Plasma spraying method for preparing cobalt-molybdenum-chromium-silicon wear-resistant coating of heteromorphic rectifier blade

Abstract

The application discloses a plasma spraying preparation method of a cobalt-molybdenum-chromium-silicon wear-resistant coating of a special-shaped rectification vane, and comprises the following steps: S1, shielding and protecting a non-spraying area of a part after cleaning treatment, wherein a through hole is blocked by a silica gel plug, and a blind hole is filled and solidified by using ultraviolet light curing adhesive; S2, performing sand blasting roughening pretreatment on a surface to be sprayed; S3, after pretreatment of cobalt-molybdenum-chromium-silicon alloy powder, spraying the special-shaped rectification vane by using a plasma spraying device; and S4, after spraying is completed, removing the silica gel plug and placing the special-shaped rectification vane in a solidification furnace for heating, and removing the ultraviolet light curing adhesive by using a melting point difference between the special-shaped rectification vane and the ultraviolet light curing adhesive, so that the spraying efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of blade spraying technology, and particularly relates to a method for preparing a cobalt-molybdenum-chromium-silicon wear-resistant coating by plasma spraying on irregularly shaped rectifier blades. Background Technology

[0002] Cobalt-molybdenum-chromium-silicon coatings exhibit excellent wear resistance, fretting wear resistance, and corrosion resistance at high temperatures (above 800℃), and their ductility is superior to that of Co-WC coatings. They have been widely used in aero engines abroad, but there are only a few reports on the application of cobalt-molybdenum-chromium-silicon coatings.

[0003] The preparation of high-performance thermal spray coatings on the surface of engineering components hinges on two crucial factors: the spraying process and the structure of the components. Existing technology CN113373399A employs supersonic flame spraying to prepare cobalt-molybdenum-chromium-silicon coatings on single and simple structural surfaces. However, current technology lacks a dedicated plasma spraying process for cobalt-molybdenum-chromium-silicon coatings on U-shaped surfaces that simultaneously integrate blind holes and through holes, thus failing to meet the requirements for mass production and use of such irregularly shaped parts.

[0004] Therefore, the preparation of cobalt-molybdenum-chromium-silicon coatings by plasma spraying on complex U-shaped surfaces with holes is a technical task that urgently needs to be solved in industrial production. Summary of the Invention

[0005] In view of this, the present invention provides a self-locking borehole guide device for a certain type of engine flow channel component, which improves the spraying efficiency of the blades.

[0006] A method for preparing a cobalt-molybdenum-chromium-silicon wear-resistant coating by plasma spraying on an irregularly shaped rectifier blade, wherein the irregularly shaped rectifier blade has through holes and blind holes, comprising the following steps:

[0007] S1: After cleaning, the non-painted areas of the parts are masked and protected. The through holes are sealed with silicone plugs, and the blind holes are filled and cured with UV-curable adhesive. S2: Pre-treat the surface to be sprayed by sandblasting to roughen it; S3: After pretreatment, the cobalt-molybdenum-chromium-silicon alloy powder is placed in a plasma spraying equipment to spray the irregularly shaped rectifier blade. The plasma spraying equipment uses an internal powder feeding method to spray the cobalt-molybdenum-chromium-silicon alloy powder onto the surface of the irregularly shaped rectifier blade to be sprayed. During the spraying process, the air-cooling auxiliary system is turned on for cooling. S4: After spraying, remove the silicone plug and place the irregularly shaped rectifier blade in the curing oven for heating. Utilize the melting point difference between the irregularly shaped rectifier blade and the UV-curable adhesive to remove the UV-curable adhesive.

[0008] In one embodiment, the blind hole in S1 is filled and cured using a UV-curable adhesive, including... Inject UV-curable adhesive into the blind hole to form a cap; The cap is scraped off and made flush with the sprayed surface, and then cured by UV light.

[0009] In one embodiment, S2 includes, Use 60-mesh brown corundum abrasive, a sandblasting pressure of 0.25-0.35 MPa, and a sandblasting spacing of 100-150 mm to ensure that the surface roughness to be sprayed is 2-5 μm.

[0010] In one embodiment, the plasma spraying equipment in S3 has the following spraying process parameters: current 450-550A, voltage 60-70V, argon flow rate 40-60L / min, hydrogen flow rate 6-9L / min, spraying distance 100-140mm, and powder feeding rate 25-38g / min.

[0011] In one embodiment, the cold air distance of the air-cooled auxiliary system is 100-200mm, and the cold air pressure is 2-3.2MPa.

[0012] In one embodiment, the mass composition of the cobalt-molybdenum-chromium-silicon alloy powder is: Mo 27-29%, Cr 16-18%, Si 2.5-3.5%, with the balance being Co, and the powder particle size is 15-45 μm.

[0013] In one embodiment, the pretreatment of the cobalt-molybdenum-chromium-silicon alloy powder involves placing the powder in a vacuum drying oven and drying it at a constant temperature of 100-120°C for 1.5-2.5 hours.

[0014] In one embodiment, S4 includes, The curing oven is heated to 500±10℃ and held for 10-20 minutes to melt the UV-curable adhesive. After cooling, compressed air is used to blow away the brittle colloid.

[0015] In one embodiment, the U-shaped surface component is an irregularly shaped rectifier blade.

[0016] In one embodiment, after step S4, the coating has a bonding strength ≥70 MPa, a hardness ≥82 HR15 N, and a porosity <3%.

[0017] The beneficial effects of the present invention are as follows: Through holes are sealed with silicone plugs, and blind holes are filled and cured with UV-cured adhesive. After spraying, the difference in melting points between the part substrate and the adhesive is used for heating and embrittlement removal, which effectively solves the technical problem of powder entering the channel and causing powder accumulation at the orifice during plasma spraying of complex U-shaped parts with holes. This achieves coating-free blind and through holes. At the same time, the internal powder delivery plasma spraying method ensures that the powder is fully heated and completely melted in the core area with the highest plasma jet energy density, avoiding the defects of agglomerated oxides in the coating structure caused by external powder delivery. Combined with the air-cooling auxiliary system, the spraying process is simultaneously and uniformly cooled to reduce the temperature gradient and thermal stress concentration around the U-shaped curved surface and orifice, and synergistically eliminates coating delamination and cracking defects. Finally, a cobalt-molybdenum-chromium-silicon wear-resistant coating with a bonding strength ≥70 MPa, hardness ≥82HR15N, and porosity <3% is prepared on the surface of irregular parts, which significantly improves the uniformity, density and service reliability of the coating. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram showing a sprayed area including a non-sprayed area, where the non-sprayed area includes blind holes and through holes; Figure 3 Metallographic image of the blade processed in the steps of this invention. Detailed Implementation

[0020] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0021] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0022] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0023] See Figures 1 to 3 The method for preparing a cobalt-molybdenum-chromium-silicon wear-resistant coating by plasma spraying on a shaped rectifier blade, wherein the shaped rectifier blade has through holes and blind holes, includes the following steps: S1: After cleaning, the non-painted areas of the parts are masked and protected (in the U-shaped area of ​​the irregular rectifier blade, including non-painted areas such as through holes and blind holes). The through holes are sealed with silicone plugs, and the blind holes are filled and cured with UV-curable adhesive to facilitate subsequent overall painting. S2: Perform sandblasting roughening pretreatment on the surface to be sprayed to ensure the roughness of the substrate surface after spraying; S3: After pretreatment, the cobalt-molybdenum-chromium-silicon alloy powder is placed in a plasma spraying equipment to spray the irregularly shaped rectifier blade. The plasma spraying equipment uses an internal powder feeding method to spray the cobalt-molybdenum-chromium-silicon alloy powder onto the surface of the irregularly shaped rectifier blade to be sprayed. During the spraying process, the air-cooling auxiliary system is turned on for cooling. S4: After spraying, remove the silicone plug and place the irregularly shaped rectifier blade in the curing oven for heating. Utilize the melting point difference between the irregularly shaped rectifier blade and the UV-curable adhesive to remove the UV-curable adhesive.

[0024] The working principle is as follows: 1) Differentiated protection principle between blind holes and through holes During plasma spraying, the sprayed powder is jetted onto the workpiece surface at high speed. If blind holes and through holes are not protected, powder particles will directly enter the hole and deposit on the hole wall, leading to powder accumulation inside the hole, coating buildup at the hole opening, and even blockage of the hole. This invention addresses the structural differences between blind holes and through holes by employing different protection methods. For through holes, which are penetrating channels, a silicone plug matching the hole diameter is directly pressed into the through hole. The silicone plug relies on its own elasticity to form a tight fit with the hole wall, and the end face of the plug is flush with the spraying surface. During the spraying process, it can both prevent powder from entering the channel and prevent it from protruding from the hole opening, thus affecting the uniform flow of the spray jet.

[0025] Blind holes are closed-bottomed pits that cannot be sealed with plugs. This invention uses a UV-curable adhesive injected into the blind holes, which is then scraped to make the adhesive surface flush with the spraying surface. The adhesive is then fully cured by UV irradiation. The cured adhesive forms a dense protective layer at the hole opening, effectively preventing powder from entering the blind holes during spraying. After spraying, taking advantage of the significant melting point difference between the metal substrate of the part (melting point much higher than 1000℃) and the UV-curable adhesive (melting point approximately 500℃), the part is heated in a curing oven at 500±10℃. The adhesive becomes brittle at the high temperature and can then be easily blown away with compressed air, without any damage to the part substrate or the sprayed cobalt-molybdenum-chromium-silicon coating (operating temperature up to 800℃).

[0026] 2) Working principle of internal powder delivery plasma spraying Atmospheric plasma spraying (APS) works by inputting hundreds of amperes of current and tens of volts of electrical energy between the electrode (cathode) and the nozzle (anode). This energy is dissociated by the introduction of a gas (such as argon or hydrogen) to form plasma. The plasma jet reaches temperatures of 10,000-15,000 K, heating and melting the powder material, which is then sprayed onto the workpiece surface under high-speed gas flow to form a coating. The UnicoatPro atmospheric plasma spraying equipment used employs an internal powder feeding method. Traditional plasma spraying often uses an external powder feeding method, where the powder feeding pipe is located outside the nozzle end face, and the powder is fed in from outside the plasma jet. External powder feeding methods have disadvantages such as high energy consumption and low powder deposition efficiency. Furthermore, the powder entering from outside the jet is not sufficiently heated, and some powder fails to melt completely before impacting the substrate, resulting in a loose coating structure and the presence of agglomerated oxides.

[0027] This invention employs an internal powder feeding method, with the powder feeding hole located within the nozzle compression channel (2-6 mm from the nozzle outlet end face). The powder is directly fed into the core region of the plasma jet energy density, where it is rapidly heated and fully melted. This more thorough heating and complete melting of the powder is beneficial for forming a dense and uniform coating. At the same time, the powder deposition rate is higher, and the material and energy utilization rates are significantly improved. This avoids the defects of agglomerated oxides in the coating structure caused by uneven powder heating in external powder feeding methods.

[0028] 3) Synergistic mechanism of air-cooled auxiliary system During plasma spraying, the plasma flame temperature is extremely high (above 10,000K), and the instantaneous temperature rise in the sprayed area is drastic. For U-shaped parts with blind holes and through holes, the thermal stress concentration is more significant in the orifice area due to geometric discontinuity. If the cooling is insufficient or uneven, defects such as thermal stress cracks and coating delamination are easily generated at the orifice. In this invention, the air-cooling auxiliary system is activated simultaneously during the spraying process, and high-pressure cold air (pressure 23.2MPa) is continuously blown towards the sprayed area to achieve simultaneous spraying and cooling. Its working mechanism includes: (1) controlling the transient temperature of the substrate surface to avoid overheating and excessive thermal stress at the interface between the coating and the substrate; (2) accelerating the solidification of the deposited coating, refining the coating grain structure, and reducing the coating porosity; (3) uniform forced convection cooling can effectively reduce the temperature gradient of the U-shaped curved surface and the area around the orifice, and suppress cracks and delamination caused by thermal stress concentration. The optimized matching of air cooling distance (100-200mm) and air cooling pressure (2-3.2MPa) ensures a balance between cooling effect and coating quality. Excessive air cooling will cause the coating particles to not melt, while insufficient cooling will result in inadequate cooling and failure to eliminate thermal stress.

[0029] 4) Synergistic elimination mechanism of powder accumulation at orifice and coating defects The openings of blind and through holes are the most likely sites for coating defects to develop. During plasma spraying, the high-speed jet creates a flow effect around the opening edge, causing incompletely melted particles to accumulate and form "powder buildup." Simultaneously, thermal stress concentration in the opening area easily leads to coating delamination and cracking. This invention eliminates these defects through a synergistic effect on three levels: (1) In terms of channel protection, silicone plugs and UV-cured adhesive keep the orifice flat and prevent abnormal accumulation of powder at the edge of the orifice. (2) Powder melting layer: The internal powder feeding method ensures that the powder is fully melted, reducing the looseness and powder accumulation caused by unmelted particles hitting the matrix; (3) In terms of thermal stress control, the air-cooled auxiliary system provides uniform cooling, reducing the temperature gradient and thermal stress concentration in the orifice area. The three factors work together to achieve the technical effect of uniform and dense coating, no powder accumulation at the orifice, and no delamination or cracking.

[0030] Overall: Cobalt-molybdenum-chromium-silicon alloy powder is melted at high temperature by plasma spraying and then impacts the substrate at high speed. The molten particles rapidly spread and solidify on the substrate surface, stacking layer by layer to form a coating. Co, as a matrix element, provides good ductility and toughness; Mo and Cr form uniformly distributed Laves phase intermetallic compounds during solidification, providing high hardness and wear resistance; Si plays a role in deoxidation and improving wettability. This invention, through optimized plasma spraying process parameters, ensures that the powder is fully melted in the plasma jet and achieves optimal impact velocity and spreading state. It utilizes the melt difference to form a regional colloid without damaging the blade substrate surface, ultimately forming a high-quality coating with a bonding strength ≥70MPa, hardness ≥82HR15N, and porosity <3%.

[0031] For example: Step 1: The engineering part in this embodiment is an irregularly shaped rectifier blade, which has a small-diameter blind hole (diameter 2mm, depth 1.5mm) and a through hole (diameter 6mm, depth 2.5mm) on its U-shaped surface.

[0032] Step 2: Perform routine pre-treatment cleaning on the part surface, such as wiping the surface with a non-woven cloth dampened with acetone until clean and free of oil. Non-painted areas are protected using tape and rigid tooling. Through-hole protection: Select a silicone plug that matches the diameter of the through-hole and press it completely into the through-hole, ensuring that the end face of the plug is flush with the surrounding sprayed surface; Blind hole protection: Slowly inject UV-curable adhesive into the blind hole using a syringe until the adhesive level is slightly above the hole opening. Use a blade to scrape off excess adhesive along the sprayed surface to make the adhesive surface level with the surrounding sprayed surface. Place the part with the adhesive applied under a UV lamp for 8 minutes to cure. Pre-treat the area to be sprayed by sandblasting: Use 60-mesh brown corundum as abrasive, sandblasting pressure of 0.3MPa, and sandblasting spacing of 120mm. The surface roughness after treatment is 3μm.

[0033] Step 3: Fix the part on the rotary table and let it rotate with the rotary worktable at a speed of 90 revolutions per minute.

[0034] Step 4, Powder pretreatment: Select cobalt-molybdenum-chromium-silicon alloy powder with a mass composition of Mo 28%, Cr 17%, Si 3%, and the balance being Co. The powder particle size is 15-45μm. Place the powder in a vacuum drying oven and dry it at a constant temperature of 110℃ for 2 hours to remove the water vapor adsorbed by the powder.

[0035] Step 5: Place the dried composite powder in the spraying equipment and use the UnicoatPro atmospheric plasma spraying system with internal powder feeding. The powder is directly fed into the core area with the highest plasma jet energy density within the nozzle compression channel through the powder feeding port, resulting in rapid heating and complete melting. The spraying process parameters are: current 500A, voltage 65V, argon flow rate 50L / min, hydrogen flow rate 7.2L / min, spraying distance 120mm, and powder feeding rate 30g / min. Simultaneously, the air-cooling auxiliary system is activated, with a cold air distance of 150mm and a cold air pressure of 2.8MPa. Before spraying, check the sealing of the through holes by the silicone plugs and the sealing of the blind holes by the UV-cured adhesive.

[0036] Step 6: After spraying, remove the silicone plug and place the sprayed parts into the curing oven. Keep them at 500℃ for 15 minutes (the melting point of the adhesive) to make the UV-cured adhesive inside the blind holes brittle. Then air cool to room temperature and use compressed air to blow away the brittle adhesive inside the blind holes.

[0037] See Figure 3 As shown, the plasma-sprayed cobalt-molybdenum-chromium-silicon coating obtained in this embodiment has excellent microstructure, high hardness, and high bonding strength. Its average bonding strength is 78.9 MPa, average hardness is 84.1 HR15 N, porosity is <3%, there is no coating inside blind holes and through holes, no powder accumulation at the hole openings, and no delamination or cracking defects in the coating.

[0038] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for preparing a cobalt-molybdenum-chromium-silicon wear-resistant coating by plasma spraying on a shaped rectifier blade, wherein the shaped rectifier blade has through holes and blind holes, characterized in that, Includes the following steps: S1: After cleaning, the non-painted areas of the parts are masked and protected. The through holes are sealed with silicone plugs, and the blind holes are filled and cured with UV-curable adhesive. S2: Pre-treat the surface to be sprayed by sandblasting to roughen it; S3: After pretreatment, the cobalt-molybdenum-chromium-silicon alloy powder is placed in a plasma spraying equipment to spray the irregularly shaped rectifier blade. The plasma spraying equipment uses an internal powder feeding method to spray the cobalt-molybdenum-chromium-silicon alloy powder onto the surface of the irregularly shaped rectifier blade to be sprayed. During the spraying process, the air-cooling auxiliary system is turned on for cooling. S4: After spraying, remove the silicone plug and place the irregularly shaped rectifier blade in the curing oven for heating. Utilize the melting point difference between the irregularly shaped rectifier blade and the UV-curable adhesive to remove the UV-curable adhesive.

2. The method according to claim 1, characterized in that, The blind holes in S1 are filled and cured using a UV-curable adhesive. Inject UV-curable adhesive into the blind hole to form a cap; The cap is scraped off and made flush with the sprayed surface, and then cured by UV light.

3. The method according to claim 1, characterized in that, S2 includes, Use 60-mesh brown corundum abrasive, a sandblasting pressure of 0.25-0.35 MPa, and a sandblasting spacing of 100-150 mm to ensure that the surface roughness to be sprayed is 2-5 μm.

4. The method according to claim 1, characterized in that, The plasma spraying equipment in S3 has the following spraying process parameters: current 450-550A, voltage 60-70V, argon flow rate 40-60L / min, hydrogen flow rate 6-9L / min, spraying distance 100-140mm, and powder feeding rate 25-38g / min.

5. The method according to claim 4, characterized in that, The air-cooling auxiliary system has a cold air distance of 100-200mm and a cold air pressure of 2-3.2MPa.

6. The method according to claim 1, characterized in that, The mass composition of the cobalt-molybdenum-chromium-silicon alloy powder is: Mo 27-29%, Cr 16-18%, Si 2.5-3.5%, with the balance being Co, and the powder particle size is 15-45μm.

7. The method according to claim 6, characterized in that, The pretreatment of cobalt-molybdenum-chromium-silicon alloy powder involves placing the powder in a vacuum drying oven and drying it at a constant temperature of 100-120℃ for 1.5-2.5 hours.

8. The method according to claim 1, characterized in that, S4 includes, The curing oven is heated to 500±10℃ and held for 10-20 minutes to melt the UV-curable adhesive. After cooling, compressed air is used to blow away the brittle colloid.

9. The method according to claim 1, characterized in that, The U-shaped component is an irregularly shaped rectifier blade.

10. The method according to claim 1, characterized in that, After step S4, the coating has a bonding strength ≥70 MPa, a hardness ≥82 HR15 N, and a porosity <3%.

Images