Diamond films grown on cemented WC-CO dental burs using an improved CVD method

A modified hot-filament chemical vapour deposition system was used to deposit adherent diamond films onto cutting edges of cemented tungsten carbide (WC-Co) dental burs. Generally, the as-grown films were found to be polycrystalline and displayed good coverage. Micro-Raman spectroscopy was used to characterise the stress distribution at three positions: (i) bur tip, (ii) middle of the bur and (iii) end of bur. The stress at the back, in the middle and at the tip of the bur was calculated to be -1.7, -2.3 and -3.4 GPa in compression, respectively. It was noted that the filament temperature, as measured by the two colour optical pyrometer, varied along the coils of the filament. The coiled filament was at higher temperatures around the central region as compared to the filament edges. The temperature of the cutting edges was higher at the tip of the bur compared to the middle and back of the bur. The cutting teeth were closer to the filament and therefore expected to be at a slightly higher temperature. Consequently, a thicker coating was deposited on the edges of the cutting teeth as compared to the flat bur base material.