NUCLEATION AND GROWTH OF DIAMOND AND DIAMOND-LIKE COATINGS PRODUCED BY TORCH TECHNIQUE

Oxygen/acetylene combustion flame (torch) technique was employed to investigate the nucleation and growth characteristics of diamond/diamond-like (DL) coatings. The substrate used was pure polycrystalline molybdenum subjected to a range of mechanical and other polishing procedures. The results obtained have shown that optimization of the substrate preparation procedure can achieve improvement in nucleation density in excess of an order of magnitude. Also a maximum growth rate, within the substrate temperature range of450-1050°C, was observed. Although the coatingsʹ thickness increased as deposition time increased, the effect was more pronounced for deposition time less than 100 minutes. Conversely, the growth rate decreased as the oxygen/acetylene gas ratio (R) increased. The effect was far more pronounced for R values exceeding 0.9. Also, interesting changes in crystal morphology controlled by changes in substrate preparation and R values have been observed.