Coating of Ti-6Al-4V alloy substrates with Ti-N films by reactive d.c. sputtering

The coating of Ti-6Al-4V alloy substrates with Ti-N films by reactive d.c. sputtering in an Ar-N-2 gas mixture was examined to improve not only the blood compatibility but also the hardness and thereby the abrasion resistance of the alloy. The effects of discharge voltage on the formation of the Ti-N film were investigated. Under visual observation, the films deposited at various voltages appeared to be uniform and adhesive, whereas their colour tone varied with the voltage and the films obtained under a voltage of >400 V looked yellow-gold. With SEM, the surface of the films deposited under various voltages were observed to consist of fine particles. According to AES, the Ti/N ratio in the depth direction was nearly constant in each of the films. On the basis of x-ray diffraction, it was concluded that a Ti2N phase was formed predominantly in films deposited at 350 V whereas a TiN phase was formed predominantly in films deposited at a voltage of >400 V and the crystallinity of these phases was developed by heating the substrates to >400degreesC. Furthermore, it was found that the Vickers hardness Hv reached >2400 for films deposited at a voltage of >400 V onto the substrates and heated to >400degreesC. Therefore it was expected that the Ti-N films deposited onto the alloy substrates heated to >400degreesC under a voltage of >400 V could serve to improve not only the blood compatibility but also the hardness and thereby the abrasion resistance of the alloy. Copyright (C) 2002 John Wiley Sons, Ltd.