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 m ixtures, at a temperature in the range 600-900 degrees C. X-ray diffra ction, scanning electron microscopy and Raman spectroscopy showed that 1-10 mu m diamond layers could be produced at 600 degrees C with a fa irly good crystallinity and residual stresses limited to about 5 GPa. The intrinsic properties of the heat-treated titanium alloys are maint ained at this tempering temperature and no spalling occurred when an a ppropriate pretreatment was carried out. Therefore we expect that diam ond-coated titanium alloys could be used for general engineering appli cations where a low friction coefficient, low wear rate and load-beari ng capacity are all necessary.