Adhesion, friction and wear of thin hard coatings

Abstract

Chemically vapour-deposited and physically vapour-deposited coatings of hard and wear-resistant materials such as TiC, TiN, Ti(C, N), Cr7C3, Al2O3, SiO2 and TiO2 as well as other carbides, nitrides, borides, oxides and combinations thereof are increasingly used in industrial applications to protect metal, ceramic and in certain cases polymer parts against mechanical and chemical attack, sometimes with a decorative purpose also. Some relevant examples of coated products are cemented carbide throwaway cutting tips (TiC, TiN, Ti(C, N), Al2O3 etc.), high speed steel drills and milling cutters (TiN), hobs, deep drawing tools, ball-bearing elements, gears, machine elements, electrical contacts, body implants, surgical instruments and tools, cutlery, fuel pins and armatures especially for helium- and sodium-cooled nuclear reactors, low Z sputter-resistant protective coatings on parts (limiters, antennae etc.) and walls of the torus in fusion reactors (tokamak) and gold- or silver- or black-coloured watch cases and jewelry pieces. The life of such coated tools or machine elements as well as their performance are considerably increased, provided that the adhesive strength of the coating to the base material and the intrinsic cohesion of the coating are sufficient. Bad adhesion leads to flaking (adhesive failure) while poor cohesion causes chipping (cohesive failure). © 1984.