Laser cladding repair process for corrosion perforation of sea water pump body

Abstract

The invention relates to a laser cladding repair process for a corrosion perforation of a sea water pump body, which comprises the following steps: S1, carrying out surface pretreatment on a corrosion perforation area of the pump body, removing an oxide layer and cleaning; s2, the pump body and the laser cladding powder are subjected to preheating treatment; s3, laser cladding powder is cladded on the corrosion perforation area layer by layer through laser in a synchronous powder feeding mode, the corrosion perforation area is filled with the laser cladding powder, and the machining allowance is reserved; s4, post-heat treatment is conducted on the pump body obtained after cladding is completed; s5, the pump body obtained in the step S4 is machined to a preset final size; according to the laser cladding repair process, a stress relief annealing process is set: firstly, the residual stress of the pump body is removed as much as possible; and secondly, the pump body cannot be influenced after heat treatment, and the performance of the pump body cannot be reduced. And according to the performance of the laser cladding layer, the room-temperature hardness is larger than or equal to 40 HRC, the bonding strength is larger than or equal to 470 MPa, and the pump body meets the needed performance of abrasion resistance, high strength and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the field of laser advanced manufacturing technology, and in particular to a laser cladding repair process for corroded perforated seawater pump bodies. Background Art

[0002] Seawater pumps are commonly used marine equipment. During the operation of seawater pumps, the pump body will be subject to seawater corrosion, sediment scouring, and working stress, and is easily corroded and perforated. If traditional repair methods (such as welding and patch welding) are used, it is easy to cause the expansion of the heat-affected zone, secondary corrosion, and insufficient bonding strength, which cannot meet the long-term use requirements of seawater pumps in high salt spray and high humidity environments. There are also existing technologies that use laser cladding to repair pump bodies, but they all ignore a very important point, that is, the deformation of the pump body during the repair process and how to eliminate residual stress. Another point is that the cladding powder material and cladding process are important components of laser cladding repair technology. If the design is unreasonable, it will not be able to adapt to the high chloride ion corrosion environment of the ocean, and it is also very easy to generate large tissue stress and thermal stress in the cladding position, which will lead to cracking. In addition, the service life of the pump body after repair cannot be guaranteed. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to overcome the deficiencies of the prior art and provide a laser cladding repair process for corrosion and perforation of a seawater pump body.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A laser cladding repair process for corrosion perforation of a seawater pump body comprises the following steps:

[0006] S1: Surface pretreatment of the corroded and perforated areas of the pump body to remove the oxide layer and clean it;

[0007] S2: preheating the pump body and laser cladding powder;

[0008] S3: Using a synchronous powder feeding method, laser cladding powder is clad layer by layer on the corrosion perforation area using a laser, so that the corrosion perforation area is filled and a machining allowance is reserved;

[0009] S4: Perform post-heat treatment on the pump body after cladding is completed;

[0010] S5: Processing the pump body obtained in step S4 to a preset final size;

[0011] The laser cladding powder is a mixture of tungsten carbide powder and nickel-based alloy powder, the mass ratio of the tungsten carbide powder to the nickel-based alloy powder is (85-80): (15-20), and the mass percentage of each element in the nickel-based alloy powder is: Ni 65%-73%, Cr 15%-18%, Mo 6%-8%, Nb 4%-6%, C≤0.3%, and the balance is Fe. The laser cladding powder can prevent the pump body from being corroded by the seawater environment after cladding.

[0012] Wherein, in step S3, the laser power is 800-1500W, the spot diameter is 1.0-2.0mm, the scanning speed is 5-15cm / min, and the powder feeding rate is 15-20g / min.

[0013] Furthermore, in the step S1, the surface of the corroded perforated area is pretreated by sandblasting, wherein aluminum oxide sand particles are used in the sandblasting, with a particle size of 80-120 mesh and a roughness of Ra=6.3-12.5 μm.

[0014] Furthermore, the step S2 includes: heating the laser cladding powder to 120-130° C. and keeping the temperature; heating the pump body to 450-500° C. and keeping the temperature.

[0015] Furthermore, the step S4 includes: placing the pump body after cladding in a furnace at 300-400° C. for 1-2 hours, and then cooling the furnace to 150° C. and then air cooling.

[0016] Furthermore, the particle size of the tungsten carbide powder is between 100-150 meshes, and the particle size of the nickel-based alloy powder is between 120-160 meshes.

[0017] Furthermore, in step S3, during laser cladding, the thickness of the cladding layer is 0.8-2.0 mm, and the temperature difference between layers is controlled between 80-120°C.

[0018] Furthermore, in step S3, a multi-axis robotic arm is used to control the movement of the laser head, and a path planning algorithm is generated based on the three-dimensional model of the pump body, with a trajectory error of <0.1 mm.

[0019] In the present invention, nickel element ensures the wettability of the cladding layer and the steel material. A fixed content of nickel element can make the cladding layer well bonded with the low-carbon steel matrix alloy and improve the corrosion resistance of the cladding layer.

[0020] The chromium element ensures the corrosion resistance of the cladding layer. The alloying element chromium is dissolved or alloyed into the middle of the coating during the formation of the cladding layer, and is extremely easily passivated in the air, forming a passivation layer on the surface of the coating, thereby improving the corrosion resistance of the coating.

[0021] The alloyed molybdenum element is dissolved or alloyed into the middle of the coating during the formation of the cladding layer, which can further strengthen the passivation layer formed by the element chromium and improve the seawater corrosion resistance of the cladding layer.

[0022] The element chromium significantly improves the strength and corrosion resistance of the alloy.

[0023] The carbon element ensures that the alloy cladding layer has sufficient hardness. During the alloy melting process, the carbon element easily forms an alloy compound with the iron element, which improves the hardness of the cladding layer.

[0024] The tungsten element improves the corrosion resistance of the coating formed by the alloy powder. Tungsten powder, carbon powder, and ferrochrome powder fully react during the laser cladding process to produce new hard phases. The formation of these new phases causes the physical structure in the coating to become finer and more evenly distributed, and the oxide film becomes denser and less susceptible to being cut. The formed oxide film has the function of isolating high-chloride ion corrosive liquid, thereby improving corrosion resistance. When the tungsten: chromium: carbon: iron content is within the ratio range of the formula of the present invention, the corrosion current of the coating is minimized and the corrosion resistance of the cladding layer is optimal. If the proportion of tungsten carbon powder is too large, more new phases will be generated, triggering crack initiation, causing the coating to lose its protective function and the substrate to be corroded.

[0025] The laser cladding repair process of the present invention has the following beneficial effects:

[0026] 1. The materials used in the laser cladding of the present invention are not limited to a certain alloy, but there are requirements for the alloy composition. In this way, the cladding material can be selected according to needs while ensuring its seawater corrosion resistance;

[0027] 2. Set the stress relief annealing process: first, remove the residual stress of the pump body as much as possible; second, ensure that the heat treatment will not affect the pump body and will not reduce the performance of the pump body.

[0028] 3. The performance of the laser cladding layer is room temperature hardness ≥ 40HRC, bonding strength ≥ 470MPa, and no rust on the surface after 168h of copper accelerated acetic acid salt spray (CASS) test, so that the pump body meets its working conditions and the required wear resistance, high strength and corrosion resistance. DETAILED DESCRIPTION

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "left", "right", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0030] The present invention provides a laser cladding repair process for corrosion perforation of a seawater pump body, which comprises the following steps:

[0031] S1: Surface pretreatment of the corroded and perforated areas of the pump body to remove the oxide layer and clean it;

[0032] S2: preheating the pump body and laser cladding powder;

[0033] S3: Using a synchronous powder feeding method, laser cladding powder is clad layer by layer on the corrosion perforation area using a laser, so that the corrosion perforation area is filled and a machining allowance is reserved;

[0034] S4: Perform post-heat treatment on the pump body after cladding is completed;

[0035] S5: Processing the pump body obtained in step S4 to a preset final size.

[0036] The laser cladding powder is a mixture of tungsten carbide powder and nickel-based alloy powder, with the mass ratio of the tungsten carbide powder to the nickel-based alloy powder being (85-80):(15-20), i.e., the mass percentage of tungsten carbide powder is 80-85%, and the mass percentage of nickel-based alloy powder is 15-20%. The mass percentages of the elements in the nickel-based alloy powder are as follows: Ni 65%-73%, Cr 15%-18%, Mo 6%-8%, Nb 4%-6%, C ≤ 0.3%, and the balance Fe. At this ratio, the laser cladding powder can prevent corrosion of the pump body in a seawater environment after cladding. Preferably, the particle size of the tungsten carbide powder is between 100-150 mesh, and the particle size of the nickel-based alloy powder is between 120-160 mesh.

[0037] Specifically, in step S1, the surface of the corroded perforated area is pretreated by sandblasting. Alumina sand particles with a particle size of 80-120 mesh and a roughness of Ra=6.3-12.5 μm are used in the sandblasting, which has a good rust removal effect.

[0038] Specifically, step S2 includes: heating the laser cladding powder to 120-130° C. and keeping it warm; heating the pump body to 450-500° C. and keeping it warm, so that the subsequent cladding effect is better and the bonding between the materials is tighter.

[0039] Specifically, in step S3, the laser power is 800-1500w, the spot diameter is 1.0-2.0mm, the scanning speed is 5-15cm / min, and the powder feeding rate is 15-20g / min. Preferably, in step S3, the thickness of the cladding layer during laser cladding is 0.8-2.0mm, and the temperature difference between layers is controlled between 80-120°C, so that the cladding effect of each layer is better. Preferably, in step S3, a multi-axis robotic arm is used to control the movement of the laser head, and the path planning algorithm is generated based on the three-dimensional model of the pump body, and the trajectory error is less than 0.1mm. The path planning algorithm of the multi-axis robotic arm ensures the accuracy of complex surface repair.

[0040] Specifically, step S4 involves placing the clad pump body in a furnace at 300-400°C for 1-2 hours, then cooling it to 150°C in the furnace and air-cooling it. This minimizes residual stress in the pump body and ensures that the heat treatment does not affect the pump body or degrade its performance.

[0041] The following are specific embodiments:

[0042] Example 1

[0043] Laser cladding technology was used to repair a corroded perforation with a diameter of 11 mm on a pump body made of CD6MN duplex stainless steel. The following steps were performed:

[0044] S1: Pre-treating the surface of the corroded and perforated area of ​​the pump body by sandblasting to remove the oxide layer and clean the surface; the sandblasting uses aluminum oxide sand with a particle size of 80 mesh and a roughness of Ra = 12.5 μm;

[0045] S2: Heat the laser cladding powder to 130°C and keep it warm; heat the pump body to 500°C and keep it warm.

[0046] S3: Laser cladding powder is applied layer by layer to the corroded perforated area using a synchronous powder feeding method, so that the corroded perforated area is completely filled and a machining margin is reserved. The mass ratio of tungsten carbide powder to nickel-based alloy powder is 80:20. The mass percentage of each element in the nickel-based alloy powder is:

[0047] Ni: 65%; Cr: 18%; Mo: 8%; Nb: 6%; C ≤ 0.3%, the balance is Fe;

[0048] The particle size of the tungsten carbide powder was 100 mesh, and the particle size of the nickel-based alloy powder was 120 mesh. The laser power was 800W, the spot diameter was 2.0mm, the scanning speed was 5cm / min, the powder feed rate was 15g / min, the cladding layer thickness was 0.8mm, and the interlayer temperature difference was controlled at 80°C.

[0049] S4: Place the cladding-finished pump body in a furnace at 400°C for 1 hour, then cool it to 150°C in the furnace and air-cool it.

[0050] S5: Processing the pump body obtained in step S4 to a preset final size.

[0051] The metallographic structure of the cladding area on the pump body obtained in Example 1 was tested, and it was observed that the formed coating was organized into a uniform, fine dendritic crystal structure. The tungsten alloy was surrounded by a nickel-based alloy with good plasticity, forming a tungsten particle reinforced nickel-based alloy, which was significantly different from the continuous skeleton of tungsten in traditional powder metallurgy tungsten alloy. The cladding layer had no cracks or holes, and the cladding layer was well bonded to the surface of the CD6MN duplex stainless steel pump body.

[0052] Example 2

[0053] Laser cladding technology was used to repair a 15mm diameter corroded perforation on a pump body made of S32760 duplex stainless steel. The following steps were performed:

[0054] S1: Pre-treating the surface of the corroded and perforated area of ​​the pump body by sandblasting to remove the oxide layer and clean the surface; the sandblasting uses aluminum oxide sand with a particle size of 120 mesh and a roughness of Ra = 6.3 μm;

[0055] S2: Heat the laser cladding powder to 120°C and keep it warm; heat the pump body to 450°C and keep it warm.

[0056] S3: Laser cladding powder is applied layer by layer to the corroded perforated area using a synchronous powder feeding method, so that the corroded perforated area is completely filled and a machining allowance is reserved. The mass ratio of tungsten carbide powder to nickel-based alloy powder is 85:15. The mass percentages of the elements in the nickel-based alloy powder are as follows:

[0057] Ni: 73%; Cr: 15%; Mo: 6%; Nb: 4%; C ≤ 0.3%, the balance is Fe;

[0058] The particle size of the tungsten carbide powder was 150 mesh, and the particle size of the nickel-based alloy powder was 160 mesh. The laser power was 1500W, the spot diameter was 1.0mm, the scanning speed was 15cm / min, the powder feed rate was 20g / min, the cladding layer thickness was 2mm, and the interlayer temperature difference was controlled at 120°C.

[0059] S4: Place the cladding-finished pump body in a furnace at 300°C for 2 hours, then cool it to 150°C in the furnace and air-cool it.

[0060] S5: Processing the pump body obtained in step S4 to a preset final size.

[0061] The metallographic structure of the cladding area on the pump body obtained in Example 2 was tested, and it was observed that the formed coating was organized into a uniform, fine dendritic crystal structure. The tungsten alloy was surrounded by a nickel-based alloy with good plasticity, forming a tungsten particle reinforced nickel-based alloy, which was significantly different from the continuous skeleton of tungsten in traditional powder metallurgy tungsten alloy. The cladding layer had no cracks or holes, and the cladding layer was well bonded to the surface of the S32760 duplex stainless steel pump body.

[0062] Example 3

[0063] Laser cladding technology was used to repair a 13mm corroded perforation on a 304 stainless steel pump body. The following steps were performed:

[0064] S1: Pre-treating the surface of the corroded perforated area of ​​the pump body by sandblasting to remove the oxide layer and clean the surface; the sandblasting uses aluminum oxide sand with a particle size of 100 mesh and a roughness of Ra = 10 μm;

[0065] S2: Heat the laser cladding powder to 125°C and keep it warm; heat the pump body to 470°C and keep it warm.

[0066] S3: Laser cladding powder is applied layer by layer to the corroded perforated area using a synchronous powder feeding method, so that the corroded perforated area is completely filled and a machining allowance is reserved. The mass ratio of tungsten carbide powder to nickel-based alloy powder is 83:17. The mass percentages of the elements in the nickel-based alloy powder are as follows:

[0067] Ni: 70%; Cr: 17%; Mo: 7%; Nb: 5%; C ≤ 0.3%, the balance is Fe;

[0068] The particle size of the tungsten carbide powder was 130 mesh, and the particle size of the nickel-based alloy powder was 140 mesh. The laser power was 1200W, the spot diameter was 1.5mm, the scanning speed was 10cm / min, the powder feed rate was 17g / min, the cladding layer thickness was 1.4mm, and the interlayer temperature difference was controlled at 100°C.

[0069] S4: Place the cladding-finished pump body in a furnace at 350°C for 1.5 hours, then cool it to 150°C in the furnace and air-cool it.

[0070] S5: Processing the pump body obtained in step S4 to a preset final size.

[0071] The metallographic structure of the cladding area on the pump body obtained in Example 3 was tested, and it was observed that the coating formed was organized into a uniform, fine dendritic crystal structure. The tungsten alloy was surrounded by a nickel-based alloy with good plasticity, forming a tungsten particle reinforced nickel-based alloy, which was significantly different from the continuous skeleton of tungsten in traditional powder metallurgy tungsten alloy. The cladding layer had no cracks or holes, and the cladding layer was well bonded to the surface of the 304 stainless steel pump body.

[0072] Experimental example

[0073] For Examples 1-3, room temperature hardness, bonding strength, and salt spray corrosion tests and inspections were conducted on the coatings. The test results are shown in Table 1. The surface performance of Examples 1-3 of the present invention after 168 hours of copper accelerated acetic acid salt spray (CASS) testing clearly shows that the coating performance of Examples 1-3 meets the requirements.

[0074] Table 1

[0075] Example Room temperature hardness / HRC Bonding strength / MPa Surface condition after 168h CASS test Example 1 42.1 485 No corrosion Example 2 40.5 477 No corrosion Example 3 41.1 501 No corrosion

[0076] After being repaired using the repair processes described in Examples 1-3 of the present invention, the seawater pump bodies were found to have a lifespan comparable to that of new units, significantly reducing spare part replacement costs. Compared to existing technologies, the repair process of the present invention is highly targeted, resulting in less deformation and residual stress during the repair process. The repaired bodies also exhibit improved wear resistance, bonding strength, and corrosion resistance.

[0077] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that variations and improvements are possible without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A laser cladding repair process for corrosion and perforation of a seawater pump body, characterized in that: The following steps are involved: S1: Surface pretreatment of the corroded and perforated areas of the pump body to remove the oxide layer and clean it; S2: preheating the pump body and laser cladding powder; S3: Using a synchronous powder feeding method, laser cladding powder is clad layer by layer on the corrosion perforation area using a laser, so that the corrosion perforation area is filled and a machining allowance is reserved; S4: Perform post-heat treatment on the pump body after cladding is completed; S5: Processing the pump body obtained in step S4 to a preset final size; The laser cladding powder is a mixture of tungsten carbide powder and nickel-based alloy powder, the mass ratio of the tungsten carbide powder to the nickel-based alloy powder is (85-80): (15-20), and the mass percentage of each element in the nickel-based alloy powder is: Ni 65%-73%, Cr 15%-18%, Mo 6%-8%, Nb 4%-6%, C≤0.3%, and the balance is Fe. The laser cladding powder can prevent the pump body from being corroded by the seawater environment after cladding. Wherein, in step S3, the laser power is 800-1500W, the spot diameter is 1.0-2.0mm, the scanning speed is 5-15cm / min, and the powder feeding rate is 15-20g / min.

2. The laser cladding repair process for corrosion and perforation of a seawater pump body according to claim 1 is characterized in that: In the step S1, the surface of the corroded perforated area is pretreated by sandblasting. Alumina sand particles with a particle size of 80-120 mesh and a roughness of Ra=6.3-12.5 μm are used in the sandblasting.

3. The laser cladding repair process for corrosion and perforation of a seawater pump body according to claim 1 is characterized in that: The step S2 includes: heating the laser cladding powder to 120-130° C. and keeping the temperature; heating the pump body to 450-500° C. and keeping the temperature.

4. The laser cladding repair process for corrosion and perforation of a seawater pump body according to claim 1 is characterized in that: The step S4 comprises: placing the pump body after cladding in a furnace at 300-400° C. for 1-2 hours, then cooling the furnace to 150° C. and then air cooling.

5. The laser cladding repair process for corrosion and perforation of a seawater pump body according to claim 1 is characterized in that: The particle size of the tungsten carbide powder is between 100-150 meshes, and the particle size of the nickel-based alloy powder is between 120-160 meshes.

6. The laser cladding repair process for corrosion and perforation of a seawater pump body according to claim 1 is characterized in that: In step S3, during laser cladding, the thickness of the cladding layer is 0.8-2.0 mm, and the temperature difference between layers is controlled between 80-120°C.

7. The laser cladding repair process for corrosion perforation of a seawater pump body according to any one of claims 1 to 6, characterized in that: In step S3, a multi-axis robotic arm is used to control the movement of the laser head. The path planning algorithm is generated based on the three-dimensional model of the pump body, and the trajectory error is less than 0.1 mm.