In this paper we present our first preliminary results on chemical vapour
deposition (CVD) of diamond onto nitrided chromium using an oxyacetylene
flame. Polycrystalline diamond films were obtained after deposition at
very low substrate temperatures (<400 degrees C). At these low temperatures
there was extremely weak bonding, or no bonding at all, between the deposited
layer and the substrate. To obtain stronger bonding, four growth experiments
were carried out at initially higher substrate temperatures (700-1000 degrees
C). Whilst growth continued, the substrate temperatures were lowered step
by step to 250 degrees C. It was observed that on lowering the substrate
temperature by more than about 500 degrees C from the initial temperature,
delamination occurred, suggesting that the thermal stresses exceeded the
bonding strength. Subsequently, adherent diamond coatings were grown on
the freshly exposed substrate surface whilst further lowering the substrate
temperature. These diamond coatings were characterized using scanning electron
microscopy and the adhesion of the diamond coatings to the substrates was
assessed by means of the scotch tape test. (C) 2000 Elsevier Science S.A.
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