Diamond coating of titanium alloys at tempering temperature

Polycrystalline diamond films have been deposited on pure titanium and Ti-6Al-4V in a microwave plasma reactor from CH4-H-2 and CO-H-2 gas mixtures, at a temperature in the range 600-900 degrees C. X-ray diffraction, scanning electron microscopy and Raman spectroscopy showed that 1-10 mu m diamond layers could be produced at 600 degrees C with a fairly good crystallinity and residual stresses limited to about 5 GPa. The intrinsic properties of the heat-treated titanium alloys are maintained at this tempering temperature and no spalling occurred when an appropriate pretreatment was carried out. Therefore we expect that diamond-coated titanium alloys could be used for general engineering applications where a low friction coefficient, low wear rate and load-bearing capacity are all necessary.