-entropy alloy / ceramic composite powder, and drying at a temperature of 100-120 ℃ for 2-4 hours; Step 3: cleaning the surface of the spraying substrate with acetone or alcohol, and drying at 50-60 ℃ to remove surface oil stains and dirt; Step 4: performing rust removal and roughening treatment on the surface of the spraying substrate by using air power sand blasting process; Step 5: preparing the high-entropy alloy / ceramic composite coating by using oxygen-kerosene supersonic spraying process.

4. The production method according to claim 3, characterized by, The sand blasting process selects 20-30 mesh white or brown corundum, the pressure of compressed air during sand blasting is 0.4-0.6 MPa, the sand blasting distance is 100-150 mm, and the sand blasting angle is 65°-90°.

5. The preparation method according to claim 3, characterized in that, The parameters of the oxygen-kerosene supersonic spraying process are as follows: The kerosene flow rate is 22-30 L / h, the kerosene pressure is 1.5-2.0 MPa, the oxygen flow rate is 840-950 L / min, the oxygen pressure is 1.7-2.0 MPa, the powder feeding rate is 80-100 g / min, the nitrogen flow rate is 10-15 L / min, the nitrogen pressure is 1.0-1.2 MPa, and the spraying distance is 350-400 mm.