Tribological and protective coatings by chemical vapour deposition

Abstract

When steel and nickel-based alloys are to be used as substrate materials for the chemical vapour deposition of hard wear-resistant and corrosion-protective coatings because of their high mechanical strength, the criteria for choosing the correct grade have to be established. In this paper we contribute towards this goal. We also discuss the friction and wear behaviour of a number of refractory coatings, such as TiC, TiN, SiC, Cr 7C 3, Fe x B and Al 2O 3, under different environmental conditions. Some industrial tribological applications at moderately high temperatures (350°C in a helium atmosphere) or where the environment precludes the use of fluid lubricants are presented to illustrate the technical and economic feasibility and the usefulness of such coated machine elements and wear parts. Finally we deal with a very special application, the industrial exploitation of which is only just beginning: a multiple refractory compound coating to improve the protection of niobium tubes in the core of a nuclear reactor from damage due to metallurgical corrosion by liquid steel at high temperature (1600°C) which would result from accidental failure of a fuel pin.