ADHERENT NANO-SUPERHARD TITANIUM NITRIDE FILM AND ITS FORMING MECHANISM IN MULTI-ARC ION-PLATING SYSTEM

An adherent nano-superhard titanium nitride (TiN) film on the substrate of Cr12Mo4V high speed steel was prefabricated in a vacuum cathode multi-arc ion-plating system. Microhardness, film-to-substrate adhesion, and microstructure of the film were investigated typically using Vickers hardometer, scratch tester, and X-ray diffractometer. Results show that: (i) the achievable film microhardness is in the range of 35–45 GPa; (ii) the critical load (Lc) of the superhard TiN film is approximately 64 N; (iii) the nm scale mean main grain sizes of the film are approximately of 12.7 nm for TiN111, 19.7 nm for TiN200, and 9.6 nm for TiN220; and (iv) compared with the standard TiN film with the hardness of 22 GPa, the accomplishment of the nano-superhard TiN film may be due to (a) the ion bombardment induced residual stress within the film, and (b) the combined effect of the decrease of crystalline size and preferred orientation in the plane (111).