NITROGEN IMPLANTATION OF TI AND TI+AL FILMS DEPOSITED ON TOOL STEEL

Titanium and aluminum thin films were deposited onto A2 steel by rf magnetron sputtering with various Al contents. The coated assembly was then implanted with nitrogen ions at 92 kV and ? mA for 4.5 h. The thickness of the implanted Ti and Ti+Al films deposited for I h was around 0.4-0.5 mu m. With the aid of X-ray diffraction by the grazing-incidence technique, secondary ion mass spectrum (SIMS) and X-ray photoelectron spectroscopy (XPS), the titanium oxide and titanium nitride were identified on the top and inner surface in the implanted Ti film. For Ti+Al films after nitrogen implantation, Ti3O5 was formed on the top surface beneath which is a (Ti,AI)N solid solution. There was Ti2N compound formed in the implanted Ti film, while only a minor amount of Ti2N phase was observed in the inner region in the implanted Ti+Al film. The nitrogen distribution was flattened and spread in the implanted Ti film, while a concentration gradient was observed in the Ti+Al film after implantation. The measured surface hardness of implanted Ti film was higher than those of Ti+Al films and the hardness of implanted Ti+39%Al film was enhanced as compared to the Ti+50%Al film.