Study of the structure and properties of protective coatings obtained by the method of electric spark alloying with SHS electrodes (review)

Abstract

Electric spark alloying (ESA) is a traditional method of obtaining protective coatings on the working surfaces of parts and mechanisms. A review of the results of studying the structure and properties of protective coatings obtained by the ESA method using SHS-electrodes is presented. Ceramic and cermet electrodes are obtained by the method of SHS-extrusion carried out under conditions of combustion processes with high-temperature shear deformation. SHS extrusion makes it possible to obtain electrodes with desired structure and properties in tens of seconds in one technological stage. The results on the study and application of electrode materials made of hard alloy materials, intermetallic compounds, materials based on the MAX-phase and ceramic materials with a nanoscale structure are presented. Analysis of the microstructure and properties of the formed alloy layers showed that the protective coating consists of at least two zones. The sizes of the structural wear-resistant components on the coating surface, usually correspond to their sizes in the original electrodes. When going in depth to the substrate, the grain size decreases and amounts to 20 – 100 nm. It is shown that a protective coating is formed on the surface which increases the mechanical and tribological properties. The presented results can be used in comparative tribological tests of hardened coatings, industrial tests of machined parts, etc.