Thin-wall special-shaped metal sealing ring surface toughening CoMoCrSi coating

Abstract

According to the thin-wall special-shaped metal sealing ring surface toughening CoMoCrSi coating, a double-layer glow plasma surface metallurgy technology is utilized, a CoMoCrSi alloy serves as a target material, a nickel-based high-temperature alloy thin-wall special-shaped metal sealing ring serves as a workpiece, and the thin-wall special-shaped metal sealing ring surface toughening CoMoCrSi coating is obtained through three steps. The method comprises the following steps: 1, regulating and controlling surface micro-area plastic deformation of a metal sealing ring by controlling current density, and realizing gradient change of roughness from a boundary to a center by virtue of an edge effect; secondly, remelting of the protruding position of the plastic deformation area is caused through the hollow cathode effect, target material element diffusion is accelerated, and interface mechanical-metallurgical bonding is achieved; and thirdly, the surface toughening CoMoCrSi coating with the gradient structure is formed through deposition. The mechanical occlusion depth between the coating and a workpiece is 2-6 microns, the thickness of a deposition layer is 10-30 microns, the thickness of a metallurgical diffusion layer is 1-5 microns, and the coating is high in toughness, simple and convenient in process, high in production efficiency, low in cost and suitable for batch processing.

Description

Technical Field

[0001] This invention relates to a toughened CoMoCrSi coating on the surface of a thin-walled irregularly shaped metal sealing ring, specifically belonging to the field of wear-resistant and corrosion-resistant technology for aero-engine components. Background Technology

[0002] Advanced mechanical seal technology determines the operational safety and efficiency of aero-engines. Metal sealing rings, as crucial aero-engine components, directly impact fuel efficiency and thrust-to-weight ratio through their sealing performance. Currently in service, metal sealing rings have irregular cross-sections, including C-shaped, U-shaped, Ω-shaped, and W-shaped profiles, formed by rolling thin strips of high-temperature alloys. Figure 1 Metal sealing rings are primarily installed between flanges, exhibiting excellent resilience and self-tightening properties under high-intensity vibration conditions. When engine operating conditions change, relative movement occurs between the locating teeth and the sealing ring's locating groove. Combined with mechanical vibration and thermal cycling, high-temperature fretting wear between the flange and the sealing ring can lead to ring failure. In severe cases, it can even wear through the thin wall of the metal sealing ring, reducing sealing effectiveness and impacting engine efficiency. Leakage in the metal sealing ring's sealing structure is one of the factors affecting gas flow within the leakage channel of the engine's metal sealing ring gap. Gas flow within the leakage channel is affected by surface roughness, with significant backflow occurring near rough surfaces, reducing the leakage velocity of the fluid within the channel. Under constant contact stress, the leakage of the sealing gap increases with increasing surface roughness; therefore, reducing the surface roughness of the coating can enhance its sealing performance.

[0003] Preparing a wear-resistant coating on the main sealing surface of the sealing ring is one of the effective methods to improve the wear resistance of the part surface. Cobalt-based materials have advantages such as good heat resistance, wear resistance, corrosion resistance, and oxidation resistance. Among them, the high-temperature stability of the CoMoCrSi coating is due to the addition of refractory alloying elements such as Mo, Co, and Cr, and it can be used stably for a long time at up to 800℃. The microstructure of the coating consists of primary Laves phase and eutectic structure, with strip-shaped secondary Laves phase appearing on the Co-rich solid solution. The Laves phase is an AB2-type close-packed hexagonal compound of Co, Mo, and Si, such as Mo2Co3Si or CoMoSi, which provides excellent wear resistance. The high Cr content in the CoMoCrSi coating can form a Cr2O3 protective layer on the workpiece surface that is resistant to corrosion by alkaline metal sulfates such as Na2SO4. In addition, Cr exists simultaneously in the cobalt-based solid solution and the Laves phase and is uniformly distributed, which ensures good corrosion resistance. CoMoCrSi is mainly deposited on the outer surface of the metal sealing ring, which improves the metal sealing ring's resistance to high-temperature sliding wear and high-temperature corrosion. It plays an important role in improving the sealing performance of the metal sealing ring and extending the service life of the metal seal.

[0004] Current research on the preparation of CoMoCrSi coatings using high-temperature alloys includes: * **Wear-resistant and Corrosion-resistant Alloy Coating for Aero-engine Sealing Supports and its Preparation** (CN114075643A). This patent prepares a CoMoCrSi coating on the surface of GH907 using thermal spraying. The residual stress generated during coating deposition causes varying degrees of deformation in the workpiece, especially for thin-walled workpieces. Once deformed, this deformation is difficult to correct mechanically or manually, thus affecting product quality and service life. Another method for preparing a cobalt-molybdenum-chromium-silicon amorphous coating (CN113373399A) involves supersonic flame spraying, where the immense heat and supersonic powder beam exert significant loads on the workpiece. Combined with the pre-spraying sandblasting roughening treatment, this can cause irreversible deformation of thin-walled workpieces. Currently, most CoMoCrSi coating preparations focus on thermal spraying (see "Performance of Plasma-Sprayed CoMoCrSi Coatings and Their Application in Aero-engines"). However, when spraying CoMoCrSi coatings onto thin-walled parts such as metal sealing rings, surface roughening before spraying, molten powder impact during spraying, and rapid cooling after spraying can all cause deformation of the thin-walled parts. Furthermore, element oxidation in the atmospheric spraying environment can affect coating quality. In contrast, CoMoCrSi coatings prepared by laser cladding offer advantages due to the high energy density and rapid cooling and heating rates of lasers, with cooling rates reaching up to 10... 3 ~10 6 The temperature of ℃ / s caused cracks at the interface between the coating and the substrate, and the irregular cross-sections such as the metal sealing ring also increased the difficulty of coating preparation ("Microstructure and mechanical properties of laser melting deposition of Tribaloy T-800 / WC composite coating on DZ125 alloy surface").

[0005] Double-layer glow discharge plasma surface metallurgy is a metal surface plasma metallurgy technology that has been applied and promoted based on ion nitriding technology. It is a novel material surface coating technology that mainly utilizes the principles of gas physical discharge, sputtering, and ion diffusion. Under vacuum conditions, efficient coating deposition is achieved in the anode chamber through the hollow cathode effect between the cathode (workpiece electrode) and the target electrode (source electrode). (See...) Figure 2In light of the above factors, this invention addresses the issues of workpiece deformation and excessively high surface roughness (>Ra 6.3) when CoMoCrSi coatings are prepared on the surface of thin-walled, irregularly shaped metal sealing rings. It proposes a method for preparing toughened CoMoCrSi coatings suitable for thin-walled, irregularly shaped metal sealing rings. This method utilizes the plasma edge effect to geometrically reconstruct the surface of the metal sealing ring, forming a mechanical interlock. The hollow cathode effect allows for remelting of the micro-plastic deformation region, resulting in a metallurgical bond between the CoMoCrSi coating and the metal sealing ring surface, thus achieving coating toughening. Currently, similar research on coating preparation using double-layer glow discharge plasma surface metallurgy technology includes: a NiCrAlSi / CeO2-doped YSZ thermal barrier coating and its preparation method (CN109207917B). This method prepares a NiCoCrAlY bonding layer followed by a multi-arc ion plating method to prepare a lubricating coating. However, it cannot utilize a hollow cathode to achieve metallurgical bonding between the substrate and coating interface, thereby improving interfacial adhesion. The NiCoCrAlSi / ZrO2 composite coating and its preparation method on the surface of γ-TiAl alloy (CN105839061B) achieves metallurgical bonding by Zr-O co-diffusion to satisfy the elemental gradient structure. However, without selective geometric reconstruction of the workpiece surface, a mechanical-metallurgical bond cannot be formed. The double-layer glow discharge plasma surface metallurgy technology prepares CoMoCrSi coatings in a vacuum chamber, achieving high sputtering yields of Mo and Si elements at sputtering temperatures of 750℃~850℃. Figure 3 This makes it easier for Co, Mo and Si to form close-packed hexagonal compounds Co3Mo2Si or CoMoSi phases, which improve the wear resistance of the coating. Therefore, the target material composition design is different from the powder composition of thermal spraying and laser cladding.

[0006] Currently, the coating interfaces formed by the publicly disclosed double-layer glow discharge plasma surface metallurgy technology in the field of coating structure are all flat layers, without demonstrating mechanical interlocking effect. To address the issues of easy deformation and poor adhesion of CoMoCrSi coatings on the surface of thin-walled irregularly shaped metal sealing rings, this invention proposes a workpiece surface geometric reconstruction method. This method achieves micro-regional plastic deformation through plasma bombardment, and improves the coating / workpiece adhesion through a combined mechanical-metallurgical action, with a mechanical interlocking depth of 2~6μm. The edge effect is used to geometrically reconstruct the surface of the metal sealing ring, achieving a gradient change in roughness from the boundary to the center. The roughness is high in the edge region and low in the center region (< Ra 3.2). The coating deposition thickness is 10~30μm, and the metallurgical diffusion layer is 1~5μm. A dual-layer glow discharge plasma surface metallurgy technique was employed to achieve coating toughening through a three-step process. The first step, surface geometry reconstruction, controlled the current density to regulate micro-regional plastic deformation on the surface of the metal sealing ring, achieving a roughness gradient from the boundary to the center through edge effects. The second step, a mechanical-metallurgical bonding process, utilized the hollow cathode effect to induce remelting at the protruding locations in the plastic deformation region, accelerating the diffusion of target elements and achieving interfacial mechanical-metallurgical bonding. The third step, deposition, yielded a CoMoCrSi coating with mechanical-metallurgical toughening effects at the interface, resulting in a high-toughness coating. Considering the ultra-thin wall and irregular cross-section characteristics of the irregularly shaped metal sealing ring, a double-sided hollow cathode segmented sputtering target was designed. The inner cavity of the target was parallel to the coating surface of the irregularly shaped metal sealing ring, forming a stable and independent hollow cathode discharge region, thus ensuring more uniform coating preparation. (See...) Figure 4 . Summary of the Invention

[0007] In view of the above situation, the present invention proposes a method for preparing a toughened CoMoCrSi coating on the surface of a thin-walled irregular metal sealing ring.

[0008] This invention discloses a toughened CoMoCrSi coating for a thin-walled, irregularly shaped metal sealing ring, utilizing a double-layer glow discharge plasma surface metallurgy technique. Using a CoMoCrSi alloy as the target material and a nickel-based high-temperature alloy thin-walled, irregularly shaped metal sealing ring as the workpiece, the coating is grown in three steps by controlling the workpiece surface temperature. The first step is a surface geometry reconstruction process: controlling the current density to regulate the micro-regional plastic deformation of the metal sealing ring surface, achieving a gradient change in roughness from the boundary to the center through edge effects. The second step is a mechanical-metallurgical bonding process: the hollow cathode effect causes remelting of the protruding positions in the plastic deformation region, accelerating the diffusion of target elements to achieve interfacial mechanical-metallurgical bonding. The third step is a deposition process: forming a surface-toughened CoMoCrSi coating with a gradient structure. The specific steps are as follows: Step 1: Surface geometry reconstruction process Use 400-2000# SiC sandpaper to grind and polish the target material to a mirror finish. Use a magnetic polisher to polish the workpiece for 5-20 minutes. Wipe with anhydrous ethanol and then ultrasonically clean for 15 minutes. Air dry for later use. The furnace chamber and tooling structure of the double-layer glow discharge plasma surface metallurgy equipment are wiped with anhydrous ethanol before installation, and the workpiece and target are placed there; the target is connected to the source power supply, the workpiece is connected to the cathode power supply, and the distance between the two electrodes of the workpiece and the target is 8~20mm. The vacuum level inside the furnace of the double-layer glow discharge plasma surface metallurgy equipment is controlled at 6×10⁻⁶ using a vacuum system. -4 When the pressure is below Pa, the argon gas flow rate is 15 sccm, the gas pressure inside the furnace is controlled at 20~50 Pa, and the power supply of the double-layer glow plasma surface metallurgy equipment is started. The surface temperature of the workpiece was measured using an infrared thermometer; during the micro-area plastic deformation process, the cathode power supply was increased separately, with the voltage adjusted by 15-20V every 1-3 minutes, the workpiece surface temperature was controlled at 350-500℃, and the current density was controlled at 5-15mA / cm². 2 Maintain for 10-30 minutes, and control the surface roughening process by using the current density to react with the instantaneous state of particle bombardment. Step 2: Mechanical-Metallurgical Integration Process Increase the source power supply separately, adjusting the voltage by 15-20V every 1-3 minutes, and controlling the current density at 40-60mA / cm². 2 Maintain for 10-30 minutes, and remelt the protruding positions in the plastic deformation area through the hollow cathode effect, thereby accelerating the diffusion of target elements and achieving interfacial mechanical-metallurgical bonding. Step 3: Deposition process The surface temperature of the workpiece is controlled at 750~850℃, the gas pressure inside the furnace is 20~50Pa, and the holding time is 2~5h. After the deposition process is completed, the source voltage is reduced to 0V first and then the cathode voltage is reduced. The voltage reduction rate is controlled at 10~15V / min to obtain a CoMoCrSi coating with mechanical-metallurgical toughening effect at the interface.

[0009] The chemical composition of the target material is as follows (by mass percentage): Mo: 15%~20%, Cr: 10%~15%, Si: 5.0%~10.0%, impurities: ≤ 1.0%, Co: balance. The target material adopts an upper and lower segmented structure design, and the shape of the target material is parallel to the main sealing surface of the workpiece, which facilitates the installation and adjustment of the distance between the workpiece and the target material.

[0010] The method of placing the workpiece and the target material adopts a multi-layer structure design, stacking the target material and workpiece assembly in 6 to 12 layers in the longitudinal direction to improve production efficiency.

[0011] The roughness gradient change from the boundary to the center is characterized by high roughness in the edge region and low roughness in the center region.

[0012] The beneficial effects of the present invention are as follows: 1. The target material of the present invention adopts a segmented structure, which facilitates the multi-layer installation of metal sealing rings and is suitable for simultaneous deposition of multiple workpieces; for irregular cross-sections, the hollow cathode effect is utilized to improve the coating sputtering efficiency.

[0013] 2. During the plasma surface geometry reconstruction process, the edge effect of plasma is used to construct a gradient surface roughness from the edge position to the center position, which enhances the mechanical interlocking ability of the coating. Micro-region plastic deformation is achieved by controlling the current density. The hollow cathode effect is applied to accelerate the diffusion rate of particles into the substrate, so that the coating and the substrate form a metallurgical bond, which increases the coating adhesion. The mechanical interlocking depth is 2~6μm, and the metallurgical diffusion layer is 1~5μm. The geometry reconstruction of the metal sealing ring surface and the preparation of the CoMoCrSi coating are both carried out in an inert gas protection environment to avoid corrosion and deterioration of the interfacial adhesion by impurities such as oxygen. A stable and uniform plasma heating zone is formed on the workpiece surface to eliminate the deformation caused by thermal stress during the deposition process.

[0014] 3. In view of the problems of rough operation and difficulty in tooling and fixture design and cooling gas distribution in existing thermal spraying technology, this invention proposes a method for preparing a metal surface coating that can improve the coating quality and is less likely to introduce impurities when applying a coating to irregular workpieces.

[0015] 4. The coating of this invention has strong toughness, simple assembly process, simple process, high production efficiency, low processing cost, good economic benefits, and is suitable for batch processing. Attached Figure Description

[0016] Figure 1 : Schematic diagram of the cross-section of the thin-walled C-shaped, W-shaped, U-shaped and Ω-shaped metal sealing rings involved in the coating of this invention by rolling; Figure 2 : Flowchart of the preparation process of the CoMoCrSi coating of this invention; In the diagram: 1. Working carrier gas; 2. Contact thermocouple; 3. Temperature display; 4. Source electrode rod; 5. Cathode electrode rod; 6. Connecting wire; 7. Surface infrared thermometer for the part; 8. Surface infrared thermometer for the target material; 9. Double-layer glow discharge region; 10. Observation window; 11. Vacuum system; 12. Source power supply; 13. Cathode power supply; Figure 3 The sputtering yields of pure Co, pure Mo, pure Cr, and pure Si targets in the CoMoCrSi alloy of this invention at 750°C, 800°C, and 850°C. In the diagram: 1. Co; 2. Mo; 3. Cr; 4. Si. Figure 4 : A schematic diagram of the thin-walled W-shaped metal sealing ring and CoMoCrSi alloy target material assembled in the furnace according to the present invention; In the diagram: 01, opening width; 02, slope; 03, interpole spacing; 04, depth; 05, upper segmented target; 06, lower segmented target; Figure 5 : A schematic diagram of the assembly and superposition of multiple thin-walled W-shaped metal sealing rings and CoMoCrSi alloy target material according to the present invention; Figure 6 The micro-region plastic deformation morphology of the workpiece surface according to the present invention; Figure 7a The mechanical interlocking cross-sectional morphology of the coating of this invention; Figure 7b : Enlarged view of the mechanical interlocking of the coating of this invention; Figure 7c The distribution of interface elements in the coating of this invention; In the diagram: A, deposited layer; B, metallurgical diffusion layer; C, nickel-based alloy matrix; Figure 8 : Test results of the interfacial adhesion of the CoMoCrSi coating in Example 1 of this invention; In the diagram: D, frictional force; E, coefficient of friction; F, acoustic signal; Figure 9a The roughness of the CoMoCrSi coating on the main sealing surface of this invention; In the diagram: a) left edge region; b) center region; c) right edge region; Figure 9b Surface morphology of the CoMoCrSi coating on the main sealing surface of this invention; Figure 10 : Test results of the interfacial adhesion of the CoMoCrSi coating in Example 2 of this invention; In the diagram: d, frictional force; e, coefficient of friction; f, acoustic signal. Detailed Implementation

[0017] Example 1 A toughened CoMoCrSi coating was prepared on the surface of a thin-walled W-shaped metal sealing ring using a double-layer glow discharge plasma surface metallurgy technique. The mass fractions of Co, Mo, Cr, and Si in the segmented target were 65%, 20%, 15%, and 5%, respectively. The coating-workpiece interface improved the coating / workpiece adhesion through a combined mechanical-metallurgical interaction, with a mechanical interlocking depth of 2–3 μm and a metallurgical diffusion depth of 2–3 μm. The edge effect was used to geometrically reconstruct the surface of the metal sealing ring, achieving a gradient change in roughness from the boundary to the center. The roughness was high in the edge region and low in the center region. The roughness of the main sealing surface was < Ra 3.2. The coating deposition thickness was 10–20 μm, and the interfacial adhesion force measured by the scratch method was > 70 N.

[0018] The preparation process includes the following steps: Step 1: Surface geometry reconstruction process The CoMoCrSi segmented alloy target was polished step by step using SiC sandpaper of 400-2000#, and then polished to a mirror finish using W5 diamond polishing paste. The metal sealing ring workpiece was polished using a magnetic polishing machine for 15 minutes to ensure good adhesion of the coating. After wiping with anhydrous ethanol, it was ultrasonically cleaned for 15 minutes and then air-dried for later use. The furnace chamber and tooling structure of the double-layer glow discharge plasma surface metallurgy equipment were wiped with anhydrous ethanol before installation. The workpiece and target were then placed. The CoMoCrSi alloy target was connected to the source power supply, and the metal sealing ring workpiece was connected to the cathode power supply. The electrode spacing between the workpiece and the target was 20mm. Six layers were stacked within the same spatial range. The stacking effect is shown in the diagram below. Figure 5 As shown; The vacuum level inside the furnace of the double-layer glow discharge plasma surface metallurgy equipment is controlled at 6×10⁻⁶ using a vacuum system. -4 Pa, argon gas is introduced, the argon gas flow rate is set to 15 sccm, the gas pressure in the furnace is controlled to 30 Pa, and the power supply of the double-layer glow plasma surface metallurgy equipment is started. The surface temperature of the workpiece is measured using an infrared thermometer; During the surface micro-area plastic deformation process, the cathode power supply is increased separately, with the voltage adjusted by 20V every 3 minutes. The surface temperature of the metal sealing ring workpiece is controlled at 425℃, and the current density is controlled at 10mA / cm². 2 Maintain for 15 minutes, and perform geometric reconstruction of the metal sealing ring surface through edge effect, see [link / reference]. Figure 6 ; Step 2: Mechanical-Metallurgical Integration Process Increase the source power supply separately, adjust the voltage by 15V every 2 minutes, and control the current density at 45mA / cm². 2Maintain for 10 minutes to allow metallurgical diffusion of the CoMoCrSi coating at the micro-region plastic deformation interface through the hollow cathode effect between the source and cathode. Step 3: Deposition process The surface temperature of the workpiece was controlled at 800℃, the gas pressure inside the furnace was 30Pa, and the holding time was 180min to form a CoMoCrSi deposition layer. After the deposition process is completed, the source voltage is reduced to 0V first, and then the cathode voltage is reduced. The voltage reduction rate is controlled at 15V / min. After cooling in the furnace for 300min, the workpiece is taken out to obtain a toughened CoMoCrSi coated workpiece.

[0019] The mechanical interlocking depth between the coating and the workpiece is 2.5 μm, the metallurgical diffusion depth is 2.8 μm, and the deposition layer thickness is 13.1 μm. (See attached image.) Figures 7a-7c The bonding force between the CoMoCrSi coating and the W-shaped metal sealing ring reached 76N. The mechanical interlocking structure improved the adhesion between the coating and the substrate. Figure 8 The surface roughness is gradient-varying from the edge to the center using the edge effect of plasma. The roughness of the main sealing surface is Ra 0.127, and the roughnesses of the edge sealing surfaces are Ra 0.303 and Ra 0.289, respectively. (See...) Figures 9a-9b .

[0020] Example 2 A toughened CoMoCrSi coating was prepared on the surface of a thin-walled C-shaped metal sealing ring using a double-layer glow discharge plasma surface metallurgy technique. The mass fractions of Co, Mo, Cr, and Si in the segmented target were 70%, 18%, 15%, and 7%, respectively. The coating-workpiece interface improved the coating / workpiece adhesion through a combination of mechanical and metallurgical bonding. The mechanical interlocking depth of the coating-workpiece interface was 3–5 μm, and the metallurgical diffusion depth was 2–5 μm. The edge effect was used to geometrically reconstruct the surface of the metal sealing ring, achieving a gradient change in roughness from the boundary to the center. The roughness of the edge region was high, and the roughness of the center region was low. The roughness of the main sealing surface was < Ra 3.2. The coating deposition thickness was 20–30 μm, and the interfacial adhesion force measured by the scratch method was > 80 N.

[0021] The preparation method includes the following steps: Step 1: Surface geometry reconstruction process The CoMoCrSi segmented alloy target was polished step by step using SiC sandpaper of 400-2000#, and then polished to a mirror finish using W5 diamond polishing paste. The metal sealing ring workpiece was polished using a magnetic polishing machine for 15 minutes to ensure good adhesion of the coating. After wiping with anhydrous ethanol, it was ultrasonically cleaned for 15 minutes and then air-dried for later use. After wiping the furnace and tooling structure of the double-layer glow plasma surface metallurgy equipment with anhydrous ethanol, the equipment is installed, and the workpiece and target are placed. The CoMoCrSi alloy target is connected to the source power supply, and the metal sealing ring workpiece is connected to the cathode power supply. Since the coating surfaces of the C-type metal sealing ring and the W-type metal sealing ring are different, the electrode spacing is adjusted to 10mm. Similarly, 9 layers are stacked in the space. The vacuum level inside the furnace of the double-layer glow discharge plasma surface metallurgy equipment is controlled at 6×10⁻⁶ using a vacuum system. -4 Pa, argon gas is introduced, the argon gas flow rate is set to 15 sccm, the gas pressure in the furnace is controlled to 40 Pa, and the power supply of the double-layer glow plasma surface metallurgy equipment is started. The surface temperature of the workpiece is measured using an infrared thermometer; During the surface micro-area plastic deformation process, the cathode power supply is increased separately, with the voltage adjusted by 20V every 3 minutes. The surface temperature of the metal sealing ring workpiece is controlled at 480℃, and the current density is controlled at 15mA / cm². 2 Heat preservation for 25 minutes, and micro-area plastic deformation of the surface of the metal sealing ring is performed through edge effect; Step 2: Mechanical-Metallurgical Integration Process Increase the source power supply separately, adjust the voltage by 15V every 2 minutes, and control the current density at 55mA / cm². 2 Maintain for 30 minutes to allow metallurgical diffusion of the CoMoCrSi coating at the micro-region plastic deformation interface through the hollow cathode effect between the source and cathode. Step 3: Deposition process The surface temperature of the workpiece was controlled at 850℃, the gas pressure inside the furnace was 40Pa, and the holding time was 300min to form a CoMoCrSi deposition layer. After the deposition process is completed, the source voltage is reduced to 0 V first, and then the cathode voltage is reduced. The voltage reduction rate is controlled at 15 V / min. After cooling in the furnace for 300 min, the workpiece is taken out to obtain a toughened CoMoCrSi coated workpiece.

[0022] Mechanical interlocking occurs between the coating and the workpiece, resulting in geometric reconstruction of the metal sealing ring surface. The mechanical interlocking depth between the coating and the workpiece is 3.5 μm, the metallurgical diffusion depth is 3.6 μm, the deposition layer thickness is 23.7 μm, and the bonding force between the CoMoCrSi coating and the C-shaped metal sealing ring reaches 82 N (see...). Figure 10 The mechanical interlocking structure improves the bonding force between the coating and the substrate, and utilizes the edge effect of plasma to create a gradient surface roughness from the edge position to the center position, where the roughness of the edge region is high and the roughness of the center region is low.

Claims

1. A thin-walled contoured metal seal ring surface toughened CoMoCrSi coating, characterized by: The coating is obtained by three steps through double-layer glow plasma surface metallurgy technology, taking CoMoCrSi alloy as target material and nickel-based high-temperature alloy thin-wall special-shaped metal sealing ring as workpiece, and by controlling the surface temperature of the workpiece; the first step is surface geometric reconstruction process: the plastic deformation of the surface micro area of the metal sealing ring is regulated by controlling the current density, and the gradient change of roughness from the boundary to the center is realized by means of edge effect; the second step is mechanical-metallurgical combination process: the remelting of the protruding position of the plastic deformation area is caused by hollow cathode effect, and the interface mechanical-metallurgical combination is realized by accelerating the diffusion of target material elements; the third step is deposition process: the surface toughening CoMoCrSi coating with gradient structure is formed; The specific steps are as follows: Step 1: surface geometric reconstruction process The target material is polished and polished into a mirror surface by using 400-2000# SiC sandpaper step by step, the workpiece is polished by using a magnetic polishing machine, the polishing time is 5-20 min, and then the workpiece is ultrasonically cleaned for 15 min after being wiped with anhydrous ethanol, and then dried in the air for standby; The furnace and tool structure of the double-layer glow plasma surface metallurgy equipment are wiped with anhydrous ethanol and then installed, and the workpiece and the target material are placed; wherein the target material is connected with the source power supply, the workpiece is connected with the cathode power supply, and the distance between the two sides of the workpiece and the target material is 8-20 mm; The vacuum degree in the furnace of the double-layer glow plasma surface metallurgy equipment is controlled at 6x10 -4 When the pressure in the furnace is controlled at 20-50 Pa, the argon gas flow is 15 sccm, and the power supply of the double-layer glow plasma surface metallurgy equipment is started. The surface temperature of the workpiece is measured by an infrared temperature detector; the cathode power supply is separately raised during the plastic deformation process of the surface micro-area, the voltage is adjusted by 15-20 V every 1-3 min, the surface temperature of the workpiece is controlled at 350-500 DEG C, the current density is controlled at 5-15 mA / cm 2 , and maintained for 10-30 min, so that the surface roughening process is controlled in the state of instantaneous particle bombardment by current density. Step 2: mechanical-metallurgical combination process The voltage of the source power supply is raised alone, and the voltage is adjusted by 15-20 V every 1-3 min, and the current density is controlled at 40-60 mA / cm 2 The interface mechanical-metallurgical combination is realized by remelting the convex position of the plastic deformation area caused by the hollow cathode effect and accelerating the diffusion of the target material elements, and is maintained for 10-30 min. Step 3: deposition process The surface temperature of the workpiece is controlled to be 750-850 DEG C, the gas pressure in the furnace is 20-50 Pa, and the holding time is 2-5 h; after the deposition process is completed, the source voltage is first reduced to 0 V and then the cathode voltage is reduced, and the voltage reduction rate is controlled to be 10-15 V / min, so that the CoMoCrSi coating with mechanical-metallurgical toughening effect is obtained.

2. A surface toughened CoMoCrSi coating for thin-walled profiled metal seal rings according to claim 1, characterized in that: The chemical composition of the target material is as follows: Mo: 15%-20%, Cr: 10%-15%, Si: 5.0%-10.0%, impurities: ≤1.0%, and Co: the balance; the target material adopts upper and lower split structure design, and the shape of the target material is parallel to the main sealing surface of the workpiece, so that the distance between the workpiece and the target material can be easily installed and adjusted.

3. The surface toughened CoMoCrSi coating for thin-walled profiled metal seal rings according to claim 1, characterized in that: The workpiece and the target material are placed in a multi-layer structure design, and the assembly of the target material and the workpiece is stacked in the longitudinal range for 6-12 layers, so that the production efficiency is improved.

4. The surface toughened CoMoCrSi coating for thin-walled profiled metal seal rings according to claim 1, characterized in that: The gradient change of roughness from the boundary to the center is that the roughness of the edge area is high and the roughness of the center area is low.

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