Chemical vapour deposition of diamond on nitrided chromium using an oxyacetylene flame

In this paper we present our first preliminary results on chemical vapour d eposition (CVD) of diamond onto nitrided chromium using an oxyacetylene fla me. Polycrystalline diamond films were obtained after deposition at very lo w substrate temperatures (<400 degrees C). At these low temperatures there was extremely weak bonding, or no bonding at all, between the deposited lay er and the substrate. To obtain stronger bonding, four growth experiments w ere carried out at initially higher substrate temperatures (700-1000 degree s C). Whilst growth continued, the substrate temperatures were lowered step by step to 250 degrees C. It was observed that on lowering the substrate t emperature by more than about 500 degrees C from the initial temperature, d elamination occurred, suggesting that the thermal stresses exceeded the bon ding strength. Subsequently, adherent diamond coatings were grown on the fr eshly exposed substrate surface whilst further lowering the substrate tempe rature. These diamond coatings were characterized using scanning electron m icroscopy and the adhesion of the diamond coatings to the substrates was as sessed by means of the scotch tape test. (C) 2000 Elsevier Science S.A. All rights reserved.