Abstract

Tribological properties in narrow and broad senses were measured for cubic boron nitride films made by ion plating with or without subsequent ion implantation to increase adhesion of the films. First, a pure tribological property, such as the frictional coefficient, against stainless steel and diamond indenters was investigated for a c-BN film made with graded composition control through a titanium interlayer in air (for both indenters) and vacuum (for diamond indenter). The film showed a very good value (about 0.025-0.03) in both environments. We then report on the trial application of our c-BN film, believed to have a good tribological property, to a more practical tribological use, i.e., as a protective coating for drills. The tested WC-Co alloy drills had a c-BN coating or film made by ion plating and modified with the post-treatment of ion implantation to improve adhesion. The modification substantially increased the adhesion and the frictional property as well, resulting in substantial decrease of the thrust compared with the conventional TiCN coating.