Low residual stress diamond coatings on titanium

Diamond coatings on pure titanium substrates are of interest for tribological and biomedical implants, among others, however, due to the different thermal expansion coefficients of the two materials, it is difficult to grow adherent thick diamond layers on Ti. The aim of this work was to investigate the influence of cooling down the substrate from the deposition temperature to the room temperature and then repeat the deposition process several times, on the quality and stress of the deposited diamond. This process intended to allow a partial relaxation of the diamond/Ti thermal stresses by accommodating the diamond nuclei onto the titanium carbide formed interlayer without detachment from the substrate. A hot-filament chemical vapor deposition system fed with ethanol, highly diluted in hydrogen was employed. Coatings of complete surface coverage with faceted grains of lateral size of about 4 μm and 0.38 GPa have been obtained.