Combined Anti-Friction Coatings Based on Nichrome and Copper

Abstract

This work examines combined antifriction coatings obtained by electric spark processing of a metal substrate with an electrode made of the X20N80 alloy, followed by filling discontinuities, depressions, and pores with copper powder. Copper powder was applied using supersonic gas-dynamic spraying. The combined coatings under study had a thickness of 60–350 μm. The work also obtained the dependences of the friction coefficients for coatings with different surface areas of the electric spark and copper components. The magnitude of the friction coefficient depends on the applied load. It was found that the minimum friction coefficient for coatings was in the range of 0.077–0.142. The pressure values for the appearance of plastic contact for various types of experimental coatings are in the range of 178–241.5 MPa. Coatings with a higher percentage of copper on the surface, other things being equal, have a lower temperature in the friction zone. Reducing the area of the electric spark component from 78 to 4% makes it possible to reduce the temperature in the friction zone by 2.5 times. At a relative sliding speed of 55 m/min, a self-lubricating effect is observed. The quasi-liquid form of copper is fragmentarily transferred into the roughness cavities of the electric spark component. As a result of the research, combined antifriction coatings with a surface area of the electric spark component of less than 50% are recommended for use in friction units with contact pressure up to 240 MPa; in pairs with contact pressure below 170 MPa, coatings with an area of the electric spark component of 4–30%, having low coefficient of friction.