Coating of Austentic Stainless Steel with Ti/O Compositionally Gradient Film by Reactive DC Sputtering

Abstract

Coating of austentic stainless steel substrates with Ti/O compositionally gradient film was examined using reactive DC sputtering technique, in order to improve not only the abrasion resistance of the stainless steel but also the adhesion between the deposited film and the substrate with preserving the high hardness of such a hard ceramic coating as titanium oxide coating. The deposition of Ti/O compositional gradient films were realized by varying continuously the oxygen content in Ar-O2 sputter-gas during the reactive sputtering. The obtained films were appeared to be uniform and adhesive, while Ti-O compositional constant (i.e. non-gradient) films which were deposited by reactive DC sputtering under the same sputtering conditions except for the Ar-O2 gas mixing condition, i.e., with the oxygen content in the gas mixture constant, peeled off partly. According to AES in-depth profiles, the oxygen (O) concentration in the obtained film gradually decreased in depth direction from the surface toward the substrate, confirming that Ti/O compositional films had formed on the stainless steel. On the basis of XRD, it was found that not only hcp alpha-titanium and titanium oxide (anatase) but also some types of suboxides had formed in the gradient films. Furthermore the gradient films approximately indicated Hv600 which was much higher than that of the stainless steel substrate. Therefore the abrasion resistance of the stainless steel and the adhesion at the interface were expected to be improved at the same time.