Plasma sprayed wear-resistant coating

       

Wear-resistant coatings are a widely used field of plasma spray technology. Wear takes many different forms, depending on friction conditions and mechanisms. Four basic types are common: wear, bonded wear, fatigue wear, and corrosive wear.

① The basic requirements of wear-resistant particle wear coatings are high hardness and good oxidation resistance at working temperature. When the service temperature is ≤540℃, the coating can withstand scratches and furrows from external abrasives. The coating hardness should exceed the abrasive hardness. Typically used for mud pump piston rods, polishing rod bushings, mixer screw conveyors, tobacco grinding boundaries, mandrels, polishing rotors; when the operating temperature is 538~843℃, the coating has good oxidation resistance and high temperature hardness , which are typically used for wearing parts of various high temperature abrasives in the steel industry.



② Anti-stick wear coating A support material coating with high wear resistance. The coating has the characteristics of good lubricity. It is usually used for high loads and low speeds. The surfaces are generally of equal hardness. Generally the wear rate increases with increasing temperature. Rough surfaces have high wear rates but also provide recessed areas to store abrasive particles. Stamping shock absorber crankshaft, anti-friction bushing, directional ostrich bearing, turbine shaft, driving gear journal, piston ring fuel pump rotor, etc.



③ The fatigue wear-resistant coating is the wear of repeated sliding, rolling and impact under cyclic load. It should have high hardness and good toughness, avoid brittleness, have a small tendency to crack, not contain hard non-metallic inclusions, and be able to withstand the impact of gas in the liquid flow, and withstand high-speed erosion of sharp hard particles at different angles. It is typically used in turbine blades, wear rings, nozzles, diesel cylinder liners, steam turbine flow components, exhaust fans, powder discharge blades, impellers, hydroelectric valves, and cyclone dust collectors.



④ Corrosion and wear-resistant coating is the wear form of corrosion and wear, which is divided into oxidative wear and special medium wear. It must have comprehensive properties of corrosion resistance and wear resistance, and can resist the corrosion of special media such as acid, alkali and salt. Corrosion-resistant coatings are divided into atmospheric corrosion-resistant coatings and dipping corrosion-resistant coatings: atmospheric corrosion-resistant coatings are generally made of Zn, Al or Zn-Al alloys, which not only have cathodic protection, but also have good atmospheric corrosion resistance. . In different atmospheric environments, its corrosion rate is much lower than that of steel, and the effect of steel structures applied in marine atmospheric environments is remarkable.



The corrosion-resistant coating should be able to withstand corrosion in environments above or below the liquid level. When using fresh water storage containers, pipelines or contact materials, it must be ensured that the chemical composition and toxic and hazardous substances of drinking water cannot be changed. The requirements for non-potable water can be slightly lower, but they cannot be polluted. Hot fresh water refers to expensive hot water, which is characterized by higher temperature, so corrosion is more serious than normal temperature water. Salt water is more corrosive than ordinary fresh water. Liquids related to the food industry are generally not corrosive, but their composition is complex, involving various foods, beverages, dairy products, oils, fuels and solvents. Zinc and aluminum coatings are often used to protect the above-mentioned liquid immersion corrosion, and are generally closed. Coatings resistant to chemical media should be able to withstand various acids, alkalis, salt solutions, steam and solid corrosion. Various metal ceramics such as iron-based, nickel-based, cobalt-based alloys, oxide ceramics, etc. are mainly used.