Structural investigations of protective polycrystalline diamond coatings on titanium substrates

Thick titanium substrates were coated with conductive polycrystalline diamond films by means of the microwave plasma assisted CVD method. In general, the obtained films showed good adhesion and did not peel off the substrates regardless of residual stresses. These were released from the titanium specimens during the deposition process and gave rise to a noticeable deformation of the samples. The structural properties of the deposits were found to be depending on the substrate pre-treatment procedures (sandblasting) as well as the deposition conditions (carbon oversaturation). No evidence was found for the formation of titanium hydrides from the use of the hydrogen-rich plasma. Structural continuities (heteroepitaxy) in the Ti/TiC/Diamond interfacial layer as well as the key role of titanium oxide for the diamond nucleation are discussed.