Laser cladding powder and laser cladding method for seawater circulating pump impeller

Abstract

The invention discloses laser cladding powder and a laser cladding method for a seawater circulating pump impeller. The invention relates to laser cladding powder, which is nickel-based alloy powder, is used for repairing an impeller, and comprises less than or equal to 0.1 wt% of C, less than or equal to 0.5 wt% of Si, 20.0-23.0 wt% of Cr, less than or equal to 5.0 wt% of Fe, 8.0-10.0 wt% of Mo, 3.15-4.15 wt% of Nb and the balance of Ni. And the particle size of the laser cladding powder is 53-150 microns. The laser cladding method for the impeller of the seawater circulating pump adopts a laser cladding method, and the laser cladding powder is used as a cladding material to repair the impeller. A duplex stainless steel cladding layer and a nickel-based alloy functional cladding layer are sequentially formed on a base body of the impeller by adopting a laser cladding method. The laser cladding powder is used for repairing the impeller of the seawater circulating pump, and the use function can be well improved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cladding, and more particularly, to a laser cladding powder and a method for laser cladding of a seawater circulation pump impeller. Background Art

[0002] During the service process of the seawater circulation pump impeller, it is subjected to long-term erosion by seawater, and its surface undergoes wear and corrosion failure, showing fish-scale patterns and plow-shaped grooves, and even through-failure, making it difficult to meet the use requirements. In addition, the cost of impeller replacement is high and the replacement cycle is long. To reduce the economic losses of nuclear power plant shutdown operation, it is urgent to repair its damaged surface and improve the service life of the impeller.

[0003] Laser cladding is an additive remanufacturing technology that can achieve damage repair and surface modification. Compared with traditional fusion welding methods, laser cladding repair technology has lower heat input, smaller heat-affected zone formed during repair, lower residual stress, smaller matrix deformation, and high automation of laser cladding technology, which can achieve high-precision repair of complex surfaces and reduce subsequent processing volume. In addition, compared with thermal spraying and high-velocity oxy-fuel spraying technologies, the laser cladding repair layer and the matrix are metallurgically bonded, greatly reducing the risk of the repair layer falling off after service and helping to improve the quality of nuclear power operation and maintenance.

[0004] The research on the detection of fault characteristic gases has important practical significance for ensuring the safe and reliable operation of power systems. The present invention is proposed under this circumstance. Summary of the Invention

[0005] The purpose of the present invention is to provide a laser cladding powder and a method for laser cladding of a seawater circulation pump impeller, aiming to achieve high-quality repair of the seawater circulation pump impeller of a nuclear power plant.

[0006] The present invention provides a laser cladding powder, which is a nickel-based alloy powder for impeller repair, and includes: C ≤ 0.1 wt%, Si ≤ 0.5 wt%, Cr 20.0 - 23.0 wt%, Fe ≤ 5.0 wt%, Mo 8.0 - 10.0 wt%, Nb 3.15 - 4.15 wt%, and the balance is Ni.

[0007] Optionally, the particle size of the laser cladding powder is 53 - 150 μm.

[0008] A method for laser cladding of a seawater circulation pump impeller uses the laser cladding method with the above laser cladding powder as the cladding material to repair the impeller.

[0009] Optionally, by using the method of laser cladding, a duplex stainless steel cladding layer and a nickel-based alloy functional cladding layer are sequentially formed on the substrate of the impeller. The duplex stainless steel cladding layer uses duplex stainless steel powder as the cladding material, and the nickel-based alloy functional cladding layer uses the laser cladding powder as the cladding material. The duplex stainless steel powder and the laser cladding powder need to be dried before cladding.

[0010] Optionally, the duplex stainless steel powder and the substrate are made of the same material. The duplex stainless steel powder includes: C≤0.03wt%, Si≤1wt%, Mn≤2wt%, P≤0.025wt%, S≤0.025wt%, Cr 24.5~26.5wt%, Ni 5.5~7wt%, Mo 2.5~3.5wt%, N 0.12~0.25wt%, O≤0.03wt%, and the balance is Fe.

[0011] Optionally, two layers of the duplex stainless steel cladding layer and one layer of the nickel-based alloy functional cladding layer are sequentially formed on the substrate of the impeller.

[0012] Optionally, after each layer of cladding, the workpiece is cooled to the interlayer temperature, and then the next layer of cladding is carried out. The interlayer temperature is 100~120°C.

[0013] Optionally, the defect positions of the impeller are divided for repair positions. After positioning, a cladding program is compiled, and a jump repair sequence is adopted. First, single-sided cladding is carried out at the defect positions, and then the other side is cladded in the same way. A machining allowance of 0.5~1.0mm is reserved on both sides.

[0014] Optionally, the laser power for forming the duplex stainless steel cladding layer is 1600W, the scanning speed is 10mm / s, the powder feeding rate is 1r / min, the overlapping rate is 50%, the powder feeding gas flow rate is 7.5L / min, and the shielding gas flow rate is 25L / min.

[0015] Optionally, the laser power for forming the nickel-based alloy functional cladding layer is 1400W, the scanning speed is 10mm / s, the powder feeding rate is 0.5r / min, the overlapping rate is 50%, the powder feeding gas flow rate is 5.5L / min, and the shielding gas flow rate is 35L / min.

[0016] The present invention has the following beneficial effects: Aiming at the impeller of a nuclear power seawater circulation pump with damaged surface, the laser cladding powder of the present invention is used for repairing the impeller of the seawater circulation pump, which can well improve the use function.

[0017] The method of the present invention adopts the laser cladding repair technology, and the outer surface is repaired by combining the repair of the same material as the substrate and the repair of the functional layer, so as to improve the use function.

[0018] The blades of the impeller usually have complex geometries, including free-form surfaces and regions with large curvature changes. Such complex surfaces result in frequent path changes during the cladding process. Additionally, the long and thin blades have poor rigidity during the cladding process and are prone to deformation, making it difficult to ensure the cladding accuracy. Repairing the complex surface of the damaged impeller according to the repair path and sequence designed in the present invention, through the methods of inter-region jump repair and double-sided symmetric repair, effectively avoids cracking of the repair layer and is conducive to controlling the deformation amount of the impeller substrate, achieving high-quality repair of the impeller of the nuclear power seawater circulation pump. The method of the present invention has high repair efficiency, and the repair layer has no defects such as pores, lack of fusion, and cracks, which can improve the corrosion resistance and wear resistance of the impeller of the nuclear power seawater circulation pump during service, and has broad engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope.

[0020] Figure 1 It is a schematic diagram of the impeller tooling assembly, where 1 is the impeller and 2 is the clamping tooling.

[0021] Figure 2 It is a schematic diagram of the cladding sequence and repair path of the impeller, where 3 is the cladding area 1, 4 is the cladding area 2, 5 is the cladding area 3, 6 is the cladding area 4, and 7 is the cladding area 5.

[0022] Figure 3 It is a physical diagram of the repaired impeller.

[0023] Figure 4 It is a macroscopic metallographic diagram of the cross-section of the repaired impeller. (a) is the low-magnification metallography, and (b) is the metallography of the interface between the substrate repair layer and the functional layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, unless otherwise stated, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0025] A method for laser cladding of an impeller of a seawater circulation pump may specifically be as follows: Before impeller repair, clean the surface impurities of the impeller substrate, and determine and mark the impeller defect information through non-destructive inspection.

[0026] Remove the surface defects of the impeller, clean the processing area and its surrounding areas, and conduct non-destructive inspection again.

[0027] Clean the surface of the impeller that has passed the non-destructive inspection without damage, and fix it with a tooling for assembly and reserve. For example, the impeller can be fixedly connected to a six-axis robotic arm or a two-axis positioner and controlled by an automated system.

[0028] Before repairing the impeller, dry the duplex stainless steel powder and nickel-based alloy powder.

[0029] Divide the position of the repair area, program point by point in areas according to the designed path, adopt a jump repair sequence, first perform single-sided cladding at the defect position, and then perform cladding on the other side in the same way. Leave a machining allowance of 0.5 - 1.0 mm on both sides, and perform double-sided multi-layer cladding repair on the impeller. Form two layers of duplex stainless steel cladding layers and one layer of nickel-based alloy functional cladding layer on the matrix of the impeller in sequence. The duplex stainless steel cladding layer uses duplex stainless steel powder as the cladding material, and the nickel-based alloy functional cladding layer uses nickel-based alloy powder as the cladding material.

[0030] Clad duplex stainless steel on the surface of the impeller, and the process parameters are: laser power 1600W, scanning speed 10mm / s, powder feeding rate 1r / min, overlapping rate 50%, powder feeding gas flow rate 7.5L / min, shielding gas flow rate 25L / min.

[0031] Clad nickel-based alloy on the surface of the duplex stainless steel cladding layer, and the process parameters are: laser power 1400W, scanning speed 10mm / s, powder feeding rate 0.5r / min, overlapping rate 50%, powder feeding gas flow rate 5.5L / min, shielding gas flow rate 35L / min.

[0032] After each layer of cladding, cool the workpiece to the interlayer temperature, and then perform the next layer of cladding. The interlayer temperature is 100 - 120°C. After completing the single-sided multi-layer cladding, complete the multi-layer cladding on the other side according to the same cladding sequence and cladding path.

[0033] After the impeller after double-sided cladding is cooled to room temperature, remove the tooling.

[0034] Perform machining on the repaired impeller to restore the dimensional requirements and roughness requirements.

[0035] Perform non-destructive and metallographic cross-section inspections on the machined impeller to meet the repair quality requirements.

[0036] Example 1 The material of the impeller in this example is EN1.4468. This example provides a method for laser cladding of a seawater circulation pump impeller, including the following steps: 1. Use anhydrous ethanol to clean the surface of the impeller to be repaired, and remove the impurities on the surface of the impeller that affect the repair.

[0037] 2. Inspect the impeller by visual, penetrant, and radiographic methods to determine the location, type, size, and quantity of the impeller defects, and make marks on the impeller surface.

[0038] 3. Adopt mechanical processing methods to remove the defects on the impeller surface. The removal range size should be slightly larger than the defect size. After processing, the surface roughness ≤ Ra6.3. Clean the processed area and its surrounding area with anhydrous ethanol. After drying, conduct visual, penetrant, and radiographic inspections on the surface to be repaired. After passing the inspection, clean the impeller surface again. After drying, assemble the impeller 1 and the clamping tooling 2 as Figure 1 shown, and fix it on the platform of the equipment's double-axis positioner for standby. The double-axis positioner is controlled by the kuka robot system.

[0039] 4. The repair method adopted is the coaxial laser cladding repair technology. The powder particle size is 53μm, and the powder feeding gas and protective gas are high-purity argon (purity ≥ 99.99%).

[0040] 5. Adopt a repair method that combines matrix repair and functional repair. The first and second layers are repaired with the same matrix material, which is a duplex stainless steel material; the third layer and above are repaired with a functional layer, which is a nickel-based alloy; Before laser cladding repair, take appropriate duplex stainless steel powder (EN1.4468) and nickel-based alloy powder (Inconel 625), place them in a vacuum drying oven, set the powder drying temperature to 120°C, and keep warm and dry for 2h.

[0041] The process parameters for matrix material repair are: laser power 1600W, scanning speed 10mm / s, powder feeding rate 1r / min, overlapping rate 50%, powder feeding gas flow rate 7.5L / min, and protective gas flow rate 25L / min.

[0042] The process parameters for functional layer repair are: laser power 1400W, scanning speed 10mm / s, powder feeding rate 0.5r / min, overlapping rate 50%, powder feeding gas flow rate 5.5L / min, and protective gas flow rate 35L / min.

[0043] As Figure 2 shown, the adopted repair sequence and path are: divide the repair positions for the area to be repaired. The arrow indicates the cladding sequence for a single cladding area. After determining the points, compile the cladding program. To avoid stress concentration, adopt a jump repair sequence. Conduct double-sided multi-layer cladding tests and single-sided cladding operations at the impeller defect positions according to the process parameters. After cladding one layer, wait for the workpiece to cool to the interlayer temperature (100 - 120°C) before cladding the next layer. The heat generated by the previous layer of cladding can preheat the next layer.

[0044] 6. After the temperature of the impeller has cooled to 100-120°C after single-sided multi-layer cladding, perform the multi-layer cladding operation on the other side. The cladding sequence, cladding path, and starting side are the same as those of the first-side cladding operation. A machining allowance of 0.5 mm to 1.0 mm is reserved on both sides. After the double-sided cladding of the impeller is completed and cooled to room temperature, remove the impeller tooling constraints.

[0045] 7. Machine the repaired impeller according to the design requirements to restore the impeller size. The transition between the repaired area and the matrix area is smooth and the surface is smooth. The roughness of the repaired area is ≤ Ra3.2 μm.

[0046] 8. Conduct visual, penetrant, and radiographic non-destructive inspections on the repaired area of the impeller. There are no cracks or lack of fusion defects in the repaired area and the surrounding area. The repaired impeller is as Figure 3 shown.

[0047] 9. Cut the cross-section of the repaired area of the impeller that has passed the non-destructive inspection, and observe the cross-sectional morphology through a metallurgical microscope. As Figure 4 shown, there are no cracks, pores, lack of fusion, etc. in the cladding layer, and the interface between the matrix repair layer and the functional layer is well bonded.

[0048] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A laser cladding powder, characterized in that: It is a nickel-based alloy powder used for impeller repair, which includes: C≤0.1wt%, Si≤0.5wt%, Cr 20.0~23.0wt%, Fe≤5.0wt%, Mo 8.0~10.0wt%, Nb 3.15~4.15wt%, and the balance is Ni.

2. The laser cladding powder according to claim 1, characterized in that: The particle size of the laser cladding powder is 53-150 μm.

3. A method for laser cladding of a seawater circulation pump impeller, characterized in that: The impeller is repaired by adopting a laser cladding method, using the laser cladding powder described in claim 1 or 2 as a cladding material.

4. The method for laser cladding of a seawater circulation pump impeller according to claim 3, characterized in that: A laser cladding method is adopted to sequentially form a duplex stainless steel cladding layer and a nickel-based alloy functional cladding layer on the substrate of the impeller. The duplex stainless steel cladding layer uses duplex stainless steel powder as the cladding material, and the nickel-based alloy functional cladding layer uses the laser cladding powder as the cladding material. The duplex stainless steel powder and the laser cladding powder need to be dried before cladding.

5. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: The duplex stainless steel powder and the substrate are made of the same material, and the duplex stainless steel powder includes: C≤0.03wt%, Si≤1wt%, Mn≤2wt%, P≤0.025wt%, S≤0.025wt%, Cr 24.5~26.5wt%, Ni 5.5~7wt%, Mo 2.5~3.5wt%, N 0.12~0.25wt%, O≤0.03wt%, and the balance is Fe.

6. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: Two layers of the duplex stainless steel cladding layer and one layer of the nickel-based alloy functional cladding layer are sequentially formed on the substrate of the impeller.

7. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: After each cladding layer, the workpiece is cooled to the interlayer temperature before the next cladding layer is carried out. The interlayer temperature is 100~120℃.

8. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: The defective position of the impeller is divided into repair positions, and a cladding program is compiled after positioning. A jump repair sequence is adopted to first perform single-side cladding at the defective position, and then perform cladding on the other side in the same manner, with a machining allowance of 0.5-1.0 mm reserved on both sides.

9. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: The laser power for forming the duplex stainless steel cladding layer is 1600 W, the scanning speed is 10 mm / s, the powder feeding rate is 1 r / min, the overlap rate is 50%, the powder feeding gas flow rate is 7.5 L / min, and the shielding gas flow rate is 25 L / min.

10. The method for laser cladding of a seawater circulation pump impeller according to claim 4, characterized in that: The laser power for forming the nickel-based alloy functional cladding layer is 1400 W, the scanning speed is 10 mm / s, the powder feeding rate is 0.5 r / min, the overlap rate is 50%, the powder feeding gas flow rate is 5.5 L / min, and the shielding gas flow rate is 35 L / min.

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