CHARACTERIZATION OF DIAMOND FILMS DEPOSITED ON TITANIUM AND ITS ALLOYS

Titanium and its alloys have important applications for example in aer ospace or as bioimplants. Some of these applications would be improved by diamond coatings. However the large thermal expansion mismatch bet ween diamond and titanium or its alloys creates high residual stresses , up to about 7 GPa at 800 degrees C, which represent an important dra wback. In this study, polycrystalline diamond films were deposited on pure titanium and Ti-6A1-4V in a classical tubular microwave plasma re actor from C-H(-O)-containing gas mixtures, at a temperature in the ra nge 600-900 degrees C. Raman spectroscopy provided information about t he diamond grain stress, which is obviously related to the deposition temperature. X-ray diffraction indicates the presence of titanium carb ide or oxycarbide. Some other characterizations by Xray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electro n energy loss spectroscopy (EELS) are reported. It is shown that XPS c oupled to argon ionic etching allows us to study the first steps of th e deposition process. The structure and the chemical composition at th e interface of a thicker deposit are obtained by TEM and EELS.