Diamond coatings for tool shafts by induction plasma deposition
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文摘
Induction plasma torches have inherent properties such as large plasma volume, generated without electrodes, with high plasma temperatures (10 000 K) and axial injection capability. The potential benefits for diamond synthesis are large coverage as well as high growth rate. In this paper, induction plasma was used to synthesise diamond layers, without diamond preseeding, and the diamond growth (axially and radially) was investigated as a function of various thermal boundary layers thicknesses determined by emission spectroscopy. The small diameter substrate (4.76 mm) was used to probe the diamond quality as a function of the homogeneity of the generated plasma in order to get data on diamond growth all along the large plasma diameter. The results have shown that the gas velocity strongly influences the thermal boundary layer thickness as well as the radial growth of the diamonds. This was demonstrated by SEM as well as roughness measurements. The reduction of the overall diffusion time by the decrease in the boundary layer thickness can consequently improve the growth of the lateral faces of the diamond which are less directly seen by the plasma gases.