Preparation method of anti-erosion gradient coating

Abstract

The embodiment of the invention provides a preparation method of an anti-erosion gradient coating. The preparation method comprises the steps that a to-be-repaired area on the surface of a workpiece is subjected to cleaning and sand blasting treatment; the first powder, the second powder and the third powder are sequentially sprayed to the to-be-repaired area through the high velocity oxy-fuel spraying technology, and the gradient coating is prepared; the first powder, the second powder and the third powder all comprise hard alloy powder and base material powder made of the same material as the workpiece, the content of the hard alloy powder in the first powder is smaller than that of the hard alloy powder in the second powder, and the content of the hard alloy powder in the second powder is smaller than that of the hard alloy powder in the third powder; and after the workpiece is sprayed and naturally cooled, the surface of the sprayed workpiece is subjected to protection treatment. According to the method, the anti-erosion coating (gradient coating) can be prepared on the basis of hypersonic flame spraying. And under the action of the gradient coating, a compact coating with smaller tensile stress can be obtained, and the properties of erosion resistance, water erosion resistance and the like of the workpiece are improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure belong to the technical field of surface engineering, and particularly relate to a preparation method of an anti-erosion gradient coating. BACKGROUND

[0002] During the operation of a unit in a thermal power plant, components such as turbine blades work in harsh environments such as high temperature, high pressure, high speed or wet steam area, and are usually subjected to high-speed liquid droplet erosion, solid particle erosion and the like, causing the service life of the turbine components to be reduced. The traditional surface protection method for turbine blades has problems such as large tensile stress, easy peeling of hard alloy coating, and low efficiency, and a new surface protection method needs to be developed to improve the anti-erosion performance. According to the service requirements of the turbine blade, the turbine blade needs to have good anti-erosion performance, and a high-hardness coating is sprayed on the surface of the turbine blade by supersonic flame spraying as a protection.

[0003] Due to the high heat input between the substrate and the coating produced by the supersonic flame spraying technology, tensile stress is generated at the bonding surface, and it is difficult to obtain a high-quality anti-erosion coating. In order to improve the current situation that the coating prepared by various technologies has a large tensile stress and the anti-erosion performance is reduced, a new anti-erosion coating preparation technology needs to be developed. SUMMARY

[0004] Embodiments of the present disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a preparation method of an anti-erosion gradient coating.

[0005] In one aspect of embodiments of the present disclosure, a preparation method of an anti-erosion gradient coating is provided, comprising:

[0006] cleaning and sandblasting the to-be-repaired area on the surface of the workpiece;

[0007] spraying a first powder, a second powder and a third powder on the to-be-repaired area in sequence by using a supersonic flame spraying process to prepare a gradient coating; the first powder, the second powder and the third powder each comprise hard alloy powder and substrate powder of the same material as the workpiece, wherein the content of the hard alloy powder in the first powder is less than the content of the hard alloy powder in the second powder, and the content of the hard alloy powder in the second powder is less than the content of the hard alloy powder in the third powder;

[0008] after the workpiece is naturally cooled after spraying is completed, the workpiece surface after the spraying treatment is protected.

[0009] Optionally, the particle size of the hard alloy powder and the substrate powder is 10-50 microns.

[0010] Optionally, the first powder comprises 50wt% cemented carbide and 50wt% base material powder; the second powder comprises 80wt% cemented carbide and 20wt% base material powder; and the third powder comprises 90wt% cemented carbide and 10wt% base material powder.

[0011] Optionally, the first powder is sprayed on the area to be repaired by using the high-velocity oxygen fuel spraying process, and a 50wt% cemented carbide-base material coating with a thickness of 50-60 microns is obtained on the area to be repaired.

[0012] Optionally, the second powder is sprayed on the 50wt% cemented carbide-base material coating by using the high-velocity oxygen fuel spraying process, and an 80wt% cemented carbide-base material coating with a thickness of 50-60 microns is formed.

[0013] Optionally, the third powder is sprayed on the 80wt% cemented carbide-base material coating by using the high-velocity oxygen fuel spraying process, and a 90wt% cemented carbide-base material coating with a thickness of 50-60 microns is formed to prepare a gradient coating.

[0014] Optionally, the process parameters in the high-velocity oxygen fuel spraying process include: oxygen fuel ratio 0.8, propane 30FMR, air 35FMR, powder feeding amount 45g / min, and the distance between the spray gun and the workpiece surface is 20mm.

[0015] Optionally, after the gradient coating is prepared by sequentially spraying the first powder, the second powder and the third powder on the area to be repaired by using the high-velocity oxygen fuel spraying process, the method further comprises: stopping spraying when the thickness of the gradient coating exceeds 0.2mm of the original workpiece surface.

[0016] Optionally, the cemented carbide powder comprises WC-17Co powder or WC-17Ni powder; and the base material powder comprises 15Cr12WMoV powder or 20Cr13 powder.

[0017] Optionally, after the workpiece spraying is naturally cooled, before the surface of the workpiece after the spraying treatment is protected, the method further comprises: grinding the gradient coating to restore the surface of the gradient coating to the original profile of the workpiece.

[0018] The beneficial effects of the embodiments of the present disclosure include:

[0019] In the present disclosure, the anti-erosion coating (gradient coating) can be prepared based on the high-velocity oxygen fuel spraying by using the above method. Under the action of the gradient coating, a dense coating with small tensile stress can be obtained, and the anti-erosion, anti-water erosion and other properties of the workpiece can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1A flowchart of a preparation method of an anti-erosion gradient coating for an embodiment of the present disclosure;

[0021] Figure 2 A structural diagram of a preparation process of an anti-erosion gradient coating for an embodiment of the present disclosure; wherein the manufacturing process of the gradient coating formed by spraying the workpiece with the spray gun is shown. DETAILED DESCRIPTION

[0022] In order for those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in combination with the drawings and specific embodiments.

[0023] The embodiments of the present application will be further described in detail below in combination with the drawings and embodiments. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, i.e., the present application is not limited to the described embodiments. In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error.

[0024] In the description of the present application, it should also be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] As shown in Figure 1 A preparation method of an anti-erosion gradient coating, comprising:

[0026] S101, cleaning and sandblasting the to-be-repaired area of the surface of the workpiece. The workpiece includes a turbine blade.

[0027] S102, sequentially spray the first powder, the second powder and the third powder on the to-be-repaired area by using a high-velocity oxygen fuel spraying process to prepare a gradient coating; the first powder, the second powder and the third powder all comprise cemented carbide powder and substrate powder of the same material as the workpiece, wherein the content of the cemented carbide powder in the first powder is less than the content of the cemented carbide powder in the second powder, and the content of the cemented carbide powder in the second powder is less than the content of the cemented carbide powder in the third powder.

[0028] S103, after the workpiece is naturally cooled after the spraying is completed, the surface of the workpiece after the spraying treatment is protected.

[0029] In the present disclosure, the mass content of the cemented carbide in the gradient coating is different, the mass content of the cemented carbide in each coating of the gradient coating gradually increases from the bottom to the surface, that is, the closer to the surface of the workpiece substrate, the less the mass content of the cemented carbide in the coating, and the farther away from the surface of the workpiece substrate, the more the mass content of the cemented carbide in the coating, and the composition of the coating with different mass contents of the cemented carbide comprises cemented carbide and a material of the same material as the workpiece.

[0030] In the present disclosure, the anti-erosion coating (gradient coating) can be prepared based on the high-velocity oxygen fuel spraying by using the above method. Under the action of the gradient coating, a dense coating with small tensile stress can be obtained, and the anti-erosion, anti-water erosion and other properties of the workpiece are improved.

[0031] In some embodiments, the particle size of the cemented carbide powder and the substrate powder is 10-50 microns.

[0032] In some embodiments, the first powder comprises 50wt% cemented carbide and 50wt% substrate powder; the second powder comprises 80wt% cemented carbide and 20wt% substrate powder; and the third powder comprises 90wt% cemented carbide and 10wt% substrate powder.

[0033] In some embodiments, the first powder is sprayed on the to-be-repaired area by using a high-velocity oxygen fuel spraying process, and a 50wt% cemented carbide-substrate coating with a thickness of 50-60 microns is obtained on the to-be-repaired area.

[0034] In some embodiments, the second powder is sprayed on the 50wt% cemented carbide-substrate coating by using a high-velocity oxygen fuel spraying process, and an 80wt% cemented carbide-substrate coating with a thickness of 50-60 microns is formed.

[0035] In some embodiments, the third powder is sprayed on the 80wt% cemented carbide-substrate coating by using a high-velocity oxygen fuel spraying process, and a 90wt% cemented carbide-substrate coating with a thickness of 50-60 microns is formed to prepare a gradient coating.

[0036] In some embodiments, the process parameters in the HVOF process include: oxygen fuel ratio 0.8, propane 30 FMR, air 35 FMR, powder feeding rate 45 g / min, and the distance between the spray gun and the surface of the workpiece is 20 mm.

[0037] In some embodiments, after the gradient coating is prepared by sequentially layering and spraying the first powder, the second powder and the third powder on the area to be repaired using the HVOF process, the method further comprises: stopping the spraying when the thickness of the gradient coating exceeds 0.2 mm of the original surface of the workpiece.

[0038] In some embodiments, the cemented carbide powder comprises WC-17Co powder or WC-17Ni powder; and the substrate powder comprises 15Cr12WMoV powder or 20Cr13 powder.

[0039] In some embodiments, after the workpiece is naturally cooled after the spraying is completed, before the surface of the workpiece after the spraying is protected, the method further comprises: grinding the gradient coating to restore the surface of the gradient coating to the original profile of the workpiece.

[0040] In one embodiment of the present disclosure, the workpiece is a turbine blade, which comprises:

[0041] In the present disclosure, the first layer of cemented carbide is designed to have a composition of 50wt%, the same substrate composition of the turbine blade is designed to have a composition of 50wt%, and the thickness of the first layer is designed to be 50-60 microns. The second layer of cemented carbide is designed to have a composition of 80wt%, the same substrate composition of the turbine blade is designed to have a composition of 20wt%, and the thickness of the second layer is designed to be 50-60 microns. The third layer of cemented carbide is designed to have a composition of 90wt%, the same substrate composition of the turbine blade is designed to have a composition of 10wt%, and the thickness of the third layer is designed to be 50-60 microns.

[0042] Specifically, the method comprises the following steps:

[0043] Step 1: The area to be repaired is subjected to oil removal treatment (cleaning treatment), and the area to be repaired is treated by mechanical polishing, and is subjected to sand blasting treatment, so that the surface roughness Ra reaches 10-300 microns, and the surface of the workpiece presents a rough state without metallic luster.

[0044] Step 2: The first powder, the second powder and the third powder are configured. The powder of the same material as the turbine blade is used as the gradient coating component, and the particle size of the powder is 10-50 microns. The first powder is composed of 50wt% cemented carbide and 50wt% substrate powder, the second powder is composed of 80wt% cemented carbide and 20wt% substrate powder, and the third powder is composed of 90wt% cemented carbide and 10wt% substrate powder.

[0045] Step 3: The first powder, the second powder and the third powder are sequentially sprayed on the surface of the turbine blade in the area to be repaired by using the supersonic flame spraying process, and sequentially obtain a 50wt% hard alloy-substrate coating with a thickness of 50-60 microns, an 80wt% hard alloy-substrate coating with a thickness of 50-60 microns, and a 90wt% hard alloy-substrate coating with a thickness of 50-60 microns on the surface of the turbine blade.

[0046] The process parameters in the supersonic flame spraying process are as follows: oxygen fuel ratio 0.8, propane 30FMR, air 35FMR, powder feeding amount 45g / min, and the distance between the spray gun and the workpiece surface is 20mm.

[0047] Step 4: After the spraying is completed, the workpiece is naturally cooled, and the surface of the treated workpiece is protected by a plastic film to prevent moisture absorption and pollution of the treated surface.

[0048] Through the above method, an anti-erosion coating can be prepared based on supersonic flame spraying. Under the action of the gradient coating, a dense coating with small tensile stress can be obtained, and the anti-erosion and anti-water erosion properties of the turbine blade are improved.

[0049] The present disclosure has the following advantages:

[0050] 1) The thermal stress caused by the difference in thermal expansion coefficient between the coating and the substrate is reduced, and the bonding strength and fatigue performance of the coating are improved.

[0051] 2) The continuous change of the metal and ceramic components and the gradient transition of the structure are realized, thereby improving the hardness, anti-erosion, anti-water erosion and other properties, and prolonging the service life of the turbine blade.

[0052] Reference Figure 2 The present disclosure provides specific examples, including:

[0053] Example 1: A coating is prepared on the surface of a 20Cr13 stainless steel part (workpiece). WC-17Co powder (hard alloy powder) and 20Cr13 powder (substrate powder) are used as the spraying material. Before repair, the 20Cr13 stainless steel substrate in the area to be repaired is subjected to oil removal, rust removal and sand blasting treatment to obtain a rough surface state. 50wt% WC-17Co and 50wt% 20Cr13 stainless steel powder are used as the first powder, 80wt% WC-17Co and 20wt% 20Cr13 stainless steel powder are used as the second powder, and 90wt% WC-17Co and 10wt% 20Cr13 stainless steel powder are used as the third powder.

[0054] The first powder, the second powder and the third powder are sprayed in sequence on the surface of the workpiece at the repair area by using the supersonic flame spraying process, and 50wt% WC-17Co coating with a thickness of 50-60 microns, 80wt% WC-17Co coating with a thickness of 50-60 microns and 90wt% WC-17Co coating with a thickness of 50-60 microns are obtained on the surface of the workpiece in sequence.

[0055] The process parameters used in spraying are as follows: oxygen fuel ratio 0.8, propane 30FMR, air 35FMR, powder feeding amount 45g / min, and distance 20mm. Spraying is stopped until the coating thickness of the repair area exceeds the original workpiece surface by about 0.2mm, and then the original profile of the repair area is restored by using mechanical grinding. After section metallographic detection, the sprayed area is dense and no cracks and other defects are generated.

[0056] In example 2, coating is prepared on the surface of a 15Cr12WMoV stainless steel part (workpiece). WC-17Ni powder (hard alloy powder) and 15Cr12WMoV powder (base material powder) are used as the spraying material. Before repair, the repair area of the 15Cr12WMoV workpiece substrate is subjected to oil removal (cleaning treatment), rust removal and sand blasting treatment to obtain a rough surface state. 50wt% WC-17Ni and 50wt% 15Cr12WMoV base material powder are used as the first powder, 80wt% WC-17Ni and 20wt% 15Cr12WMoV base material powder are used as the second powder, and 90wt% WC-17Ni and 10wt% 15Cr12WMoV base material powder are used as the third powder.

[0057] The first powder, the second powder and the third powder are sprayed in sequence on the surface of the workpiece at the repair area by using the supersonic flame spraying process, and 50wt% WC-17Ni coating with a thickness of 50-60 microns, 80wt% WC-17Ni coating with a thickness of 50-60 microns and 90wt% WC-17Ni coating with a thickness of 50-60 microns are obtained on the surface of the workpiece in sequence.

[0058] The process parameters used in spraying are as follows: oxygen fuel ratio 0.8, propane 30FMR, air 35FMR, powder feeding amount 45g / min, and distance 20mm. Spraying is stopped until the coating thickness of the repair area exceeds the original workpiece surface by about 0.2mm. Then the original profile of the repair area is restored by using mechanical grinding. After section metallographic detection, the sprayed area is dense and no cracks and other defects are generated.

[0059] From the above examples, the present disclosure provides a preparation method of an anti-erosion gradient coating, which adopts supersonic flame spraying to prepare a multilayer structure hard alloy-stainless steel gradient coating with different mass contents of hard alloy on the surface of a steam turbine blade, and the mass content of hard alloy in the coating with different mass contents gradually increases from the inside to the surface. Compared with the prior art, the gradient coating prepared by the present application eliminates the obvious interlayer interface of the layered structure, reduces the residual tensile stress in the coating, improves the microhardness of the coating, and is beneficial to improving the anti-erosion and water-erosion performance of the coating.

[0060] The computer readable medium can be included in the device, equipment or system of the present application, or can exist independently.

[0061] The computer readable storage medium can be any tangible medium that contains or stores a program, which can be an electrical, magnetic, optical, electromagnetic, infrared, semiconductor system, device or equipment, and more specific examples include, but are not limited to, an electrical connection with one or more wires, a portable computer diskette, a hard disk, an optical fiber, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0062] The computer readable storage medium can also include a data signal propagating in a baseband or as part of a carrier wave, in which computer readable program codes are carried, and specific examples include, but are not limited to, an electromagnetic signal, an optical signal, or any suitable combination thereof.

[0063] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the present disclosure.

Claims

1. A method for preparing an erosion-resistant gradient coating, characterized in that, include: The area to be repaired on the surface of the workpiece is cleaned and sandblasted. A gradient coating is prepared by sequentially spraying a first powder, a second powder, and a third powder onto the area to be repaired using a supersonic flame spraying process. The first powder, the second powder, and the third powder all include cemented carbide powder and a substrate powder of the same material as the workpiece. The cemented carbide powder content in the first powder is less than that in the second powder, and the cemented carbide powder content in the second powder is less than that in the third powder. After the workpiece has cooled naturally after the spraying is completed, a protective treatment is applied to the surface of the sprayed workpiece.

2. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, The particle size of both the cemented carbide powder and the substrate powder is 10-50 micrometers.

3. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, The first powder comprises 50 wt% cemented carbide and 50 wt% substrate powder; the second powder comprises 80 wt% cemented carbide and 20 wt% substrate powder; and the third powder comprises 90 wt% cemented carbide and 10 wt% substrate powder.

4. The method for preparing an erosion-resistant gradient coating according to claim 3, characterized in that, The first powder is sprayed onto the area to be repaired using a supersonic flame spraying process, resulting in a 50wt% cemented carbide-substrate coating with a thickness of 50-60 micrometers.

5. The method for preparing an erosion-resistant gradient coating according to claim 4, characterized in that, The second powder is sprayed onto the 50wt% cemented carbide-substrate coating using a supersonic flame spraying process, forming an 80wt% cemented carbide-substrate coating with a thickness of 50-60 micrometers.

6. The method for preparing an erosion-resistant gradient coating according to claim 5, characterized in that, A gradient coating is prepared by spraying a third powder onto an 80wt% cemented carbide-substrate coating using a supersonic flame spraying process to form a 90wt% cemented carbide-substrate coating with a thickness of 50-60 micrometers.

7. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, The process parameters for supersonic flame spraying include: oxygen-fuel ratio 0.8, propane 30FMR, air 35FMR, powder feed rate 45g / min, and distance between the spray gun and the workpiece surface 20mm.

8. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, After the supersonic flame spraying process is used to sequentially layer and spray the first powder, the second powder, and the third powder onto the area to be repaired to prepare a gradient coating, the process further includes stopping the spraying after the thickness of the gradient coating exceeds 0.2 mm above the original workpiece surface.

9. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, The cemented carbide powder includes WC-17Co powder or WC-17Ni powder; the substrate powder includes 15Cr12WMoV powder or 20Cr13 powder.

10. The method for preparing an erosion-resistant gradient coating according to claim 1, characterized in that, After the workpiece has finished spraying and cooled naturally, before applying a protective treatment to the surface of the sprayed workpiece, the process further includes: grinding the gradient coating to restore the surface of the gradient coating to the original shape of the workpiece.

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