Improving tribological properties of sputtered boron carbide coatings by process modifications

Boron carbide coatings are well-known for extreme hardness and excellent we ar resistance. In this paper a d.c. magnetron sputter process for the depos ition of boron carbide coatings is described. It is shown that by adding sm all amounts of a hydrocarbon reactive gas (in this case acetylene) the coef ficient of friction can be reduced from 0.8 down to 0.2. Results from a lab oratory scale deposition device are successfully transferred to an industri al batch coater. The coating adhesion is well enhanced by a titanium interl ayer. From the analysis of the chemical composition and from hardness value s it is concluded that a structural modification is responsible for the imp rovement of sliding behaviour. It is suggested that the introduction of add itional bondings reduces the brittleness of boron carbide. Furthermore, a c omparison with metal-containing amorphous carbon coatings (Me-DLC) reveals several similarities. (C) 2000 Elsevier Science S.A. All rights reserved.