A method for electric arc additive remanufacturing repair of LNG cryogenic submerged pump sliding bearing

Abstract

The application belongs to the technical field of high-entropy alloy additive repair, and more particularly relates to a method for electric arc additive remanufacturing repair of a sliding bearing of an LNG cryogenic immersed pump. x Cu y Al z Z w The high-entropy alloy with a general formula of (CrFeMnNi) The application effectively improves the stability and service life of the LNG cryogenic immersed pump bearing, is favorable for reducing the maintenance time and use cost, and has the advantages of simple operation process of the electric arc additive remanufacturing repair, high hardness and strong low-temperature wear resistance of the sliding bearing after the repair remanufacturing, great application potential in a lubricating environment of liquid oxygen, liquid nitrogen, liquefied natural gas and the like, and effective extension of the service life of the LNG cryogenic immersed pump.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy alloy additive repair technology, and more specifically relates to an arc additive remanufacturing repair method for sliding bearings of LNG cryogenic submersible pumps. Background Technology

[0002] Liquefied natural gas (LNG), as a clean energy source, is receiving increasing attention in today's climate of promoting energy conservation and environmental protection. LNG cryogenic submersible pumps play a crucial role in the transportation and transfer of LNG. However, the ball bearings commonly used in LNG cryogenic submersible pumps have a short lifespan under cryogenic conditions. After a short period of operation, the ball bearings become unstable and fail, severely impacting the efficiency of LNG transportation and transfer, as well as the safety of the equipment.

[0003] High-entropy alloys possess excellent low-temperature mechanical properties and wear resistance, making them highly valued in materials science and engineering. Traditional alloys often contain only one or two main metallic components. The prevailing notion was that adding more metals would lead to embrittlement, but high-entropy alloys differ from these, containing multiple metals without becoming brittle. High-entropy alloys exhibit superior mechanical properties, primarily high strength and high hardness. These characteristics enable them to perform exceptionally well in various engineering applications, maintaining stability in corrosive environments and extremely low-temperature conditions. Their high wear resistance makes them suitable for applications requiring high wear resistance. Laser repair and remanufacturing of sliding bearings is of great significance for achieving a low-carbon economic development. Summary of the Invention

[0004] The purpose of this invention is to provide a method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, in order to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is to provide a high-entropy alloy for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, wherein the general formula of the high-entropy alloy is: (CrFeMnNi). x Cu y Al z Z w ;

[0007] Where Z is selected from Si, Ti, Ca or RE; x is 0.550-0.800, y is 0.150-0.300, z is 0.100-0.150, w is 0.005-0.05, and the sum of x, y, z and w is 1.

[0008] The second technical solution of the present invention provides an application of the above-mentioned high-entropy alloy in the arc additive remanufacturing repair or preparation of bearing bushes for sliding bearings.

[0009] The third technical solution of this invention: provides a method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0010] The bearing substrate of the sliding bearing of the LNG cryogenic submersible pump is pretreated to obtain a pretreated component;

[0011] Prepare high-entropy alloy raw materials according to the general formula of the above high-entropy alloys, for later use;

[0012] The high-entropy alloy raw material is processed by arc additive manufacturing to obtain an arc-added processed component.

[0013] The arc additive manufacturing process involves sequentially undergoing high-temperature short-time annealing, first low-temperature cooling, multi-pass medium-temperature annealing, second low-temperature cooling, cryogenic treatment, rough machining, and fine machining to obtain the repaired bearing component.

[0014] Furthermore, the pretreatment step includes: the bearing substrate is successively polished, cleaned, and preheated to obtain a pretreated component.

[0015] Optionally, the cleaning may be performed using acetone or ethanol.

[0016] Optionally, the preheating temperature is 100-200℃.

[0017] In the pretreatment step, wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the surface of the bearing bush are removed by grinding.

[0018] Furthermore, the high-entropy alloy raw material includes elemental powders and / or intermediate alloy powders.

[0019] The high-entropy alloy raw materials include a variety of Mn powder, Fe powder, Cr powder, Ni powder, Cu powder, Al powder, Ca powder, Si powder, Ti powder, Al-Ce powder, Al-La powder, Al-Y powder, aluminum-manganese alloy powder, aluminum-iron alloy powder, aluminum-chromium alloy powder, aluminum-nickel alloy powder, aluminum-copper alloy powder, aluminum-calcium alloy powder, aluminum-silicon alloy powder, and aluminum-titanium alloy powder, to support the general formula of the above-mentioned high-entropy alloy.

[0020] Furthermore, the process parameters for the electric arc additive manufacturing are as follows: pulse energy of 0.5-2.5J, pulse frequency of 5-25Hz, operating current of 40-65A, and feed speed of 150-500mm / min; the protective gas is Ar, and the flow rate is 10-20L / min.

[0021] Furthermore, in the arc additive manufacturing process, adjacent cladding materials are rotated by 15°-45°.

[0022] Stress concentration can be avoided by rotating the device 15°–45°.

[0023] Furthermore, the high-temperature short-time annealing is performed using high-frequency induction heating.

[0024] Optionally, the process parameters for the high-frequency induction heating are: power of 10-16KW, heating rate of 15-50℃ / s, heating temperature of 950-1100℃, induction heating time of 10-60s, and frequency range of 200-250KHz.

[0025] Furthermore, the first cryogenic cooling is performed in a liquid nitrogen bath or a dry ice bath.

[0026] In this invention, the first low-temperature cooling is rapid cooling to liquid nitrogen temperature or dry ice temperature.

[0027] This invention enhances lattice distortion energy and increases the driving force for phase transition during multi-pass intermediate-temperature annealing by rapidly cooling at low temperatures (first low-temperature cooling).

[0028] Furthermore, the multi-pass intermediate-temperature annealing is carried out in a vacuum resistance furnace or a gas-protected resistance furnace.

[0029] By using multi-pass medium-temperature annealing to reduce the high internal stress in the repair and remodeling area, the formation of nano-precipitates is induced, and the morphology and distribution of dislocations and twins are adjusted, thereby improving the hardness and wear resistance at low temperatures of the repaired bearing.

[0030] Furthermore, the annealing temperature of the multi-pass medium-temperature annealing is 550-750℃, the number of annealing passes is 4-10, and the total annealing time is 15-60 min.

[0031] Furthermore, the second cryogenic cooling is cooling in a liquid nitrogen tank or a dry ice tank.

[0032] In this invention, the second cryogenic cooling is rapid cooling to liquid nitrogen temperature or dry ice temperature.

[0033] This invention optimizes the microstructure of the material and improves its overall mechanical properties by combining multi-pass medium-temperature annealing with a second low-temperature cooling.

[0034] Furthermore, the cryogenic treatment is carried out in liquid nitrogen for 2-50 hours.

[0035] It should be noted that the cryogenic treatment is carried out in liquid nitrogen, specifically after a second cryogenic cooling process, it is carried out separately in a liquid nitrogen bath.

[0036] Optionally, the cryogenic treatment can be a single cryogenic treatment lasting 2-50 hours, or a treatment cycle of 2 hours, repeated 1-25 times.

[0037] This invention stabilizes the microstructure of high-entropy alloys through cryogenic treatment, reduces bearing dimensional changes caused by long-term service at low temperatures, and improves the operational stability of bearing bushes.

[0038] Furthermore, the roughing process involves turning the arc-additive processing area.

[0039] In this process, it is machined to make it slightly larger than the finished product size (approximately 0.3-0.5 mm larger than the finished product size).

[0040] After rough machining, X-ray or ultrasonic testing is performed on the arc additive manufacturing area. If defects such as holes or cracks still exist in the repaired area, the pretreatment, arc additive manufacturing, high-temperature short-time annealing, first low-temperature cooling, multi-pass medium-temperature annealing, second low-temperature cooling, and cryogenic treatment are repeated until there are no defects in the repaired area.

[0041] Furthermore, the finishing process involves grinding, milling, and polishing the areas treated with electric arc additive manufacturing.

[0042] Optionally, the milling process is to process equally spaced spiral grooves through milling, with the following process parameters: rotation speed of 1300r / min-1500r / min, feed rate of 300-350mm / min, grooves being semi-circular or square, diameter or depth of 0.2-0.4mm±0.05mm, helix angle of 30°-60°, and groove spacing of 15-30mm.

[0043] Grinding is used to bring the finished product to within the allowable size range; milling is used to give the finished product high machining accuracy; and polishing is used to make the surface finish of the bearing meet the requirements.

[0044] Fourth technical solution of the present invention: A method for preparing a bearing bush for a sliding bearing of an LNG cryogenic submersible pump, comprising the following steps:

[0045] Prepare high-entropy alloy raw materials according to the general formula of the above high-entropy alloys, for later use;

[0046] The high-entropy alloy raw material was prepared into a bearing precursor by arc additive manufacturing.

[0047] The bearing shell of the LNG cryogenic submersible pump sliding bearing is obtained by sequentially undergoing high-temperature short-time annealing, first cryogenic cooling, multi-pass medium-temperature annealing, second cryogenic cooling, deep cryogenic treatment, rough machining, and fine machining.

[0048] Furthermore, the high-entropy alloy raw material includes elemental powders and / or intermediate alloy powders.

[0049] The high-entropy alloy raw materials include a variety of Mn powder, Fe powder, Cr powder, Ni powder, Cu powder, Al powder, Ca powder, Si powder, Ti powder, Al-Ce powder, Al-La powder, Al-Y powder, aluminum-manganese alloy powder, aluminum-iron alloy powder, aluminum-chromium alloy powder, aluminum-nickel alloy powder, aluminum-copper alloy powder, aluminum-calcium alloy powder, aluminum-silicon alloy powder, and aluminum-titanium alloy powder, to support the general formula of the above-mentioned high-entropy alloy.

[0050] Furthermore, the process parameters for the electric arc additive manufacturing are as follows: pulse energy of 0.5-2.5J, pulse frequency of 5-25Hz, operating current of 40-65A, and feed speed of 150-500mm / min; the protective gas is Ar, and the flow rate is 10-20L / min.

[0051] Optionally, in the arc additive manufacturing process, adjacent cladding materials are rotated by 15°-45°.

[0052] Stress concentration can be avoided by rotating the device 15°–45°.

[0053] Furthermore, the high-temperature short-time annealing is performed using high-frequency induction heating.

[0054] Optionally, the process parameters for the high-frequency induction heating are: power of 10-16KW, heating rate of 15-50℃ / s, heating temperature of 950-1100℃, induction heating time of 10-60s, and frequency range of 200-250KHz.

[0055] Furthermore, the first cryogenic cooling is performed in a liquid nitrogen bath or a dry ice bath.

[0056] This invention enhances lattice distortion energy and increases the driving force for phase transition during multi-pass intermediate-temperature annealing by rapidly cooling at low temperatures (first low-temperature cooling).

[0057] Furthermore, the multi-pass intermediate-temperature annealing is carried out in a vacuum resistance furnace or a gas-protected resistance furnace.

[0058] By reducing the high internal stress of the bearing precursor through multi-pass medium-temperature annealing, nano-precipitates are induced to form, and the morphology and distribution of dislocations and twins are adjusted, thereby improving the hardness and wear resistance of the bearing at low temperatures.

[0059] Furthermore, the annealing temperature of the multi-pass medium-temperature annealing is 550-750℃, the number of annealing passes is 4-10, and the total annealing time is 15-60 min.

[0060] Furthermore, the second cryogenic cooling is cooling in a liquid nitrogen tank or a dry ice tank.

[0061] This invention optimizes the microstructure of materials and improves their performance by combining multi-pass medium-temperature annealing with a second low-temperature cooling.

[0062] Furthermore, the cryogenic treatment is carried out in liquid nitrogen for 2-50 hours.

[0063] Optionally, the cryogenic treatment can be a single cryogenic treatment lasting 2-50 hours, or a treatment cycle of 2 hours, repeated 1-25 times.

[0064] It should be noted that the cryogenic treatment is carried out in liquid nitrogen, specifically after a second cryogenic cooling process, it is carried out separately in a liquid nitrogen bath.

[0065] Furthermore, the rough machining is to perform turning machining on the bearing bush precursor.

[0066] In this process, it is machined to make it slightly larger than the finished product size (approximately 0.3-0.5 mm larger than the finished product size).

[0067] Furthermore, the finishing process involves grinding, milling, and polishing the arc additive manufacturing area.

[0068] Optionally, the milling process is to process equally spaced spiral grooves through milling, with the following process parameters: rotation speed of 1300r / min-1500r / min, feed rate of 300-350mm / min, grooves being semi-circular or square, diameter or depth of 0.2-0.4mm±0.05mm, helix angle of 30°-60°, and groove spacing of 15-30mm.

[0069] The sliding bearings repaired, remanufactured, or prepared by this invention can be used in LNG cryogenic submersible pumps and other equipment operating in cryogenic environments.

[0070] The present invention discloses the following technical effects:

[0071] This invention can effectively improve the stability and service life of LNG cryogenic submersible pump bearings, which helps to reduce maintenance time and operating costs.

[0072] The electric arc additive remanufacturing repair process of this invention is simple, and the repaired and remanufactured sliding bearing has high hardness and strong low-temperature wear resistance.

[0073] This invention repairs sliding bearings through arc additive manufacturing, which not only improves the strength and low-temperature characteristics of the sliding bearing bush, but also provides high resistance to corrosion, wear, and fatigue. It can be used in environments lubricated by liquid oxygen, liquid nitrogen, liquefied natural gas, etc., and exhibits excellent performance in terms of reliability and lifespan.

[0074] This invention uses cryogenic treatment to stabilize the dimensional accuracy of the bearing bush, thereby improving the reliability and safety of the sliding bearing during service.

[0075] This invention enables the one-time molding of sliding bearings for LNG cryogenic submersible pumps, eliminating the need for conventional equipment such as induction melting furnaces and forging presses, thus reducing the production cost of sliding bearings. Attached Figure Description

[0076] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0077] Figure 1 This is a diagram of the bearing assembly.

[0078] Figure 2 This is a split view of the bearing.

[0079] Figure 3 For bearing bushes. Detailed Implementation

[0080] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0081] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0082] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0083] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0084] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0085] The raw materials used in the high-entropy alloy of this invention are all commercially available products with a purity of not less than 99.9%.

[0086] In the specific embodiments of the present invention, the room temperature and ambient temperature are both 20-30℃.

[0087] The specifications of the bearing substrate of the LNG cryogenic submersible pump sliding bearing to be repaired in this invention are as follows: inner diameter 36mm, length 26mm, and thickness 4.5mm.

[0088] Figure 1 This is a diagram of the bearing assembly. Figure 2 This is a split view of the bearing. Figure 3 For bearing bushes.

[0089] Example 1

[0090] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0091] S1, According to the general formula (CrFeMnNi) 0.65 Cu 0.2 Al 0.12 Si 0.03 Prepare the raw materials, which include: Mn powder, Fe powder, Cr powder, Ni powder, Cu powder, Si powder, and Al powder;

[0092] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0093] S3. Perform arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an arc additive manufactured component. The parameters of the arc additive manufacturing are: pulse energy 0.8J; pulse frequency 10Hz; working current 45A; feed speed 150mm / min; protective gas Ar, protective gas flow rate 12L / min.

[0094] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0095] The parameters for high-frequency induction heating are: power 10KW, heating rate 46℃ / s, heating temperature 920℃, induction heating time 20s, and frequency 220KHz.

[0096] S5. After the first low-temperature cooling, the furnace is subjected to multiple passes of medium-temperature annealing in a gas-protected resistance furnace. After the multiple passes of medium-temperature annealing are completed, the furnace is directly subjected to rapid cooling in a liquid nitrogen bath for the second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0097] The temperature of the multi-pass medium-temperature annealing treatment is 550℃, the number of annealing passes is 4, and the treatment time for each pass is 5 minutes.

[0098] S6. After the second cryogenic cooling is completed, the sample is subjected to deep cryogenic treatment in a liquid nitrogen bath for 15 hours.

[0099] S7. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size); the machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area; if obvious defects are found, the aforementioned grinding, cleaning and arc additive remanufacturing S2-S7 processes can be repeated until there are no defects in the remanufactured area;

[0100] S8. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0101] Example 2

[0102] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0103] S1, According to the general formula (CrFeMnNi) 0.6 Cu 0.21 Al 0.15 Ti 0.04 Prepare the raw materials, which include: Ti powder, Cr powder, Fe powder, Mn powder, Ni powder, Cu powder, Al powder, AlFe alloy powder, AlCr alloy powder, and AlTi alloy powder;

[0104] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0105] S3. Perform electric arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an electric arc additive manufactured component. The parameters of the electric arc additive manufacturing are: pulse energy 2J; pulse frequency 10Hz; working current 55A; feed speed 300mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0106] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0107] The parameters for high-frequency induction heating are: power 12KW, heating rate 30℃ / s, heating temperature 960℃, induction heating time 32s, and frequency 225KHz.

[0108] S5. After the first low-temperature cooling, the furnace is subjected to multiple passes of medium-temperature annealing in a gas-protected resistance furnace. After the multiple passes of medium-temperature annealing are completed, the furnace is directly subjected to rapid cooling in a liquid nitrogen bath for the second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0109] The temperature of the multi-pass medium-temperature annealing treatment is 550℃, the number of annealing passes is 5, and the treatment time for each pass is 5 minutes.

[0110] S6. After the second cryogenic cooling is completed, the sample is subjected to deep cryogenic treatment in a liquid nitrogen bath for 10 hours.

[0111] S7. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size); the machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area; if obvious defects are found, the aforementioned grinding, cleaning and arc additive remanufacturing S2-S7 processes can be repeated until there are no defects in the remanufactured area;

[0112] S8. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0113] Example 3

[0114] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0115] S1, According to the general formula (CrFeMnNi) 0.7 Cu 0.16 Al 0.125 Ti 0.015 Prepare the raw materials, which include: FeCr powder, FeMn powder, FeNi powder, CuCr powder, AlTi alloy powder, AlFe alloy powder, AlMn alloy powder, and AlNi alloy powder;

[0116] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0117] S3. Perform electric arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an electric arc additive manufactured component. The parameters of the electric arc additive manufacturing are: pulse energy 2J; pulse frequency 15Hz; working current 55A; feed speed 300mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0118] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0119] The parameters for high-frequency induction heating are: power 14KW, heating rate 20℃ / s, heating temperature 1000℃, induction heating time 50s, and frequency 230KHz.

[0120] S5. After the first low-temperature cooling, the furnace is subjected to multiple passes of medium-temperature annealing in a gas-protected resistance furnace. After the multiple passes of medium-temperature annealing are completed, the furnace is directly subjected to rapid cooling in a liquid nitrogen bath for the second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0121] The temperature of the multi-pass medium-temperature annealing treatment is 650℃, the number of annealing passes is 5, and the treatment time for each pass is 4 minutes.

[0122] S6. After the second cryogenic cooling is completed, the cryogenic treatment is carried out in a liquid nitrogen bath for 20 hours. The cryogenic treatment is carried out in 2-hour cycles, and a total of 10 cycles are carried out.

[0123] S7. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size); the machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area; if obvious defects are found, the aforementioned grinding, cleaning and arc additive remanufacturing S2-S7 processes can be repeated until there are no defects in the remanufactured area;

[0124] S8. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0125] Example 4

[0126] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0127] S1, According to the general formula (CrFeMnNi) 0.67 Cu 0.17 Al 0.12 Ca 0.04 Prepare the raw materials, which include: Cr powder, Fe powder, Mn powder, Ni powder, Cu powder, AlCr alloy powder, AlFe alloy powder, and AlCa alloy powder;

[0128] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0129] S3. Perform arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an arc additive manufactured component. The parameters of the arc additive manufacturing are: pulse energy 2.2J; pulse frequency 15Hz; working current 60A; feed speed 350mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0130] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0131] The parameters for high-frequency induction heating are: power 16KW, heating rate 26℃ / s, heating temperature 1040℃, induction heating time 40s, and frequency 220KHz.

[0132] S5. After the first low-temperature cooling, the furnace is subjected to medium-temperature annealing in a gas-protected resistance furnace. After the medium-temperature annealing is completed, the furnace is directly subjected to rapid cooling in a liquid nitrogen bath for the second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0133] The temperature of the multi-pass medium-temperature annealing treatment is 600℃, the number of annealing passes is 5, and the treatment time for each pass is 4 minutes.

[0134] S6. After the second cryogenic cooling is completed, the cryogenic treatment is carried out in a liquid nitrogen bath for 32 hours. The cryogenic treatment is carried out in 2-hour cycles, and a total of 16 cycles are carried out.

[0135] S7. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size); the machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area; if obvious defects are found, the aforementioned grinding, cleaning and arc additive remanufacturing S2-S7 processes can be repeated until there are no defects in the remanufactured area;

[0136] S8. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0137] Example 5

[0138] The manufacturing steps for the bearing bush of the sliding bearing for the LNG cryogenic submersible pump include:

[0139] S1, According to the general formula (CrFeMnNi) 0.7 Cu 0.15 Al 0.12 Si 0.03 Prepare the raw materials, which include: Mn powder, Fe powder, Cr powder, Ni powder, Cu powder, Al powder, Si powder, and AlFe alloy powder, AlCr alloy powder, AlCu alloy powder, AlSi alloy powder, and AlTi alloy powder.

[0140] S2. Using 9Cr18 steel as the substrate and the above-mentioned powder as the raw material, the bearing bush for the sliding bearing of the LNG cryogenic submersible pump is prepared by electric arc additive manufacturing technology. The parameters of the electric arc additive manufacturing process are: pulse energy 0.8J; pulse frequency 10Hz; working current 45A; feed speed 150mm / min; protective gas Ar, protective gas flow rate 12L / min.

[0141] S3. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0142] The parameters for high-frequency induction heating are: power 10KW, heating rate 46℃ / s, heating temperature 920℃, induction heating time 20s, and frequency 220KHz.

[0143] S4. After the first low-temperature cooling, the furnace is subjected to multiple-pass medium-temperature annealing in a gas-protected resistance furnace. After the multiple-pass medium-temperature annealing is completed, the furnace is directly subjected to rapid cooling in a liquid nitrogen bath for the second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0144] The temperature of the multi-pass medium-temperature annealing treatment is 550℃, the number of annealing passes is 4, and the treatment time for each pass is 5 minutes.

[0145] S5. After the second cryogenic cooling is completed, the product is subjected to deep cryogenic treatment in a liquid nitrogen bath for 15 hours.

[0146] S6. After cryogenic treatment, the arc additive manufacturing area is turned to make it slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size). Then, the part is ground to bring it within the allowable range of the finished product size (inner diameter 35 mm, length 25 mm, thickness 4 mm). Subsequently, equally spaced helical grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a rotation speed of 1400 r / min and a feed rate of 320 mm / min. The grooves are semi-circular with a radius of 0.25 mm, a helix angle of 35°, and a groove spacing of 15 mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6 μm.

[0147] Comparative Example 1

[0148] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0149] S1, According to the general formula (CrFeMnNi) 0.65 Cu 0.2 Al 0.12 Si 0.03 Prepare the raw materials, which are: Mn powder, Fe powder, Cr powder, Ni powder, Cu powder, Si powder and Al powder;

[0150] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface to obtain pre-treated bearing components.

[0151] S3. Perform arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an arc additive manufactured component. The parameters of the arc additive manufacturing are: pulse energy 0.8J; pulse frequency 10Hz; working current 45A; feed speed 150mm / min; protective gas Ar, protective gas flow rate 12L / min.

[0152] S4. Arc additive manufacturing components are not subjected to high-temperature short-time annealing. Instead, they are directly subjected to medium-temperature annealing in a gas-protected resistance furnace. After the medium-temperature annealing is completed, they are directly subjected to rapid cooling in a liquid nitrogen bath for a second low-temperature cooling, cooling to the liquid nitrogen temperature.

[0153] The temperature of the multi-pass medium-temperature annealing treatment is 550℃, the number of annealing passes is 4, and the treatment time for each pass is 5 minutes.

[0154] S5. After the second cryogenic cooling is completed, the product is subjected to deep cryogenic treatment in a liquid nitrogen bath for 15 hours.

[0155] S6. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size). The machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area. If obvious defects are found, the aforementioned grinding, cleaning, and arc additive remanufacturing S2-S6 processes can be repeated until there are no defects in the remanufactured area.

[0156] S7. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0157] Comparative Example 2

[0158] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0159] S1, According to the general formula (CrFeMnNi) 0.6 Cu 0.16 Al 0.2 Ti 0.04 Prepare the raw materials, which include: Ti powder, Cr powder, Fe powder, Mn powder, Ni powder, Cu powder, Al powder, AlFe alloy powder, AlCr alloy powder, and AlTi alloy powder;

[0160] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0161] S3. Perform electric arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an electric arc additive manufactured component. The parameters of the electric arc additive manufacturing are: pulse energy 2J; pulse frequency 10Hz; working current 55A; feed speed 300mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0162] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating. After the high-temperature short-time annealing is completed, it is directly subjected to the first low-temperature cooling in a liquid nitrogen bath to cool to the liquid nitrogen temperature.

[0163] The parameters for high-frequency induction heating are: power 12KW, heating rate 30℃ / s, heating temperature 960℃, induction heating time 32s, and frequency 225KHz.

[0164] S5. After the first low-temperature cooling, a single-pass long-term medium-temperature annealing treatment is carried out in a gas-protected resistance furnace, wherein the annealing temperature is 550℃ and the annealing time is 25min.

[0165] S6. After the second cryogenic cooling is completed, the sample is subjected to deep cryogenic treatment in a liquid nitrogen bath for 10 hours.

[0166] S7. After the cryogenic treatment, the arc additive manufacturing area is machined to make it slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size);

[0167] S8. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0168] Comparative Example 3

[0169] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0170] S1, According to the general formula (CrFeMnNi) 0.7 Cu 0.16 Al 0.125 Ti 0.015 Prepare the raw materials, which are: Ti powder, Cr powder, Fe powder, Mn powder, Ni powder, Cu powder and Al powder;

[0171] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0172] S3. Perform electric arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an electric arc additive manufactured component. The parameters of the electric arc additive manufacturing are: pulse energy 2J; pulse frequency 15Hz; working current 55A; feed speed 300mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0173] S4. The arc additive manufacturing parts are subjected to multi-pass medium-temperature annealing in a gas-protected resistance furnace. After the multi-pass medium-temperature annealing is completed, they are directly cooled in a liquid nitrogen bath for a second low-temperature cooling until they reach the liquid nitrogen temperature.

[0174] The temperature of the multi-pass medium-temperature annealing treatment is 650℃, the number of annealing passes is 5, and the treatment time for each pass is 4 minutes.

[0175] S5. After the second cryogenic cooling is completed, the cryogenic treatment is carried out in a liquid nitrogen bath for 20 hours. The cryogenic treatment is carried out in 2-hour cycles, and a total of 10 cycles are carried out.

[0176] S6. After the cryogenic treatment, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size). The machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area. If obvious defects are found, the aforementioned grinding, cleaning, and arc additive remanufacturing S2-S6 processes can be repeated until there are no defects in the remanufactured area.

[0177] S7. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0178] Comparative Example 4

[0179] A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, comprising the following steps:

[0180] S1, According to the general formula (CrFeMnNi) 0.67 Cu 0.17 Al 0.12 Ca 0.04 Prepare the raw materials, which include: Cr powder, Fe powder, Mn powder, Ni powder, Cu powder, AlCr alloy powder, AlFe alloy powder, and AlCa alloy powder;

[0181] S2. Grind the bearing substrate of the sliding bearing of the LNG cryogenic submersible pump to be repaired, and remove wear, burning, cracks, deformation, flaking, peeling, corrosion pits, etc. on the bearing surface. Then remove the dust, impurities and dirt on the surface, clean it with high-concentration ethanol, and then preheat the bearing substrate to 160°C to obtain the pretreated bearing component.

[0182] S3. Perform arc additive manufacturing on the pre-treated bearing component to be repaired to obtain an arc additive manufactured component. The parameters of the arc additive manufacturing are: pulse energy 2.2J; pulse frequency 15Hz; working current 60A; feed speed 350mm / min; protective gas Ar, protective gas flow rate 16L / min.

[0183] S4. The arc additive manufacturing component is subjected to high-temperature short-time annealing by high-frequency induction heating, and then water-cooled after the high-temperature short-time annealing is completed.

[0184] The parameters for high-frequency induction heating are: power 16KW, heating rate 26℃ / s, heating temperature 1040℃, induction heating time 40s, and frequency 220KHz.

[0185] S5. The sample is annealed at medium temperature in a gas-protected resistance furnace, and then air-cooled directly after the medium-temperature annealing is completed.

[0186] The temperature for the medium-temperature annealing treatment was 600℃, and the time was 20 minutes.

[0187] S6. After the medium-temperature annealing, the arc additive manufacturing area is machined to be slightly larger than the finished product size (approximately 0.3 mm larger than the finished product size). The machined cladding area is subjected to X-ray or ultrasonic testing to check for defects such as holes and cracks in the repaired area. If obvious defects are found, the aforementioned grinding, cleaning, and arc additive remanufacturing S2-S6 processes can be repeated until there are no defects in the remanufactured area.

[0188] S7. After turning, grinding is performed to bring the finished product to the allowable size range (inner diameter 35mm, length 25mm, thickness 4mm). Then, equally spaced spiral grooves are milled on the ground surface using a CNC milling machine. Alloy steel milling cutters are used, with a speed of 1400r / min, a feed rate of 320mm / min, and the grooves are semi-circular with a radius of 0.25mm, a helix angle of 35°, and a groove spacing of 15mm. Finally, fine grinding is performed to make the surface roughness of the bearing reach Ra≤1.6μm.

[0189] Comparative Example 5

[0190] Compared with Example 5, the selected raw material ratio, electric arc additive processing parameters, heat treatment parameters and cryogenic treatment parameters are the same. The difference is that this process adds X-ray flaw detection, grinding of the part to be repaired, inspection of the repair area, repeated grinding and repair process, which is suitable for the repair and remanufacturing of sliding bearings of LNG cryogenic submersible pumps.

[0191] Comparative Examples 6-13

[0192] The only difference from Example 1 is the element ratio, as shown in Table 1.

[0193] Table 1

[0194] Comparative Example 6 <![CDATA[(CrFeMnNi) 0.82 With 0.03 the 0.12 And 0.03 ]]> The proportion of (CrFeMnNi) is higher than 0.8%. Comparative Example 7 <![CDATA[(CrFeMnNi) 0.5 With 0.25 the 0.135 And 0.115 ]]> The proportion of (CrFeMnNi) is less than 0.55%. Comparative Example 8 <![CDATA[(CrFeMnNi) 0.55 With 0.32 the 0.115 And 0.015 ]]> The proportion of Cu is higher than 0.3%. Comparative Example 9 <![CDATA[(CrFeMnNi) 0.7 With 0.14 the 0.145 And 0.015 ]]> The proportion of Cu is less than 0.15%. Comparative Example 10 <![CDATA[(CrFeMnNi) 0.675 With 0.15 the 0.16 And 0.015 ]]> The proportion of Al is higher than 0.15 Comparative Example 11 <![CDATA[(CrFeMnNi) 0.7 With 0.25 the 0.035 And 0.015 ]]> The proportion of Al is less than 0.1 Comparative Example 12 <![CDATA[(CrFeMnNi) 0.6 With 0.165 the 0.135 And 0.1 ]]> The proportion of Si is higher than 0.05%. Comparative Example 13 <![CDATA[(CrFeMnNi) 0.6 With 0.25 the 0.147 And 0.003 ]]> The proportion of Si is less than 0.005

[0195] Test case

[0196] The performance parameters of the bearings prepared in Examples 1-5 and Comparative Examples 1-13 were tested, and the results are shown in Table 2.

[0197] The method for testing microhardness is to press a diamond indenter of a microhardness tester into the material surface under a certain test force (6N), and measure the diagonal length of the indentation to calculate the hardness value.

[0198] The average coefficient of friction is tested by using a reciprocating friction tester to simulate the reciprocating motion in actual use and to measure the change of friction force with time and number of cycles.

[0199] Table 2

[0200] Example 1 536.1 0.23 Example 2 495.8 0.21 Example 3 498.2 0.29 Example 4 525.7 0.26 Example 5 512.3 0.26 Comparative Example 1 486.5 0.32 Comparative Example 2 478.2 0.39 Comparative Example 3 502.3 0.33 Comparative Example 4 482.4 0.48 Comparative Example 5 498.6 0.39 Comparative Example 6 513.5 0.36 Comparative Example 7 496.6 0.28 Comparative Example 8 522.5 0.33 Comparative Example 9 477.4 0.26 Comparative Example 10 466.3 0.25 Comparative Example 11 485.6 0.34 Comparative Example 12 478.3 0.26 Comparative Example 13 488.9 0.30

[0201] As can be seen from the data in Table 2 of the embodiments and comparative examples, the repair method provided by the present invention, which includes pretreatment of the bearing substrate, arc additive manufacturing, high-temperature short-time annealing, first low-temperature cooling, multi-pass medium-temperature annealing, second low-temperature cooling, cryogenic treatment, rough machining, and fine machining, achieves the goal of good bonding between the cladding layer and the substrate. By performing high-temperature short-time annealing after arc additive manufacturing, the surface structure of the high-entropy alloy cladding layer is refined. Cryogenic treatment is used to control the morphology and distribution of defects such as dislocations and stacking faults in the cladding layer, enhancing the hardness and wear resistance of the repaired bearing. Under the combined effect of the above processes, the goal of arc additive remanufacturing of sliding bearings is achieved, improving the service life of the bearing. Furthermore, the microhardness of the sliding bearing is ≥595.8HV, and the average coefficient of friction is ≤0.29, meeting the requirements of high strength and high wear resistance, which is beneficial for applications in low-temperature environments.

[0202] As can be seen from the data in Example 5, the bearing substrate prepared by the method of the present invention has good wear resistance at low temperatures.

[0203] A comparison of the data from Comparative Example 5 and Example 1 shows that when other high-entropy alloy powders are used to repair the bearing, the bearing hardness decreases and the coefficient of friction increases.

[0204] A comparison of the data from Comparative Examples 6-13 and Example 1 shows that changing the element ratio alters the hardness and coefficient of friction of the bearing. Specifically, changes in the value of x in the general formula result in changes in the bearing's hardness and compressive yield strength; changes in the value of y result in changes in the bearing's yield strength and hardness, altering the bearing alloy's plasticity; changes in the value of z result in changes in the bearing's hardness and tensile strength; and changes in the value of w result in changes in the bearing's hardness, strength, wear resistance, and corrosion resistance.

[0205] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0206] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for arc additive remanufacturing repair of sliding bearings in LNG cryogenic submersible pumps, characterized in that the steps include... include: The bearing substrate of the sliding bearing of the LNG cryogenic submersible pump is pretreated to obtain a pretreated component; Prepare high-entropy alloy raw materials according to the general formula of high-entropy alloys, for later use; The general formula for the high-entropy alloy is: (CrFeMnNi) x Cu y Al z Z w Where Z is selected from Si, Ti or Ca; x is 0.550-0.800, y is 0.150-0.300, z is 0.100-0.150, w is 0.005-0.05, and the sum of x, y, z and w is 1; The high-entropy alloy raw material is processed by arc additive manufacturing to obtain an arc-added processed component. The arc additive manufacturing process involves sequentially undergoing high-temperature short-time annealing, first low-temperature cooling, multi-pass medium-temperature annealing, second low-temperature cooling, cryogenic treatment, rough machining, and fine machining to obtain the repaired bearing component.

2. The method as described in claim 1, characterized in that, The pretreatment steps include: the bearing substrate is sequentially ground, cleaned, and preheated to obtain a pretreated part; the high-entropy alloy raw material includes elemental powder and / or intermediate alloy powder; the process parameters of the arc additive manufacturing are: pulse energy of 0.5-2.5J, pulse frequency of 5-25Hz, working current of 40-65A, and feed speed of 150-500mm / min; the protective gas is Ar, and the flow rate is 10-20L / min; the adjacent cladding materials in the arc additive manufacturing process rotate... The temperature range is 15°-45°C; the high-temperature short-time annealing is performed by high-frequency induction heating; the first low-temperature cooling is performed in a liquid nitrogen bath or a dry ice bath; the multi-pass medium-temperature annealing is performed in a vacuum resistance furnace or a gas-protected resistance furnace; the annealing temperature of the multi-pass medium-temperature annealing is 550-750°C, the number of annealing passes is 4-10, and the total annealing time is 15-60 min; the second low-temperature cooling is performed in a liquid nitrogen bath or a dry ice bath; the cryogenic treatment is performed in liquid nitrogen for 2-50 h.

3. The method as described in claim 2, characterized in that, The cleaning is performed using acetone or ethanol; the preheating temperature is 100-200℃; the process parameters for the high-frequency induction heating are: power 10-16KW, heating rate 15-50℃ / s, heating temperature 950-1100℃, induction heating time 10-60s, and frequency range 200-250 KHz; the cryogenic treatment is a one-time cryogenic treatment for 2-50 hours, or a treatment cycle of 2 hours, repeated 1-25 times.

4. The method as described in claim 1, characterized in that, The roughing process involves turning the arc-additive treated area; it also includes X-ray or ultrasonic testing of the arc-additive treated area after roughing. If holes or cracks still exist in the repaired area, the process is repeated with pretreatment, arc-addition, high-temperature short-time annealing, first low-temperature cooling, multi-pass medium-temperature annealing, second low-temperature cooling, and cryogenic treatment until the repaired area is free of defects. The finishing process involves grinding, milling, and polishing the arc-additive treated area.

5. The method as described in claim 4, characterized in that, The milling process involves machining equally spaced spiral grooves using milling. The process parameters are: rotation speed of 1300r / min-1500r / min, feed rate of 300-350mm / min, grooves that are semi-circular or square, diameter or depth of 0.2-0.4mm, spiral helix angle of 30°-60°, and groove spacing of 15-30mm.

6. A method for manufacturing a bearing bush for a sliding bearing of an LNG cryogenic submersible pump, characterized in that the step... include: Prepare high-entropy alloy raw materials according to the general formula of high-entropy alloys, for later use; The general formula for the high-entropy alloy is: (CrFeMnNi) x Cu y Al z Z w Where Z is selected from Si, Ti or Ca; x is 0.550-0.800, y is 0.150-0.300, z is 0.100-0.150, w is 0.005-0.05, and the sum of x, y, z and w is 1; The high-entropy alloy raw material was prepared into a bearing precursor by arc additive manufacturing. The bearing shell precursor for the LNG cryogenic submersible pump sliding bearing is obtained by sequentially undergoing high-temperature short-time annealing, first cryogenic cooling, multi-pass medium-temperature annealing, second cryogenic cooling, deep cryogenic treatment, rough machining, and fine machining.

7. The preparation method according to claim 6, characterized in that, The high-entropy alloy raw material includes elemental powder and / or intermediate alloy powder; the process parameters of the arc additive manufacturing are: pulse energy of 0.5-2.5J, pulse frequency of 5-25Hz, working current of 40-65A, and feed speed of 150-500mm / min; the protective gas is Ar, with a flow rate of 10-20L / min; the adjacent cladding materials in the arc additive manufacturing process are rotated by 15°-45°; the high-temperature short-time annealing is performed by high-frequency induction heating; the first low-temperature cooling is carried out in a liquid nitrogen bath or dry... Cooling is performed in an ice bath; the multi-pass medium-temperature annealing is carried out in a vacuum resistance furnace or a gas-protected resistance furnace; the annealing temperature of the multi-pass medium-temperature annealing is 550-750℃, the number of annealing passes is 4-10, and the total annealing time is 15-60 min; the second low-temperature cooling is performed in a liquid nitrogen bath or a dry ice bath; the cryogenic treatment is carried out in liquid nitrogen for 2-50 h; the rough machining is turning the bearing precursor; the finish machining is grinding, milling, and polishing the bearing precursor.

8. The preparation method according to claim 7, characterized in that, The process parameters for the high-frequency induction heating are: power of 10-16KW, heating rate of 15-50℃ / s, heating temperature of 950-1100℃, induction heating time of 10-60s, and frequency range of 200-250 KHz; the cryogenic treatment is a one-time cryogenic treatment for 2-50 hours, or a treatment cycle of 2 hours, and 1-25 treatments; the milling process is to process equally spaced spiral grooves through milling, with the following process parameters: rotation speed of 1300r / min-1500r / min, feed rate of 300-350mm / min, grooves are semi-circular or square, diameter or depth of 0.2-0.4mm±0.05mm, spiral helix angle of 30°-60°, and groove spacing of 15-30mm.

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