A wear-resistant and friction-reducing coating material for high-temperature molten salt environments and its preparation method

Abstract

This invention relates to a wear-resistant and friction-reducing coating material for high-temperature molten salt environments. The coating material has the composition xCr3C2-yNiCr-zAl-mY, where 50≤x≤70, 27.0≤y≤48.5, 1≤z≤2, and 0.5≤m≤1. The invention also discloses a method for preparing this coating material. By controlling the composition, microstructure, and preparation process of the coating material, this invention obtains a highly reliable coating material with few crack defects that exhibits wear resistance and friction reduction in high-temperature molten salt environments. This material possesses excellent mechanical properties and wear resistance and friction reduction performance in high-temperature molten salt environments, making it suitable for application under extreme and harsh conditions such as high-temperature molten salt environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature molten salt, and particularly relates to a coating material with anti-wear and friction-reducing properties in a high-temperature molten salt environment and a preparation method thereof. BACKGROUND

[0002] Molten salt has the advantages of high use temperature, high specific heat capacity, high convective heat transfer coefficient, low viscosity, low saturated vapor pressure, low cost, good thermal stability, and heat storage and heat transfer capacity, and is an ideal heat storage and heat transfer medium for solar thermal power generation. Fluoride salt has small viscosity, large latent heat, good thermal migration characteristics and high use temperature when molten, and has a wide application prospect in the field of solar thermal power stations. At present, the metal materials resistant to high-temperature molten salt mainly depend on imports, and the lack of domestic high-performance materials is still a bottleneck problem restricting the light-to-electricity conversion efficiency, cost and large-scale commercial application of solar thermal power stations. Among them, the core key metal components of the concentrated solar system in the high-temperature molten salt medium, such as the heat absorber, the heat accumulator and the transmission pipeline, will all be severely corroded and worn, directly affecting the operation safety and power generation efficiency of the solar thermal power station. Therefore, developing a coating material with anti-wear and friction-reducing properties in a high-temperature molten salt environment plays a crucial role in the efficient and safe operation of solar thermal power stations and the industrial development thereof.

[0003] The cermet coating Cr3C2-NiCr has high hardness, stable chemical properties, and good corrosion resistance and wear resistance. At present, the Cr3C2-NiCr cermet coating can be prepared by laser cladding, flame spraying, plasma spraying and explosion spraying, but the coating prepared by flame spraying, plasma spraying and explosion spraying has low bonding force and cannot meet the service requirements under high-temperature molten salt working conditions. The coating prepared by laser cladding usually has metallurgical bonding with the substrate material and has good bonding force. However, the Cr3C2-NiCr cermet coating prepared by laser cladding will produce a large number of cracks due to large thermal stress, which seriously affects the service life and reliability of the coating. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a coating material with anti-wear and friction-reducing properties in a high-temperature molten salt environment and few crack defects.

[0005] Another technical problem to be solved by the present application is to provide a preparation method of the coating material with anti-wear and friction-reducing properties in a high-temperature molten salt environment.

[0006] To solve the above problems, the coating material with anti-wear and friction-reducing properties in a high-temperature molten salt environment has the following characteristics: the coating material is composed of xCr3C2-yNiCr-zAl-mY, 50≤x≤70, 27.0≤y≤48.5, 1≤z≤2, and 0.5≤m≤1.

[0007] The preparation method of a high-temperature molten salt environment anti-wear and friction-reducing coating material as described above is characterized by: placing 67-93.3% of 75Cr3C2-25NiCr, 3.7-31.5% of NiCr, 1%-2% of Al and 0.5%-1% of Y powder into a low-energy ball mill, with a ball-to-material ratio of 0.2:1 to 0.6:1, a rotation speed of 150-250 r / min, a ball milling time of 4-8 h, using a polymer jar and silicon nitride balls; after uniform mixing, drying and sieving to obtain a mixed powder with a particle size of 25-45 μm; using a synchronous powder feeding method and an ultra-high-speed laser cladding device, rapidly melting and solidifying the uniformly mixed cladding powder on the surface of a pretreated stainless steel substrate, and then air-cooling the clad stainless steel substrate to room temperature, thereby obtaining a high-temperature molten salt environment anti-wear and friction-reducing coating material on the surface of the stainless steel substrate.

[0008] In the ultra-high-speed laser cladding process, the laser is an Nd:YAG semiconductor fiber laser with a laser power of 500-1000 W and an overlap rate of 40-60%; the laser moving speed is 600-1000 mm / min; the powder carrier gas is argon with a flow rate of 8-10 L / min and a powder feeding speed of 0.8-1.2 r / min.

[0009] The pretreated stainless steel substrate surface refers to the surface of the stainless steel substrate after sandblasting and cleaning with anhydrous ethanol.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1. By controlling the composition, microstructure and preparation process of the coating material, this invention has for the first time obtained a highly reliable coating material with few crack defects that has wear resistance and friction reduction in a high-temperature molten salt environment.

[0012] 2. This invention, for the first time, modulates the composition of a coating material of xCr3C2-yNiCr-zAl-mY (50≤x≤70, 27.0≤y≤48.5, 1≤z≤2, 0.5≤m≤1) and selects an appropriate preparation process to induce a reaction during high-temperature preparation and cooling, thereby reducing thermal stress. The aim is to obtain a highly reliable coating material with few crack defects and wear-resistant and friction-reducing properties in a high-temperature molten salt environment. Figure 2 It can be seen that the coating material prepared by the present invention does not have obvious crack defects.

[0013] 3. This invention, through the optimization of the composition and preparation process of the metal-ceramic coating, can obtain a coating material with excellent mechanical and tribological properties. The prepared coating material has a hardness of up to 12.2 GPa, and its coefficient of friction and wear rate are as low as 0.08 and 10, respectively, at 600℃. -6mm 3 The coating material has a hardness on the order of Nm. Compared to the uncoated stainless steel substrate, the prepared coating material has a hardness that is 4.5 times greater, and a wear rate and friction coefficient that are reduced by an order of magnitude and more than twice, respectively. This achieves a balance between the mechanical and tribological properties of the metal-ceramic coating material and high reliability under operating conditions.

[0014] Mechanical properties

[0015] The hardness of the material was tested using a Vickers microhardness tester under the following conditions: a load of 300 g and a loading duration of 10 s. The test results showed that the hardness of the prepared coating material was 6.5–12.2 GPa at room temperature.

[0016]

Vacuum Tribological Properties

[0017] Friction and wear tests were conducted using a high-temperature vacuum testing machine (GHT-1000E). The molten salt was FLiNaK, the paired spheres were Al2O3 ceramic, the load was 5 N, the sliding linear velocity was 0.10 m / s, the friction radius was 4 mm, the stroke was 200 m, and the test temperature was 600 ℃. The coefficient of friction and wear rate were the average of three tests. The experimental results show that the prepared cermet coating material has excellent tribological properties at 600 ℃: the coefficient of friction and wear rate are as low as 0.08 and 2.1 × 10⁻⁶, respectively. -6 mm 3 / Nm (as shown in Tables 1-2).

[0018] Table 1: Coefficients of friction between the metal-ceramic coating and the stainless steel substrate material of this invention and the Al2O3 ceramic sphere pair.

[0019]

[0020] Table 2: Wear rate of the metal-ceramic coating and stainless steel substrate material of the present invention paired with Al2O3 ceramic balls

[0021]

[0022] 4. The preparation process of this invention is simple. By adjusting the formula and process parameters, the microstructure and properties of the material can be controlled. The resulting coating material can be used in extreme and harsh conditions such as high temperature molten salt. Attached Figure Description

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1X-ray diffraction patterns of the 50Cr3C2-48.5NiCr-1Al-0.5Y and 70Cr3C2-27NiCr-2Al-1Y cermet coatings prepared in Examples 1 and 3 of this invention.

[0025] Figure 2 The image shows the microstructure of the 60Cr3C2-37.75NiCr-1.5Al-0.75Y cermet coating prepared in Example 2 of this invention.

[0026] Figure 3 The friction coefficient of the 70Cr3C2-27NiCr-2Al-1Y cermet coating prepared in Example 3 of this invention at 600℃. Detailed Implementation

[0027] A wear-resistant and friction-reducing coating material for high-temperature molten salt environments, the coating material having the composition xCr3C2-yNiCr-zAl-mY, 50≤x≤70, 27.0≤y≤48.5, 1≤z≤2, and 0.5≤m≤1.

[0028] The preparation method is as follows: 67-93.3% of 75Cr3C2-25NiCr, 3.7-31.5% of NiCr, 1%-2% of Al, and 0.5%-1% of Y powder are placed in a low-energy ball mill at a mass percentage (g / g). The ball-to-material ratio is 0.2:1 to 0.6:1, the rotation speed is 150-250 r / min, and the ball milling time is 4-8 h. The grinding jar is a polymer jar, and the grinding balls are silicon nitride balls. After uniform mixing, the mixture is dried and sieved to obtain a mixed powder with a particle size of 25-45 μm. Using a synchronous powder feeding method, the uniformly mixed cladding powder is rapidly fused onto the surface of a pretreated stainless steel substrate using an ultra-high-speed laser cladding device. The clad stainless steel substrate is then air-cooled to room temperature, thus obtaining a high-temperature molten salt environment anti-wear and friction-reducing coating material on the surface of the stainless steel substrate.

[0029] In the ultra-high-speed laser cladding process, the laser is an Nd:YAG semiconductor fiber laser with a laser power of 500–1000 W and an overlap rate of 40–60%; the laser moving speed is 600–1000 mm / min; the powder carrier gas is argon with a flow rate of 8–10 L / min and a powder feeding speed of 0.8–1.2 r / min.

[0030] Pre-treated stainless steel substrate surface refers to the process of sandblasting and cleaning with anhydrous ethanol to remove oxides and surface stains from the stainless steel substrate surface.

[0031] Example 1: A wear-resistant and friction-reducing coating material for high-temperature molten salt environments, the coating material having the composition of 50Cr3C2-48.5NiCr-1Al-0.5Y.

[0032] The preparation method is as follows: 67 g of 75Cr3C2-25NiCr, 31.5 g of NiCr, 1 g of Al and 0.5 g of Y powder are placed in a low-energy ball mill with a ball-to-material ratio of 0.6:1, a rotation speed of 150 r / min and a ball milling time of 8 h. The grinding jar is a polymer jar and the grinding balls are silicon nitride balls. After uniform mixing, the mixture is dried and sieved to obtain a mixed powder with a particle size of 25~45 μm. Using a synchronous powder feeding method, the uniformly mixed cladding powder is rapidly fused onto the surface of a pretreated stainless steel substrate using an ultra-high-speed laser cladding device. The clad stainless steel substrate is then air-cooled to room temperature, thus obtaining a high-temperature molten salt environment anti-wear and friction-reducing coating material on the surface of the stainless steel substrate.

[0033] In the ultra-high-speed laser cladding process, the laser is an Nd:YAG semiconductor fiber laser with a laser power of 1000 W and an overlap rate of 40%; the laser moving speed is 600 mm / min; the powder carrier gas is argon with a flow rate of 8 L / min and a powder feeding speed of 0.8 r / min.

[0034] Pre-treated stainless steel substrate surface refers to the process of sandblasting and cleaning with anhydrous ethanol to remove oxides and surface stains from the stainless steel substrate surface.

[0035] The phase composition of the material is as follows Figure 1 As shown. By Figure 1 It can be seen that a Cr3C2-NiCr cermet coating was successfully prepared.

[0036] Example 2: A wear-resistant and friction-reducing coating material for high-temperature molten salt environments, the coating material having the composition of 60Cr3C2-37.75NiCr-1.5Al-0.75Y.

[0037] The preparation method is as follows: 80 g of 75Cr3C2-25NiCr, 17.75 g of NiCr, 1.5 g of Al and 0.75 g of Y powder are placed in a low-energy ball mill with a ball-to-material ratio of 0.4:1, a rotation speed of 200 r / min and a ball milling time of 6 h. The grinding jar is a polymer jar and the grinding balls are silicon nitride balls. After uniform mixing, the mixture is dried and sieved to obtain a mixed powder with a particle size of 25~45 μm. Using a synchronous powder feeding method, the uniformly mixed cladding powder is rapidly fused onto the surface of a pretreated stainless steel substrate using an ultra-high-speed laser cladding device. The clad stainless steel substrate is then air-cooled to room temperature, thus obtaining a high-temperature molten salt environment anti-wear and friction-reducing coating material on the surface of the stainless steel substrate.

[0038] In the ultra-high-speed laser cladding process, the laser is an Nd:YAG semiconductor fiber laser with a laser power of 700 W and an overlap rate of 50%; the laser moving speed is 800 mm / min; the powder carrier gas is argon with a flow rate of 9 L / min and a powder feeding speed of 1.0 r / min.

[0039] Pre-treated stainless steel substrate surface refers to the process of sandblasting and cleaning with anhydrous ethanol to remove oxides and surface stains from the stainless steel substrate surface.

[0040] The microstructure of the material is as follows Figure 2 As shown. By Figure 2 It can be seen that the prepared metal-ceramic coating material does not have obvious defects such as cracks.

[0041] Example 3: A wear-resistant and friction-reducing coating material for high-temperature molten salt environments, the coating material having the composition 70Cr3C2-27NiCr-2Al-1Y.

[0042] The preparation method is as follows: 93.3 g of 75Cr3C2-25NiCr, 3.7 g of NiCr, 2 g of Al and 1 g of Y powder are placed in a low-energy ball mill with a ball-to-material ratio of 0.2:1, a rotation speed of 250 r / min and a ball milling time of 4 h. The grinding jar is a polymer jar and the grinding balls are silicon nitride balls. After uniform mixing, the mixture is dried and sieved to obtain a mixed powder with a particle size of 25~45 μm. Using a synchronous powder feeding method, the uniformly mixed cladding powder is rapidly fused onto the surface of a pretreated stainless steel substrate using an ultra-high-speed laser cladding device. The clad stainless steel substrate is then air-cooled to room temperature, thus obtaining a high-temperature molten salt environment anti-wear and friction-reducing coating material on the surface of the stainless steel substrate.

[0043] In the ultra-high-speed laser cladding process, the laser is an Nd:YAG semiconductor fiber laser with a laser power of 500 W and an overlap rate of 60%; the laser moving speed is 1000 mm / min; the powder carrier gas is argon with a flow rate of 10 L / min and a powder feeding speed of 1.2 r / min.

[0044] Pre-treated stainless steel substrate surface refers to the process of sandblasting and cleaning with anhydrous ethanol to remove oxides and surface stains from the stainless steel substrate surface.

[0045] The phase composition of the material is as follows Figure 1 As shown. By Figure 1 It can be seen that a Cr3C2-NiCr cermet coating was successfully prepared. The friction coefficient of this material in a molten salt environment at 600℃ is as follows: Figure 3 As shown. By Figure 3It can be seen that the prepared coating material has excellent friction reduction properties at 600℃, with a friction coefficient as low as about 0.08.

Claims

1. A coating material for high temperature molten salt environment with anti-wear and friction reduction, characterized in that: The coating material is xCr3C2-yNiCr-zAl-mY, 50<=x<=70, 27.0<=y<=48.5, 1<=z<=2, 0.5<=m<=1; the preparation method is: according to mass percentage, 67~93.3% of 75Cr3C2-25NiCr, 3.7~31.5% of NiCr, 1%~2% of Al and 0.5%~1% of Y powder are placed in a low-energy ball mill, the ball-to-material ratio is 0.2:1~0.6:1, the rotating speed is 150~250 r / min, the ball milling time is 4~8 h, the mill pot is a polymer pot, and the milling ball is a silicon nitride ball; after mixing uniformly, drying and sieving, the mixed powder with a particle size of 25~45 μm is obtained; by using a synchronous powder feeding mode, the mixed uniformly cladding powder is rapidly melted on the surface of a pretreated stainless steel substrate by using an ultra-high-speed laser cladding equipment, the cladded stainless steel substrate is air-cooled to room temperature, and a coating material with high-temperature molten salt environment resistance and wear resistance and friction reduction is obtained on the surface of the stainless steel substrate; in the process of the ultra-high-speed laser cladding preparation, the laser is a semiconductor fiber laser of Nd:YAG, the laser power is 500~1000 W, the overlap rate is 40~60%, the laser moving speed is 600~1000 mm / min, the powder carrying gas is argon, the gas flow is 8~10 L / min, and the powder feeding rotating speed is 0.8~1.2 r / min.

2. A coating material for high temperature molten salt environment for wear resistance and friction reduction as claimed in claim 1, wherein: The pretreated stainless steel substrate surface refers to the surface of the stainless steel substrate after sand blasting treatment and anhydrous ethanol cleaning.

Images