By adding of boron to the Ti-N coating, Ti-B-N coatings with boron contents from 5% to 16 % have been deposited on steels using activated ion plating. The effect of boron content on the microstructure and the properties of the Ti-B-N coating have been studied. A diffusion zone exists at the coating/substrate interface. TEM analysis indicates that the coating has a dense nanocrystalline composite structure and a crystal size smaller than 50 urn. The phase composition of the coating is fee TiN, simple orthorhombic TiB, cubic BN and simple hexagonal Ti-B-N. The mechanical properties, such as microhardness, toughness adhesion and sliding friction coefficient of the Ti-B-N coating are much better than those of the Ti-N coating, and the deposition temperature is much lOwer than that for the Ti-N coating.Correspondent: Yang Qiaoqin, Ph. D, Associate Professor, Material Test & Research Centre, Hunan University, Changsha 410083,P. R. China, Tel: 086-731-8822663