Formation of Ti/O compositional gradient film on Ti-6Al-4V alloy by reactive DC sputtering

Coating of Ti-6Al-4V alloy substrates with Ti/O compositional gradient films was carried our by reactive DC sputtering, not only to improve the biocompatibility and the surface hardness of the alloy but also to relax the stress concentrated at the interface between the film and the alloy. The compositional gradient was realized by varying continuously the oxygen content in Ar-O-2 sputter gas during depositing. Under AES, it was confirmed that a Ti/O compositional gradient film had formed on the alloy, and it was concluded that the oxygen atoms which had concentrated at the surface of the alloy substrate diffused into the titanium layer in the compositional gradient film. Based on the results of XRD, it was found that alpha-titanium phase was formed in the compositional gradient film with (002) orientation dominant during the film growth. Furthermore, based on indentation-fracture tests, it was concluded that this depositing method improved the adhesion of the deposited film to the alloy substrate and the toughness of the film. (C) 1998 Elsevier Science B.V. All rights reserved.