2-STEP PROCESS FOR IMPROVED DIAMOND DEPOSITION ON TITANIUM-ALLOYS AT MODERATE TEMPERATURE

A simple two-step process is reported here to deposit diamond coatings on titanium alloys at temperatures equal to or lower than 600 degrees C. The first step allows us to increase the carbon nucleation rate an d to deposit a sacrificial layer which contains more than about 25% sp (2) carbon. Its thickness is selected both to limit the interaction of titanium element with the plasmas used for diamond growth during all the second step, even when an oxygen-containing mixture is used, and t o diffuse completely at the end of the process. After the first step, the formation of titanium carbide is observed by x-ray diffraction and x-ray photoelectron spectroscopy, which does not reveal any oxygen in corporation in the coating-substrate interfacial region. These results are related to the final strong diamond adherence. (C) 1998 American Institute of Physics.