Microstructure, mechanical and tribological properties of PACVD Ti(B,N) and TiB2 coatings

Coatings within the system Ti–B–N have been deposited onto tool steels using commercial Rübig plasma-assisted chemical vapour deposition plants. The boron content has been varied in a wide range between single-phase TiN and single-phase TiB2. X-ray diffraction spectra for intermediate boron contents indicate a nanocomposite arrangement of TiN and TiB2 based phases. The coatings have been characterized with respect to their microstructure, mechanical and tribological properties. The increasing boron content leads to an increase in hardness and wear resistance. Compressive stress within the coatings rises significantly with boron content which demands the realization of multi-layer structures to achieve good adhesion. Ti(B,N) coatings show a friction coefficient of approximately 0.4 at high humidity and approximately 0.9 at low humidity.