A friction-reducing wear-resistant coating suitable for molten salt corrosion working conditions and a preparation method thereof

Abstract

The present application relates to a kind of antifriction wear-resistant coating suitable for molten salt corrosion working condition, the coating is made of 88.5~93 wt.% of NiCr-20Cr3C2 powder, 1.5~5 wt.% of Al powder and 2~10 wt.% of Ag powder according to mass percentage, form Cr3C2, Cr7C3 Ceramic phase, Ni3Al phase and Ag lubricating phase.Simultaneously, the preparation method of the coating is also disclosed.The preparation method of the present application is simple and easy to operate, and the prepared coating has excellent antifriction, wear resistance and corrosion resistance in chloride molten salt environment, which is of great significance for the application of structural materials in actual chloride molten salt working condition, and can contribute to the stable operation of next-generation concentrated solar power plant.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and in particular to a friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions and its preparation method. Background Technology

[0002] To reduce dependence on fossil fuels and carbon dioxide emissions, the trend of developing renewable energy is becoming increasingly prominent. Among these technologies, concentrated solar power (CSP) combined with thermal energy storage is considered one of the most promising power generation technologies for the future. However, molten chlorides, which offer significant advantages in next-generation molten salt technology, are highly corrosive to structural materials at high temperatures, severely limiting their service life. Furthermore, impurities in molten chlorides cause severe wear on structural materials, and moving parts such as long-shaft pumps and bearings immersed in molten salt will be subjected to high-temperature friction as mechanical moving parts in CSP systems. Therefore, designing and preparing coatings with both excellent heat corrosion resistance and wear resistance is of great significance for the development of next-generation CSP technology.

[0003] Currently, widely used coating technologies include laser cladding, thermal spraying, plasma spraying, cold spraying, and electroplating. Among these, laser cladding technology is particularly suitable for surface strengthening of structural materials in chlorinated molten salt environments due to its advantages such as metallurgical bonding, low porosity, and dense structure. Patent CN104532231B discloses a method for preparing a Ni3Al / Cr3C2 composite coating using laser cladding technology. This coating exhibits a dense microstructure, high bonding strength, and good wear resistance. Patent CN117660908A prepares a pure nickel / gradient structure nickel-rhenium bilayer coating using laser cladding, which demonstrates excellent resistance to molten salt corrosion. Patent CN115852365A discloses a laser-clad high-hardness, corrosion-resistant, high-entropy alloy coating and its preparation method. The coating consists of 16.83%–18.95% Fe, 17.76%–20% Co, 15.67%–17.64% Cr, 17.68%–19.92% Ni, 4.07%–4.58% Al, and 18.92%–28% Nb. This coating exhibits high hardness and corrosion resistance.

[0004] In summary, existing coating technologies mostly focus on single wear resistance or corrosion resistance, neglecting the fact that the damage caused by the combined effects of thermal corrosion and wear is far greater than that caused by wear or corrosion alone. Therefore, there is an urgent need for a comprehensive coating that can resist both thermal corrosion and wear to meet the demands of harsh molten salt conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-performance friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions.

[0006] Another technical problem to be solved by the present invention is to provide a method for preparing the friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions.

[0007] To solve the above problems, the present invention provides a friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions, characterized in that: the coating is made of 88.5~93 wt.% NiCr-20Cr3C2 powder, 1.5~5 wt.% Al powder and 2~10 wt.% Ag powder by mass percentage, forming Cr3C2, Cr7C3 ceramic phase, Ni3Al phase and Ag lubricating phase.

[0008] The NiCr-20Cr3C2 powder, the Al powder, and the Ag powder are all spherical, with a purity ≥99.9% and a particle size of 20~50 μm.

[0009] The NiCr-20Cr3C2 powder refers to a mixed powder obtained by uniformly mixing NiCr-75Cr3C2 powder and NiCr powder at a mass ratio of 26.7:73.3.

[0010] The method for preparing a friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions, as described above, is characterized by: firstly, weighing according to the proportions; then mixing NiCr-20Cr3C2 powder, Al powder, and Ag powder by mechanical mixing for 3-6 hours and drying to obtain laser cladding powder; finally, loading the laser cladding powder into a powder feeder and performing laser cladding on the treated 304 stainless steel substrate surface to obtain the friction-reducing and wear-resistant coating.

[0011] The drying temperature is 100 ℃ and the time is 2 hours.

[0012] The conditions for laser cladding are as follows: laser power of 0.4~0.6 kW, defocusing amount of +2 mm, argon carrier gas volume of 10~13 L / min, scanning speed of 800~1200 mm / min, overlap rate of 40%~60%, and coating thickness of 530~580 μm.

[0013] The treated 304 stainless steel substrate surface is obtained by the following method: first, the 304 stainless steel block after wire cutting is ground to a roughness of less than 0.08 μm; then, it is ultrasonically cleaned in anhydrous alcohol; finally, it is dried in a drying oven at 90 ℃ to constant weight.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Compared with existing NiCr-Cr3C2-based coatings, the coating of the present invention makes full use of the high hardness of Cr3C2 and Cr7C3 ceramic phases, the friction-reducing and lubricating properties of Ag, and the chemical inertness of Al2O3 phase formed by the in-situ reaction of Al during friction, thereby realizing the design and preparation of a self-lubricating coating that is both wear-resistant and corrosion-resistant.

[0016] 2. The Cr7C3 and Cr3C2 phases in the coating of this invention provide excellent wear resistance, Al2O3 enhances the corrosion resistance to chlorinated molten salts, and the lubricating phase Ag provides friction reduction and lubrication. Simultaneously, by optimizing the coating composition and cladding parameters, a crack-free, metallurgically bonded, and densely structured coating was successfully prepared, effectively improving resistance to chlorinated molten salt corrosion.

[0017] 3. The coating prepared by this invention achieves an average friction coefficient of 0.12 and a wear rate of 9.8 × 10⁻⁶ in molten salt corrosive media. -6 mm 3 / Nm, compared to 304 stainless steel, the average coefficient of friction is reduced by 60% and the wear rate is reduced by 73%.

[0018] 4. The preparation method of this invention is simple and easy to implement. The prepared coating exhibits good friction reduction and wear resistance in molten salt corrosion media, which is of great significance for the application of structural materials under actual chlorinated molten salt conditions and can contribute to the stable operation of the next generation of concentrated solar power plants. Attached Figure Description

[0019] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] Figure 1 The image shows the microstructure of the cross-section of the 93(NiCr-20Cr3C2)-5Al-2Ag laser cladding coating prepared in Example 1 of this invention.

[0021] Figure 2 The X-ray diffraction pattern of the 88.5(NiCr-20Cr3C2)-1.5Al-10Ag laser cladding coating prepared in Example 3 of the present invention.

[0022] Figure 3 The friction coefficient of the 92(NiCr-20Cr3C2)-3Al-5Ag laser cladding coating prepared in Example 2 of this invention and in Example 4 in a high-temperature molten salt environment. Detailed Implementation

[0023] A friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions is provided. The coating is made of 88.5~93 wt.% NiCr-20Cr3C2 powder, 1.5~5 wt.% Al powder and 2~10 wt.% Ag powder by mass percentage (g), forming Cr3C2, Cr7C3 ceramic phase, Ni3Al phase and Ag lubricating phase.

[0024] Among them, NiCr-20Cr3C2 powder, Al powder and Ag powder are all spherical, with a purity of ≥99.9% and a particle size of 20~50μm.

[0025] NiCr-20Cr3C2 powder refers to a mixed powder obtained by uniformly mixing NiCr-75Cr3C2 powder and NiCr powder at a mass ratio of 26.7:73.3 (g / g).

[0026] A method for preparing a friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions:

[0027] First, weigh the powders according to the specified ratio. Then, mix the NiCr-20Cr3C2 powder, Al powder, and Ag powder mechanically for 3-6 hours to obtain a mixed powder. Place the mixed powder in a vacuum drying oven at 100 °C for 2 hours to obtain the powder for laser cladding. Finally, load the powder for laser cladding into a powder feeder and perform laser cladding on the treated 304 stainless steel substrate to obtain a friction-reducing and wear-resistant coating.

[0028] The conditions for laser cladding are as follows: laser power is 0.4~0.6 kW, defocusing amount is +2 mm, argon carrier gas volume is 10~13 L / min, scanning speed is 800~1200 mm / min, overlap rate is 40%~60%, and coating thickness is 530~580 μm.

[0029] The treated 304 stainless steel substrate surface is obtained by the following method: First, the 304 stainless steel block after wire cutting is ground to a roughness of less than 0.08 μm; then, it is ultrasonically cleaned in anhydrous alcohol; finally, it is dried in a drying oven at 90 ℃ to constant weight.

[0030] Example 1

[0031] A friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions is provided, which is made of 93 g of NiCr-20Cr3C2 powder, 5 g of Al powder and 2 g of Ag powder.

[0032] Its preparation method:

[0033] First, the powders were weighed according to the specified proportions. Then, NiCr-20Cr3C2 powder, Al powder, and Ag powder were mechanically mixed for 3-6 hours to obtain a mixed powder. The mixed powder was then placed in a vacuum drying oven and dried at 100 °C for 2 hours to obtain the laser cladding powder. Finally, the laser cladding powder was loaded into a powder feeder and laser cladding was performed on the treated 304 stainless steel substrate. The cladding conditions were: laser power of 0.6 kW, defocusing distance of +2 mm, argon carrier gas flow rate of 10 L / min, scanning speed of 1000 mm / min, overlap rate of 55%, and coating thickness of 550 μm.

[0034] The cross-sectional microstructure of the coating is as follows Figure 1 As shown. From Figure 1 It can be seen that the coating is free of cracks and pores and has a dense structure.

[0035] Performance testing was conducted on Example 1:

[0036] [Hardness] The hardness was tested using a Vickers hardness tester. The test conditions were: a load of 10 N and a loading time of 10 s. The hardness test results are shown in Table 1.

[0037] [Average Coefficient of Friction] The friction was tested using a high-temperature vacuum ball-and-disc friction testing machine in a vacuum environment of 700 ℃ and <7 Pa, and in a molten salt medium of MgCl2 / NaCl (42 / 58 mol%). The friction test conditions were: normal load of 10 N, sliding speed of 0.1 m / s, sliding radius of 3.5 mm, and total sliding distance of 224 m. The average coefficient of friction is shown in Table 1.

[0038] [Wear Rate] The wear volume of the wear trajectory was measured using a 3D optical surface profilometer. The wear rate test results are shown in Table 1.

[0039] Table 1 Test Results

[0040]

[0041] Example 2

[0042] A friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions is provided, which is made of 92 g of NiCr-20Cr3C2 powder, 3 g of Al powder and 5 g of Ag powder.

[0043] Its preparation method:

[0044] First, the powders were weighed according to the specified proportions. Then, NiCr-20Cr3C2 powder, Al powder, and Ag powder were mechanically mixed for 3-6 hours to obtain a mixed powder. The mixed powder was then placed in a vacuum drying oven and dried at 100 °C for 2 hours to obtain the powder for laser cladding. Finally, the laser cladding powder was loaded into a powder feeder and laser cladding was performed on the treated 304 stainless steel substrate. The cladding conditions were: laser power of 0.5 kW, defocusing distance of +2 mm, argon carrier gas flow rate of 12 L / min, scanning speed of 800 mm / min, overlap rate of 50%, and coating thickness of 530 μm.

[0045] Performance testing was conducted on Example 2:

[0046] [Hardness] The hardness was tested using a Vickers hardness tester. The test conditions were: a load of 10 N and a loading time of 10 s. The hardness test results are shown in Table 2.

[0047] [Average Coefficient of Friction] The average coefficient of friction was tested using a high-temperature vacuum ball-and-disc friction testing machine in a vacuum environment of 700 ℃ and <7 Pa, and in a molten salt medium of MgCl2 / NaCl (42 / 58 mol%). The friction test conditions were: normal load of 10 N, sliding speed of 0.1 m / s, sliding radius of 3.5 mm, and total sliding distance of 224 m. The coefficient of friction curve of this coating is shown below. Figure 3 As shown in Table 2, the average coefficient of friction is also shown.

[0048] [Wear Rate] The wear volume of the wear trajectory was measured using a 3D optical surface profilometer. The wear rate test results are shown in Table 2.

[0049] Table 2 Test Results

[0050]

[0051] Example 3

[0052] A friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions is provided, which is made of 88.5 g of NiCr-20Cr3C2 powder, 1.5 g of Al powder and 10 g of Ag powder.

[0053] Its preparation method:

[0054] First, the powders were weighed according to the specified proportions. Then, NiCr-20Cr3C2 powder, Al powder, and Ag powder were mechanically mixed for 3-6 hours to obtain a mixed powder. The mixed powder was then placed in a vacuum drying oven and dried at 100 °C for 2 hours to obtain the powder for laser cladding. Finally, the laser cladding powder was loaded into a powder feeder and laser cladding was performed on the treated surface of a 304 stainless steel substrate. The cladding conditions were as follows: laser power of 0.4 kW, defocusing distance of +2 mm, argon carrier gas flow rate of 13 L / min, scanning speed of 1200 mm / min, overlap rate of 60%, and coating thickness of 580 μm.

[0055] The X-ray diffraction pattern of the coating is as follows Figure 2 As shown. From Figure 2 It can be seen that a laser cladding coating composed of Cr3C2, Cr7C3, Al2O3, Ag, (Ni, Fe) and Ni3Al was successfully prepared.

[0056] Performance testing was conducted on Example 3:

[0057] [Hardness] The hardness was tested using a Vickers hardness tester. The test conditions were: a load of 10 N and a loading time of 10 s. The hardness test results are shown in Table 3.

[0058] [Average Coefficient of Friction] The friction was tested using a high-temperature vacuum ball-and-disc friction testing machine in a vacuum environment of 700 ℃ and <7 Pa, and in a molten salt medium of MgCl2 / NaCl (42 / 58 mol%). The friction test conditions were: normal load of 10 N, sliding speed of 0.1 m / s, sliding radius of 3.5 mm, and total sliding distance of 224 m. The average coefficient of friction is shown in Table 3.

[0059] [Wear Rate] The wear volume of the wear trajectory was measured using a 3D optical surface profilometer. The wear rate test results are shown in Table 3.

[0060] Table 3 Test Results

[0061]

[0062] Example 4

[0063] A 304 stainless steel block was used as a control sample.

[0064] Performance testing was conducted on Example 4:

[0065] [Hardness] The hardness was tested using a Vickers hardness tester. The test conditions were: a load of 10 N and a loading time of 10 s. The hardness test results are shown in Table 4.

[0066] [Average Coefficient of Friction] The friction coefficient was tested using a high-temperature vacuum ball-and-disc friction testing machine in a vacuum environment of 700 °C and <7 Pa, and in a molten salt medium of MgCl2 / NaCl (42 / 58 mol%). The friction test conditions were: normal load of 10 N, sliding speed of 0.1 m / s, sliding radius of 3.5 mm, and total sliding distance of 224 m. The friction coefficient curve of Example 4 is shown below. Figure 3 As shown in Table 4, the average coefficient of friction is also shown.

[0067] [Wear Rate] The wear volume of the wear trajectory was measured using a 3D optical surface profilometer. The wear rate test results are shown in Table 4.

[0068] Table 4 Test Results

[0069]

[0070] Tables 1-4 and Figure 3 The results show that by optimizing the coating component content and preparation process parameters, excellent tribological properties under molten salt corrosion conditions were achieved while maintaining good hardness; the average coefficient of friction was as low as 0.12, and the wear rate was 9.8 × 10⁻⁶. -6 mm 3 / Nm, with a hardness of 558 HV.

Claims

1. A friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions, characterized in that: The coating, by mass percentage, is made of 88.5–93 wt.% NiCr-20Cr3C2 powder, 1.5–5 wt.% Al powder, and 2–10 wt.% Ag powder, forming Cr3C2, Cr7C3 ceramic phases, Ni3Al phase, and Ag lubricating phase. The NiCr-20Cr3C2 powder refers to a mixed powder obtained by uniformly mixing NiCr-75Cr3C2 powder and NiCr powder at a mass ratio of 26.7:73.

3. The preparation method of the coating is as follows: first, weigh according to the proportions; then, mix the NiCr-20Cr3C2 powder, Al powder, and Ag powder mechanically for 3–6 hours and dry to obtain the laser cladding powder; finally, load the laser cladding powder into a powder feeder and perform laser cladding on the treated 304 stainless steel substrate surface to obtain a friction-reducing and wear-resistant coating.

2. The friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions as described in claim 1, characterized in that: The NiCr-20Cr3C2 powder, the Al powder, and the Ag powder are all spherical, with a purity ≥99.9% and a particle size of 20~50 μm.

3. The friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions as described in claim 1, characterized in that: The drying temperature is 100 ℃ and the time is 2 hours.

4. The friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions as described in claim 1, characterized in that: The conditions for laser cladding are as follows: laser power of 0.4~0.6 kW, defocusing amount of +2 mm, argon carrier gas volume of 10~13 L / min, scanning speed of 800~1200 mm / min, overlap rate of 40%~60%, and coating thickness of 530~580 μm.

5. The friction-reducing and wear-resistant coating suitable for molten salt corrosion conditions as described in claim 1, characterized in that: The treated 304 stainless steel substrate surface is obtained by the following method: first, the 304 stainless steel block after wire cutting is ground to a roughness of less than 0.08 μm; then, it is ultrasonically cleaned in anhydrous alcohol; finally, it is dried in a drying oven at 90 ℃ to constant weight.

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