Ball valve ball and its supersonic spraying process

Abstract

The application relates to the technical field of ball valves, and provides a ball valve ball body and an ultrasonic spraying process thereof. The process comprises the following steps: pre-processing a ball body base body to form an outer spherical surface, a through-flow hole and a valve rod connecting part; determining an annular sealing band area for sealing cooperation with a valve seat on the outer spherical surface; adopting ultrasonic spraying composite powder on the annular sealing band area to form a composite coating; and performing grinding treatment and fine grinding polishing on the composite coating to make the composite coating form a sealing working surface, thereby obtaining the ball valve ball body. The composite coating is formed by adopting ultrasonic spraying composite powder on the annular sealing band area of the ball body base body, the composite coating forms a hard bearing area and a discrete friction-reducing micro area on the sealing working surface, the ball valve ball body can bear the valve seat sealing specific pressure and medium scouring during opening and closing, the opening and closing friction and the sealing surface scratch risk are reduced, the wear resistance, scratch resistance and sealing stability of the sealing working surface of the ball valve ball body are improved, and the service life of the ball valve is prolonged.

Description

Technical Field

[0001] This invention relates to the field of ball valve technology, and more specifically, to a ball valve ball and its supersonic spraying process. Background Technology

[0002] A ball valve is a type of valve that controls the flow of media or regulates flow by rotating a ball around the valve stem axis. The outer spherical surface of the ball forms a sealing fit with the valve seat. During opening and closing, the ball's sealing surface repeatedly contacts, rubs against, and separates from the valve seat. In the closed state, the ball's sealing surface also needs to withstand the sealing pressure applied by the valve seat and the pressure of the pipeline medium. Therefore, the surface quality, wear resistance, and anti-scratch properties of the ball's sealing surface directly affect the ball valve's opening and closing torque, sealing reliability, and service life.

[0003] For ball valves used under high pressure, with particulate media, corrosive media, or in frequent opening and closing conditions, the ball sealing surface is easily subjected to the combined effects of media erosion, particle scratches, and repeated friction from the valve seat, leading to problems such as wear, scoring, abrasion, and localized peeling. When the ball sealing surface is damaged, the fit between the ball and the valve seat is disrupted, easily resulting in increased valve opening and closing torque, increased sealing leakage, and in severe cases, ball valve seal failure.

[0004] In existing technologies, to improve the wear resistance of the ball in a ball valve, a hard coating, weld overlay, or spray coating is typically formed in the ball's sealing area. For example, hard chrome plating, nickel-based alloy layers, tungsten carbide coatings, or chromium carbide coatings are used to improve the hardness and wear resistance of the ball's sealing surface. However, simply increasing the hardness of the sealing surface cannot completely solve the problem of friction and scratching during the opening and closing of the ball valve. Although hard coatings have high wear resistance, their surface friction coefficient is high, and under conditions of high seat sealing pressure or frequent opening and closing, scratches, seizing, or abnormal wear between the sealing surfaces may still occur.

[0005] In addition, some hard coatings also have problems such as insufficient coating toughness, high risk of local peeling, large surface roughness after spraying, and high difficulty in subsequent grinding. If the bonding stability between the coating and the ball substrate is insufficient, the ball valve is prone to coating cracking or peeling during long-term pressure, erosion and friction. If the coating surface has insufficient friction reduction capacity, the ball is prone to generating large frictional resistance during opening and closing, and aggravating the mutual damage between the valve seat and the ball sealing working surface.

[0006] Therefore, how to form a composite surface structure on the sealing working surface of the ball valve ball that has both high hardness and wear resistance, while reducing the risk of opening and closing friction and sealing surface scratches, is a technical problem that urgently needs to be solved in the field of ball valve ball processing. Summary of the Invention

[0007] This invention aims to provide a ball valve ball and its supersonic spraying process. By using supersonic spraying of composite powder to form a composite coating in the annular sealing zone area of ​​the ball substrate, the composite coating forms a hard bearing area and discrete friction-reducing micro-areas on the sealing working surface. This enables the ball valve ball to withstand the valve seat sealing pressure and media erosion during opening and closing, reduces the risk of opening and closing friction and sealing surface abrasion, improves the wear resistance, abrasion resistance and sealing stability of the ball valve ball's sealing working surface, and extends the service life of the ball valve.

[0008] To address the above problems, this invention provides a supersonic spraying process for a ball valve ball, comprising the following steps: S1. Pre-process the spherical base to form the outer spherical surface, flow passage, and valve stem connection; S2. Determine the annular sealing zone area on the outer spherical surface for sealing with the valve seat; S3. Apply composite powder using supersonic spraying in the annular sealing zone area to form a composite coating. S4. Grind and polish the composite coating to form a sealing working surface, thus obtaining the ball valve ball. The composite powder includes hard carbide powder, metal-bonded powder, and self-lubricating microparticles; the composite coating includes a hard carbide carrier phase, a metal-bonded phase, and a self-lubricating microphase. After grinding and fine polishing, at least a portion of the self-lubricating microphase located near the surface of the composite coating is exposed on the sealing working surface. The sealing working surface includes a hard carrier area and a discrete friction-reducing micro-area. The discrete friction-reducing micro-area includes the self-lubricating microphase exposed on the sealing working surface; the hard carrier area includes the hard carbide carrier phase and the metal-bonded phase.

[0009] In the above technical solution, the self-lubricating microparticles include a self-lubricating core layer and a metal shell layer covering at least part of the surface of the self-lubricating core layer. During the grinding and polishing process, the self-lubricating microphase located near the surface of the composite coating is locally truncated, so that the self-lubricating core layer forms a discrete exposed area on the sealed working surface. The self-lubricating core layer includes at least one of CaF2 and BaF2; the metal shell layer includes at least one of Ni, Co, Ni-P, Ni-Co, NiCr, CoCr, NiCrMo, and CoNiCr.

[0010] In the above technical solution, the hard carbide powder includes at least one of WC, Cr3C2, TiC, NbC, and VC; and / or the metal-bonded powder includes at least one of CoCr, NiCr, NiCrMo, CoNiCr, FeCoNiCr, and FeCoNiCrMo.

[0011] In the above technical solution, the preparation method of composite powder includes the following steps: S31, mixing hard carbide powder and metal-bonded powder to obtain hard base powder; S32, adding self-lubricating microparticles to hard base powder, and obtaining composite powder through low-shear mixing and spray granulation.

[0012] The above technical solution also includes S21, which involves pre-treatment of the annular sealing strip area, including degreasing and cleaning, sandblasting and roughening, and surface cleaning.

[0013] In the above technical solution, self-lubricating microparticles account for 0.5-8% of the total mass of the composite powder.

[0014] In the above technical solution, the D50 of the hard carbide powder is 10~45μm; the D50 of the self-lubricating microparticles is 5~15μm; and the thickness of the composite coating is 100~400μm.

[0015] In the above technical solution, the discrete friction-reducing micro-regions are separated by a hard carbide carrier phase and / or a metal bonding phase, and the discrete friction-reducing micro-regions account for 0.3~6% of the sealing working surface area.

[0016] In the above technical solution, in S3, supersonic spraying includes supersonic flame spraying or supersonic air-fuel spraying.

[0017] The present invention also provides a ball valve ball, which is manufactured by any of the supersonic spraying processes described above. The ball valve ball includes a ball substrate and a composite coating formed in the annular sealing zone region of the ball substrate. The sealing working surface formed by the composite coating includes a hard bearing area and a discrete friction-reducing micro-area. The discrete friction-reducing micro-area includes a self-lubricating micro-phase exposed on the sealing working surface. The hard bearing area includes a hard carbide bearing phase and a metal bonding phase.

[0018] Beneficial effects (1) The present invention forms a composite coating in the annular sealing zone area of ​​the sphere substrate, so that the composite coating corresponds to the actual sealing contact area of ​​the sphere, which can improve the wear resistance and scratch resistance of the key load-bearing area and reduce unnecessary spraying and grinding in the non-sealing area; (2) The composite coating of the present invention includes a hard carbide support phase, a metal bonding phase and a self-lubricating micro phase, wherein the hard carbide support phase is used to bear the valve seat sealing pressure and the scouring wear of the medium, the metal bonding phase is used to improve the coating toughness and bonding stability, and the self-lubricating micro phase is used to reduce the frictional resistance and the risk of scratching of the sealing surface during the opening and closing process, so that the sealing working surface has both wear-resistant bearing capacity and friction-reducing and scratch-resistant performance. (3) By distributing the self-lubricating microphase in the composite coating and exposing the self-lubricating microphase on the sealing working surface after grinding and polishing, the present invention can form a local friction reduction effect in the contact area between the ball and the valve seat, while avoiding the continuous self-lubricating phase leading to a decrease in the bearing capacity of the sealing working surface or the formation of leakage channels; (4) When the self-lubricating microparticles adopt a coating structure composed of a self-lubricating core layer and a metal shell layer, the metal shell layer can reduce the melting migration, scattering, agglomeration or interface debonding of the self-lubricating core layer during the supersonic spraying process, and improve the bonding stability between the self-lubricating microparticles and the metal bonding phase; in the subsequent grinding and polishing process, the self-lubricating core layer can form a discrete exposed area on the sealing working surface, thereby further improving the friction reduction and anti-scratch effect of the sealing working surface. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0020] Unless otherwise specified, the materials, equipment and process conditions used in this invention can all be conventional materials, equipment and process conditions in the field.

[0021] For ball valves used under high pressure, with particulate media, or under frequent opening and closing conditions, the ball sealing surface is easily subjected to media erosion, particle scratches, and repeated friction from the valve seat, resulting in wear, scratches, abrasions, or localized peeling. This leads to increased opening and closing torque, decreased sealing performance, or even sealing failure. Existing technologies typically improve the hardness and wear resistance of the ball sealing surface through hard chrome plating, nickel-based alloy layers, tungsten carbide coatings, or chromium carbide coatings. However, simply increasing hardness is insufficient to simultaneously achieve low friction and anti-scratch performance, and abnormal wear of the sealing pair may still occur under high sealing pressure or frequent opening and closing conditions.

[0022] Based on the aforementioned technical problems, this embodiment provides a supersonic spraying process for a ball valve ball. By applying a composite powder to the annular sealing zone of the ball substrate using supersonic spraying to form a composite coating, the composite coating creates a hard load-bearing zone and discrete friction-reducing micro-zones on the sealing working surface. This allows the ball valve ball to withstand the valve seat sealing pressure and media erosion during opening and closing, reducing opening and closing friction and the risk of abrasion on the sealing surface. This improves the wear resistance, abrasion resistance, and sealing stability of the ball valve ball's sealing working surface, extending the service life of the ball valve. The supersonic spraying process includes the following steps: S1. Pre-process the spherical base to form the outer spherical surface, flow passage, and valve stem connection; S2. Determine the annular sealing zone area on the outer spherical surface for sealing with the valve seat; S3. Apply composite powder using supersonic spraying in the annular sealing zone area to form a composite coating. S4. Grind and polish the composite coating to form a sealing working surface, thus obtaining the ball valve ball.

[0023] Specifically, in S1, the ball base can be made of stainless steel, alloy steel, carbon steel, or other metal materials suitable for ball valve balls; pre-processing includes blanking, forging or casting, rough turning, semi-finish turning, outer spherical surface machining, drilling or boring of the flow hole, milling or inserting of the valve stem connection, deburring, cleaning, and necessary stress relief treatment. Through the above pre-processing, the ball base is pre-formed into a basic geometry close to the final product, and a stable processing benchmark is provided for subsequent determination of the annular sealing zone area, implementation of localized supersonic spraying, and grinding and polishing.

[0024] In S2, an annular sealing zone area for sealing with the valve seat is defined on the outer spherical surface. The annular sealing zone area can be determined based on the actual contact trajectory between the valve seat and the outer spherical surface of the ball, the width of the valve seat sealing surface, the opening angle of the ball valve, and the sealing specific pressure distribution.

[0025] Preferably, the width of the annular sealing band area is greater than the actual contact band width of the valve seat, so that even after ball valve assembly errors, opening and closing offsets, or wear of the sealing pair, the valve seat can still maintain effective sealing contact with the composite coating.

[0026] Furthermore, the annular sealing zone includes the main sealing area corresponding to the actual contact area of ​​the valve seat and the transition area located on both sides of the main sealing area. After grinding, the transition area smoothly transitions with the adjacent outer spherical surface to avoid abrupt steps at the edge of the composite coating.

[0027] The purpose of setting up the annular sealing zone is to concentrate the composite coating on the area where the ball and valve seat actually experience sealing contact and frictional wear, rather than indiscriminately spraying the entire outer surface of the ball. This allows the coating material and spraying energy to be concentrated on the critical sealing area, improving the wear resistance and scratch resistance of the sealing zone. It also reduces unnecessary coating deposition in non-sealing areas, decreasing subsequent grinding work and avoiding residual stress accumulation and ball size deviations caused by large-area spraying. During the opening and closing of the ball valve, the areas primarily subjected to valve seat sealing pressure, sliding friction, and media erosion are concentrated near the valve seat contact trajectory. Placing the composite coating in this annular sealing zone ensures that the reinforced layer corresponds to the actual load-bearing area, thereby improving coating utilization efficiency and sealing reliability.

[0028] Furthermore, between S2 and S3, S21 is included: pretreatment of the annular sealing strip area, which includes degreasing and cleaning, sandblasting roughening, and surface cleaning. In specific operations, organic solvents, alkaline cleaning solutions, or ultrasonic cleaning methods can be used to remove oil stains, cutting fluid residues, and impurities from the surface of the annular sealing strip area; then, alumina sand, brown corundum sand, or other sandblasting media can be used to roughen the annular sealing strip area; after sandblasting, residual dust and loose particles can be removed by compressed air blowing, anhydrous ethanol wiping, or plasma cleaning.

[0029] The above treatments improve the bonding stability between the composite coating and the spherical substrate. Degreasing and cleaning remove surface organic contaminants, preventing thermal decomposition during spraying and the formation of weak interfaces. Sandblasting roughens the surface, creating a micro-uneven structure in the annular sealing zone, enhancing the mechanical interlocking ability of the spherical substrate surface. Surface cleaning removes sandblasting residue, preventing inclusions from remaining at the coating-substrate interface. When supersonic spray particles impact the roughened metal surface at high speed, molten or semi-molten particles embed themselves between the micro-pits and rough peaks and valleys of the substrate surface, forming a mechanically interlocking structure upon cooling. Simultaneously, the metal bonding phase can form a tighter interfacial contact in localized areas, thereby reducing the risk of cracking or peeling of the coating under opening and closing friction, media erosion, and sealing pressure.

[0030] Specifically, in S3, a composite powder is applied using supersonic spraying in the annular sealing zone area to form a composite coating. Supersonic spraying can be supersonic flame spraying or supersonic air-fuel spraying. During supersonic spraying, the composite powder is heated and accelerated in a high-speed flame or high-speed hot gas stream, and then impacts the surface of the annular sealing zone area at high speed. The powder particles spread, deform, stack, and rapidly solidify, ultimately forming a dense composite coating.

[0031] Through the above treatment, a composite surface layer with wear-resistant load-bearing capacity and friction-reducing and scratch-resistant capabilities is formed in the spherical sealing working area. Compared with ordinary welding or low-speed thermal spraying, supersonic spraying has the characteristics of high particle flight speed, low coating porosity, high bonding strength, and relatively controllable heat input, which can reduce the thermal deformation of the spherical substrate and facilitate the formation of a dense and uniform sealing band coating. After high-speed particles impact the substrate, they form a layered stacked structure. Hard carbide particles constitute the main load-bearing skeleton, the metallic bonding phase fills the gaps between the hard particles and connects the hard phases, and the self-lubricating microphase is dispersed and embedded in the hard load-bearing structure, so that the composite coating simultaneously possesses hard load-bearing, tough bonding, and local friction-reducing functions.

[0032] Furthermore, supersonic spraying includes supersonic flame spraying or supersonic air-fuel spraying. Supersonic flame spraying is characterized by high flame velocity, high deposition efficiency, and good coating density, making it suitable for forming high wear-resistant composite coatings such as WC-based and Cr3C2-based coatings. Supersonic air-fuel spraying has a relatively low flame temperature and a high particle velocity, which can reduce the risk of decarburization and oxidation of some carbides, as well as thermal damage to self-lubricating components.

[0033] Preferably, the composite powder comprises hard carbide powder, metal-bonded powder, and self-lubricating microparticles. The hard carbide powder forms a hard carbide load-bearing phase in the composite coating to improve the hardness, wear resistance, and resistance to media erosion of the sealing working surface. The metal-bonded powder forms a metal-bonded phase in the composite coating to improve the coating's toughness, bonding strength, and anti-stripping ability. The self-lubricating microparticles form a self-lubricating microphase in the composite coating to reduce the risk of opening and closing friction and abrasion between the ball and the valve seat. These three components form a synergistic structure in the composite coating, making it not just a single hard wear-resistant layer, but a composite functional layer that combines wear resistance, load bearing, friction reduction, and anti-abrasion properties.

[0034] The core-shell structure of self-lubricating microparticles reduces the risk of burn-off, oxidation, decomposition, or dispersion of the self-lubricating core layer during high-temperature, high-speed spraying, thus improving the retention rate of the self-lubricating component in the composite coating. Simultaneously, the metal shell exhibits good compatibility with the metal bonding phase, reducing the risk of porosity, detachment, or interfacial cracking between the self-lubricating particles and the coating substrate due to poor wettability. Furthermore, the metal shell undergoes plastic deformation during spraying impact and participates in interlayer bonding, allowing the self-lubricating microparticles to be more stably embedded between the hard carbide carrier phase and the metal bonding phase. Uncoated self-lubricating powders typically suffer from large density variations, insufficient thermal stability, or weak interfacial bonding, making them prone to burn-off, agglomeration, or detachment from the coating during spraying. The metal shell acts as a transitional bonding interface outside the self-lubricating core layer, enabling the self-lubricating microparticles to be retained in the coating while also being exposed after subsequent grinding to exert a friction-reducing effect.

[0035] Furthermore, the self-lubricating microparticles include a self-lubricating core layer and a metal shell coating at least a portion of the surface of the self-lubricating core layer; wherein the self-lubricating core layer includes at least one of CaF2 and BaF2; and the metal shell includes at least one of Ni, Co, Ni-P, Ni-Co, NiCr, CoCr, NiCrMo, and CoNiCr. The self-lubricating core layer provides low-friction or solid lubrication, and the metal shell improves the compatibility between the self-lubricating core layer and the metal bonding phase, and protects the self-lubricating core layer during supersonic spraying. The metal shell can be formed by chemical plating, mechanical coating, spray granulation composite coating, or physical vapor deposition.

[0036] Preferably, the D50 of the hard carbide powder is 10~45μm. Controlling the particle size of the hard carbide powder within this range is beneficial for ensuring the heating, acceleration, and deposition efficiency of the powder during supersonic spraying, and for enabling the coating to form a continuous and stable hard load-bearing skeleton. The particle size of the self-lubricating microparticles is controlled within 5~15μm, which is beneficial for the self-lubricating microphase to exist in the composite coating as dots, islands, or short strips, avoiding the formation of large-sized soft defects or continuous lubrication channels. The particle size of the self-lubricating microparticles is smaller than that of the hard carbide powder, allowing the self-lubricating microphase to embed between the hard carbide load-bearing phase and the metal bonding phase, thereby providing localized friction reduction without significantly weakening the coating's load-bearing capacity.

[0037] Preferably, the hard carbide powder includes at least one of WC, Cr3C2, TiC, NbC, and VC. WC has high hardness and excellent wear resistance, making it suitable for improving the wear resistance of the sealing working surface; Cr3C2 has good high-temperature oxidation resistance and corrosion resistance, making it suitable for corrosive media or high-temperature conditions; TiC, NbC, and VC can be used to improve the stability of the hard phase and scratch resistance of the composite coating. The metal-bonding powder includes at least one of CoCr, NiCr, NiCrMo, CoNiCr, FeCoNiCr, and FeCoNiCrMo. CoCr, NiCr, NiCrMo, and CoNiCr metal-bonding powders can form a tough bonding phase, improving the overall bonding strength and crack resistance of the coating; FeCoNiCr, FeCoNiCrMo, and other multi-element alloy powders can also improve the corrosion resistance and microstructure stability of the coating. The combined use of hard carbide powder and metal-bonding powder can avoid the brittle cracking problem caused by the hard phase alone, giving the composite coating better overall stability when subjected to sealing pressure and sliding friction.

[0038] Preferably, the self-lubricating microparticles account for 0.5-8% of the total mass of the composite powder. When the content of self-lubricating microparticles is less than 0.5%, the number of self-lubricating microphases formed in the composite coating is small, and the self-lubricating area exposed on the sealing working surface after grinding and polishing is insufficient, making it difficult to effectively reduce opening and closing friction. When the content of self-lubricating microparticles is higher than 8%, the self-lubricating microphases are prone to local enrichment in the coating, which may reduce the hardness, load-bearing capacity and compressive strength of the composite coating, or even form a continuous soft phase or weak interface, affecting the long-term stability of the sealing working surface.

[0039] Furthermore, the method for preparing the composite powder includes the following steps: S31. Hard carbide powder and metal-bonded powder are mixed to obtain hard base powder; S32. Self-lubricating microparticles are added to hard base powder, and the composite powder is obtained by low-shear mixing and spray granulation.

[0040] In S31, the hard carbide powder and the metal-bonded powder are first mixed to form a hard base powder. This facilitates the pre-uniform dispersion of the hard phase and the metal-bonded phase, enabling the hard carbide carrier phase in the subsequent composite coating to be effectively linked by the metal-bonded phase. If the hard carbide powder and the metal-bonded powder are not mixed uniformly, local enrichment of the hard phase or the metal phase may easily occur in the coating. The former may lead to coating brittleness, while the latter may lead to insufficient local wear resistance.

[0041] In S32, self-lubricating microparticles are added to the hard base powder, and low-shear mixing is used. This helps reduce the risk of shell breakage, core exposure, or particle breakage of the self-lubricating microparticles, especially core-shell self-lubricating microparticles, during the mixing process. Subsequently, spray granulation is used to form composite powder particles with a certain particle size, flowability, and compositional uniformity from the hard carbide powder, metal-bonded powder, and self-lubricating microparticles.

[0042] Spray granulation can include: mixing hard base powder, self-lubricating microparticles, temporary binder, and dispersion medium to form a slurry; spray drying the slurry; and sieving the spray-dried powder to obtain a composite powder suitable for supersonic spraying. Spray granulation can reduce stratification and segregation of powders with different densities during storage, transportation, and powder delivery, allowing each component to enter the spraying flame with the same composite powder particles, thereby improving the uniformity and dispersion stability of the self-lubricating microphase in the composite coating. There are differences in particle size, density, and morphology among hard carbide powder, self-lubricating microparticles, and metal-bonded powder. If only simple mechanical mixing is performed, segregation is easily generated during powder delivery, resulting in excessive or insufficient lubricating phase in certain areas of the coating. Spray granulation can fix each component in the composite particles, ensuring synchronous deposition of each component during spraying.

[0043] Preferably, the thickness of the composite coating is 100~400μm. When the thickness of the composite coating is less than 100μm, the effective thickness of the coating may be insufficient after subsequent grinding and fine polishing, which will affect the wear resistance life of the sealing working surface. When the thickness of the composite coating is greater than 400μm, the residual stress of the coating increases, which can easily cause cracking, warping or local peeling, and increase the difficulty of grinding.

[0044] In step S4, the composite coating undergoes grinding and fine polishing to form a sealing working surface, resulting in the ball valve ball. Grinding can include coarse grinding and fine grinding to remove peaks, spatter particles, and uneven areas from the surface of the sprayed composite coating, and to correct the spherical accuracy of the coating. Fine polishing further reduces the surface roughness of the sealing working surface to meet the requirements for sealing with the valve seat. Since the surface of the coating after supersonic spraying typically exhibits a certain degree of roughness and thickness fluctuation, without grinding and fine polishing, it is difficult to form a continuous and stable sealing contact between the ball and the valve seat. Grinding and fine polishing remove high points on the coating surface, allowing the hard carbide carrier phase, the metallic bonding phase, and the self-lubricating microphase to collectively form a smooth sealing working surface, thereby improving the sealing reliability of the ball valve in the closed state.

[0045] Preferably, after grinding and fine polishing, the self-lubricating microphase located on the sealing working surface is partially truncated, causing the self-lubricating core layer to form discrete friction-reducing micro-regions on the sealing working surface. Specifically, during the spraying process, the self-lubricating microparticles are stably embedded inside the composite coating through the metal shell; during subsequent grinding and fine polishing, the self-lubricating microparticles located near the surface of the coating are ground and truncated, and part of the metal shell is removed or opened, causing the internal self-lubricating core layer to be partially exposed on the sealing working surface. Thus, during the opening and closing of the ball valve, the exposed self-lubricating core layer can form a micro-region lubrication effect in the contact area between the ball and the valve seat, reducing the coefficient of friction and the opening and closing torque, and reducing scratches, seizing, and roughening between the sealing pairs. At the same time, because the discrete friction-reducing micro-regions are separated by hard load-bearing areas, the sealing working surface still maintains high hardness and load-bearing capacity, and will not soften or form leakage channels due to the continuity of the self-lubricating phase.

[0046] Furthermore, the sealing working surface includes a hard bearing area and discrete friction-reducing micro-regions. The discrete friction-reducing micro-regions include self-lubricating micro-phases exposed on the sealing working surface. The hard bearing area includes a hard carbide bearing phase and a metallic bonding phase, and adjacent discrete friction-reducing micro-regions are separated by the hard bearing area, so that the self-lubricating micro-phase exists as a local friction-reducing unit in the sealing working surface, while the hard carbide bearing phase and the metallic bonding phase still maintain a continuous or nearly continuous bearing structure. If the self-lubricating micro-phase is continuously distributed, the sealing working surface is prone to forming a soft continuous phase or a weak bonding channel, resulting in a decrease in bearing capacity, increased wear, or an increased risk of leakage. The discretely distributed self-lubricating micro-phase can provide local lubrication and friction transfer during the opening and closing of the sphere, while the surrounding hard carbide bearing phase bears the main sealing specific pressure and wear load, thereby achieving a synergy between wear-resistant bearing and friction reduction and anti-scratch.

[0047] Furthermore, the discrete friction-reducing micro-regions account for 0.3% to 6% of the sealing working surface area. When the area of ​​discrete friction-reducing micro-regions is less than 0.3%, the number of self-lubricating micro-phases exposed on the sealing working surface is insufficient, and the friction-reducing effect is not obvious. When the area of ​​discrete friction-reducing micro-regions is greater than 6%, the self-lubricating micro-phases are prone to form a local continuous distribution, which leads to a decrease in the load-bearing capacity of the sealing working surface and even the risk of leakage.

[0048] Preferably, the surface roughness of the sealing working surface is 0.03~0.08μm, which can reduce the leakage channels formed by the micro-peaks and valleys of the sealing surface and improve the sealing reliability between the ball and the valve seat; at the same time, it can reduce the scraping wear of the hard carbide bearing relative to the valve seat and make the discrete exposed self-lubricating core layer effectively participate in frictional contact, thereby reducing the opening and closing torque and improving the service life of the sealing surface.

[0049] This application also provides a ball valve ball, which is manufactured using any of the above-mentioned supersonic spraying processes. The reinforcement range is defined by an annular sealing zone, the coating interface bonding is improved through pretreatment, and a composite coating is formed by supersonic spraying, comprising a hard carbide carrier phase, a metallic bonding phase, and a self-lubricating microphase. Furthermore, grinding and fine polishing create discrete friction-reducing micro-zones on the sealing surface through the self-lubricating core layer. This results in the ball valve ball's sealing surface possessing high wear resistance, low friction and anti-scratch properties, and long-term sealing stability.

[0050] Example 1

[0051] This embodiment provides a ball valve ball and its supersonic spraying process. The supersonic spraying process includes the following steps: S1. Stainless steel is selected as the base material for the ball. The ball base is blanked, forged, rough turned, semi-finish turned and the outer spherical surface is machined to form the outer spherical surface. Then, the ball base is drilled and bored to form the flow hole, and the valve stem connection is milled to form the flow hole and the valve stem connection. S2. Based on the sealing contact trajectory between the valve seat and the outer spherical surface of the ball, determine the annular sealing zone area on the outer spherical surface for sealing cooperation with the valve seat; S21. Use alkaline cleaning solution to degrease and clean the annular sealing strip area, and then use alumina sand with a particle size of 80 mesh to roughen the surface of the annular sealing strip area. After sandblasting, use compressed air to blow and wipe with anhydrous ethanol to remove residual dust and loose particles. S3. Supersonic flame spraying of composite powder is used in the annular sealing zone area to form a composite coating. S4. The composite coating is coarsely ground with diamond abrasive with a particle size of 200 mesh, finely ground with diamond polishing paste with a particle size of 1000 mesh, and finally finely polished with diamond polishing paste with a particle size of 3μm. This makes the composite coating form a sealing working surface with a surface roughness Ra of 0.08μm. The self-lubricating microphase located near the surface of the composite coating is locally truncated, so that the CaF2 self-lubricating core layer forms a discrete friction-reducing micro-region on the sealing working surface, thus obtaining the ball valve ball. The composite powder comprises WC hard carbide powder with a D50 of 10 μm, CoCr metal-bonded powder with a D50 of 15 μm, and self-lubricating microparticles with a D50 of 5 μm, wherein the self-lubricating microparticles account for 0.5% of the total mass of the composite powder. The self-lubricating microparticles include a CaF2 self-lubricating core layer and a NiCr metal shell layer covering at least a portion of the surface of the CaF2 self-lubricating core layer. The preparation method of the composite powder includes: S31. Mix WC hard carbide powder and CoCr metal-bonded powder to obtain hard base powder; S32. Self-lubricating microparticles are added to hard base powder, and the composite powder is obtained by low-shear mixing and spray granulation.

[0052] Example 2

[0053] This embodiment provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Embodiment 1, except that: In S3, a composite coating is formed by spraying composite powder with supersonic air fuel in the annular sealing zone area. In S4, after grinding and fine polishing of the composite coating, the surface roughness Ra of the sealing working surface is 0.04μm. The self-lubricating microphase located near the surface of the composite coating is locally truncated, so that the CaF2-BaF2 composite self-lubricating core layer forms discrete friction-reducing micro-regions on the sealing working surface. The composite powder comprises Cr3C2 hard carbide powder with a D50 of 25 μm, NiCr metal-bonded powder with a D50 of 20 μm, and self-lubricating microparticles with a D50 of 8 μm; wherein the self-lubricating microparticles account for 5% of the total mass of the composite powder, and the self-lubricating microparticles comprise a CaF2-BaF2 composite self-lubricating core layer and a CoCr metal shell layer covering at least a portion of the surface of the self-lubricating core layer; the preparation method of the composite powder includes: S31. Hard base powder is obtained by mixing Cr3C2 hard carbide powder and NiCr metal bond powder. S32, Same as Example 1.

[0054] Example 3

[0055] This embodiment provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Embodiment 1, except that: In S3, a composite coating is formed by supersonic flame spraying of composite powder in the annular sealing zone area. In S4, after grinding and fine polishing of the composite coating, the surface roughness Ra of the sealing working surface is 0.03μm. The self-lubricating microphase located near the surface of the composite coating is locally truncated, so that the BaF2 self-lubricating core layer forms discrete friction-reducing micro-regions on the sealing working surface. The composite powder comprises WC-Cr3C2 hard carbide powder with a D50 of 45 μm, NiCrMo metal-bonded powder with a D50 of 30 μm, and self-lubricating microparticles with a D50 of 15 μm; wherein the self-lubricating microparticles account for 8% of the total mass of the composite powder, and the self-lubricating microparticles comprise a BaF2 self-lubricating core layer and a NiCrMo metal shell layer covering at least a portion of the surface of the self-lubricating core layer; the preparation method of the composite powder includes: S31. Mix WC-Cr3C2 hard carbide powder and NiCrMo metal-bonded powder to obtain hard matrix powder; S32, Same as Example 1.

[0056] Example 4

[0057] This embodiment provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Embodiment 1, except that: In S3, a composite coating is formed by spraying composite powder with supersonic air fuel in the annular sealing zone area. In S4, after grinding and fine polishing of the composite coating, the surface roughness Ra of the sealing working surface is 0.05μm. The self-lubricating microphase located near the surface of the composite coating is locally truncated, so that the BaF2 self-lubricating core layer forms discrete friction-reducing micro-regions on the sealing working surface. The composite powder comprises TiC powder with a D50 of 30 μm, FeCoNiCrMo metal-bonded powder with a D50 of 12 μm, and self-lubricating microparticles with a D50 of 12 μm; wherein the self-lubricating microparticles account for 3% of the total mass of the composite powder, and the self-lubricating microparticles comprise a BaF2 self-lubricating core layer and a CoNiCr metal shell layer covering at least a portion of the surface of the self-lubricating core layer; the preparation method of the composite powder includes: S31. TiC powder and FeCoNiCrMo metal-bonded powder are mixed to obtain hard matrix powder; S32, Same as Example 1.

[0058] Comparative Example 1 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 2, except that the composite powder includes Cr3C2 hard carbide powder with a D50 of 25μm and NiCr metal bonded powder with a D50 of 20μm; that is, no self-lubricating microparticles are added.

[0059] Comparative Example 2 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 2, except that: In the composite powder, the self-lubricating microparticles are not equipped with a metal shell. The uncoated CaF2-BaF2 self-lubricating powder is directly added to the hard base powder for mixing and spray granulation. The self-lubricating powder accounts for 5% of the total mass of the composite powder, and its D50 is 8μm.

[0060] Comparative Example 3 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 3, except that the self-lubricating microparticles account for 12% of the total mass of the composite powder.

[0061] Comparative Example 4 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 1, except that: the pretreatment of S21 is not performed between S2 and S3, that is, the annular sealing strip area is not degreased, sandblasted, roughened, and surface cleaned. Instead, supersonic spraying is performed directly on the annular sealing strip area.

[0062] Comparative Example 5 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 2, except that the composite powder is not sprayed and granulated. Instead, Cr3C2 hard carbide powder, NiCr metal bond powder and CaF2-BaF2 self-lubricating microparticles are directly mechanically mixed and then sprayed with supersonic air fuel.

[0063] Comparative Example 6 This comparative example provides a ball valve ball and its supersonic spraying process. The supersonic spraying process is the same as in Example 2, except that supersonic air fuel spraying is replaced with ordinary plasma spraying.

[0064] Performance testing The following performance tests were conducted on Examples 1-4 and Comparative Examples 1-6, and the results are shown in Tables 1-5. Test the thickness of the composite coating: Take a sample from the annular sealing zone of the ball valve ball, after embedding and polishing, observe the cross section of the composite coating under a metallographic microscope, and measure the coating thickness at no less than 5 positions along the length of the coating. Take the average value as the thickness of the composite coating. Surface roughness of the sealing working surface was tested using a surface roughness tester. The results are shown in Table 1. Table 1

[0065] As shown in Table 1, Examples 1 to 4 can all form composite coatings with a thickness of 100 to 400 μm, and after grinding and fine polishing, the surface roughness Ra of the sealing working surface is 0.03 to 0.08 μm.

[0066] Test the area ratio of discrete friction-reducing micro-regions: The sealing working surface after grinding and fine polishing was observed using a scanning electron microscope. Based on the area of ​​the self-lubricating core layer exposed area in the microscopic image and the total area of ​​the detection image, the ratio of the area of ​​the self-lubricating core layer exposed area to the total area of ​​the detection image was calculated as the area ratio of the discrete exposed area on the sealing working surface. The results are shown in Table 2. Test the equivalent circle diameter of discrete exposed areas: Measure the projected area of ​​each discrete exposed area in the microscopic image, and calculate the diameter of a circle with the same projected area as the discrete exposed area. The result is shown in Table 2. Test whether a circumferentially continuous lubricating phase is formed: Continuous observation or segmented splicing observation is carried out along the circumference of the annular sealing zone area to determine whether a lubricating phase extending continuously along the circumference of the annular sealing zone is formed in the exposed area of ​​the self-lubricating core layer. The results are shown in Table 2. Table 2

[0067] As shown in Table 2, the discrete exposed areas in Examples 1-4 are distributed in at least one of the following forms on the sealing working surface: dot-like, island-like, or short strip-like. Furthermore, no lubricating phase extending continuously along the circumferential direction of the annular sealing zone is formed between the discrete exposed areas. This indicates that the present application can expose the self-lubricating microphase in a discrete form on the sealing working surface, thereby providing local friction reduction while avoiding the formation of continuous soft lubrication channels. In Comparative Example 3, due to the excessively high content of self-lubricating particles, the area ratio of the discrete exposed areas increases, the equivalent circle diameter exceeds the range defined in this application, and a lubricating phase extending continuously along the circumferential direction of the annular sealing zone is formed locally. This indicates that an excessively high content of self-lubricating particles can lead to local enrichment or continuity of the self-lubricating phase, thereby affecting the load-bearing stability and sealing reliability of the sealing working surface.

[0068] Test the porosity of the composite coating: The composite coating in the annular sealing zone was prepared into a cross-sectional sample. After mounting and polishing, the cross-sectional image of the composite coating was obtained under a metallographic microscope. The pore area was identified by image analysis software, and the proportion of the pore area to the total area of ​​the detected image was calculated as the porosity of the composite coating. The results are shown in Table 3. Composite coating bonding strength test: After the sample with the composite coating is bonded and cured with the paired tensile part by high strength adhesive, a tensile test is performed on a universal testing machine. The maximum load when the composite coating peels off from the spherical substrate or the sample is broken is recorded. The bonding strength of the composite coating is calculated based on the maximum load and the bonding area. The results are shown in Table 3. Table 3

[0069] As shown in Table 3, the composite coatings of Examples 1-4 have low porosity, indicating that a relatively dense composite coating can be formed by supersonic spraying; the composite coatings of Examples 1-4 have high bonding strength, indicating that hard carbide powder, metal bonding powder and coated self-lubricating microparticles can jointly form a stable composite coating.

[0070] Friction and wear performance testing: Friction and wear tests were conducted on the sealing working surface using a ball-disc or ring-block friction and wear testing machine. During the test, the composite coating sealing working surface was used as the friction pair surface and paired with the valve seat material or simulated valve seat material. Friction and wear tests were conducted under the same load, rotation speed and test time conditions. The average friction coefficient was recorded during the test. After the test, the wear track width or wear volume was measured, and the relative wear amount was calculated with the wear amount of Comparative Example 1 as the benchmark. The results are shown in Table 4. Table 4

[0071] As shown in Table 4, the friction coefficients and relative wear amounts of Examples 1-4 are all lower than those of Comparative Example 1, indicating that the self-lubricating microphases exposed on the sealing working surface can form a local friction-reducing effect in the contact area between the ball and the valve seat, thereby reducing frictional resistance and wear.

[0072] Test of opening and closing torque variation rate: The ball valve balls prepared in the examples and comparative examples were assembled into the ball valve test assembly of the same specifications. Under the same valve seat preload and sealing pressure conditions, the opening and closing cycle test was carried out to test the initial opening and closing torque and the opening and closing torque after the cycle opening and closing, and the opening and closing torque variation rate was calculated. The results are shown in Table 5. Sealing and leakage performance test: The ball valve balls prepared in the examples and comparative examples were assembled into ball valves of the same specifications, and the sealing performance was tested under the same pressure conditions; the test medium was air, water or a medium corresponding to the actual working conditions, and the results are shown in Table 5; Table 5

[0073] As shown in Table 5, the opening and closing torque change rate of Examples 1-4 is significantly lower than that of Comparative Examples 1-6, indicating that the discrete self-lubricating exposed area formed in this application can reduce the frictional resistance during the opening and closing process of the ball and slow down the increase in torque after the opening and closing cycle. Examples 1-4 can all meet the sealing requirements, indicating that while forming discrete friction-reducing micro-areas, this application can still maintain the continuous bearing capacity and sealing stability of the sealing working surface.

[0074] In summary, this application utilizes supersonic spraying of composite powder to form a composite coating in the annular sealing zone area of ​​the ball substrate. Through grinding and fine polishing, the sealing working surface includes exposed self-lubricating microphases. This enables the ball valve ball's sealing working surface to possess wear-resistant load-bearing capacity, friction-reducing and anti-scratch properties, and sealing stability. Furthermore, when the self-lubricating microparticles employ a coating structure consisting of a self-lubricating core layer and a metal shell layer, it can reduce the melting migration, dispersion, agglomeration, or interface debonding of the self-lubricating core layer during supersonic spraying, and improve the bonding stability between the self-lubricating microphase and the hard carbide load-bearing phase and the metal bonding phase, thereby extending the service life of the ball valve ball. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this invention; therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A supersonic spraying process for a ball valve ball, characterized in that, Includes the following steps: S1. Pre-process the spherical base to form the outer spherical surface, flow passage, and valve stem connection; S2. Determine an annular sealing band area on the outer spherical surface for sealing and mating with the valve seat; S3. Apply composite powder using supersonic spraying in the annular sealing zone area to form a composite coating; S4. Grind and polish the composite coating to form a sealing working surface, thus obtaining the ball valve ball. The composite powder includes hard carbide powder, metal-bonded powder, and self-lubricating microparticles. The composite coating comprises a hard carbide carrier phase, a metal bonding phase, and a self-lubricating microphase. After grinding and fine polishing, at least a portion of the self-lubricating microphase located near the surface of the composite coating is exposed on the sealing working surface. The sealing working surface comprises a hard carrier area and a discrete friction-reducing micro-area. The discrete friction-reducing micro-region includes a self-lubricating micro-phase exposed on the sealing working surface; the hard bearing region includes the hard carbide bearing phase and the metal-bonded phase.

2. The supersonic spraying process according to claim 1, characterized in that, The self-lubricating microparticles include a self-lubricating core layer and a metal shell layer covering at least a portion of the surface of the self-lubricating core layer; The self-lubricating core layer includes at least one of CaF2 and BaF2; The metal shell includes at least one of Ni, Co, Ni-P, Ni-Co, NiCr, CoCr, NiCrMo, and CoNiCr.

3. The supersonic spraying process according to claim 1, characterized in that, The hard carbide powder includes at least one of WC, Cr3C2, TiC, NbC, and VC; and / or The metal-bonded powder includes at least one of CoCr, NiCr, NiCrMo, CoNiCr, FeCoNiCr, and FeCoNiCrMo.

4. The supersonic spraying process according to claim 3, characterized in that, The method for preparing the composite powder includes the following steps: S31. The hard carbide powder and the metal-bonded powder are mixed to obtain a hard base powder; S32. The self-lubricating microparticles are added to the hard base powder, and the composite powder is obtained by low-shear mixing and spray granulation.

5. The supersonic spraying process according to claim 1, characterized in that, Between S2 and S3, there is also: S21. Pre-treatment of the annular sealing strip area, the pre-treatment including degreasing and cleaning, sandblasting roughening and surface cleaning treatment.

6. The supersonic spraying process according to claim 1, characterized in that, The self-lubricating microparticles account for 0.5-8% of the total mass of the composite powder.

7. The supersonic spraying process according to claim 1, characterized in that, The D50 of the hard carbide powder is 10~45μm; The D50 of the self-lubricating microparticles is 5~15μm; The thickness of the composite coating is 100~400μm.

8. The supersonic spraying process according to claim 1, characterized in that, The discrete friction-reducing micro-regions are separated by the hard carbide carrier phase and / or the metal bonding phase, and the discrete friction-reducing micro-regions account for 0.3~6% of the area of ​​the sealing working surface.

9. The supersonic spraying process according to claim 1, characterized in that, In S3, the supersonic spraying includes supersonic flame spraying or supersonic air-fuel spraying.

10. A ball valve ball, characterized in that, It is prepared by any one of the supersonic spraying processes according to claims 1 to 9. The ball valve ball includes a ball base and a composite coating formed on the annular sealing zone region of the ball base; the sealing working surface formed by the composite coating includes a hard bearing area and a discrete friction-reducing micro-area, the discrete friction-reducing micro-area includes a self-lubricating micro-phase exposed on the sealing working surface; the hard bearing area includes a hard carbide bearing phase and a metal-bonded phase.

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