Kennametal Inc.
Control and characterization of texture in CVD .alpha.-Al.sub.2O.sub.3 coatings

Abstract:

CVD Alumina coating has been one of the most important materials for wear resistant application for many years. Recently, texture control in .alpha.-Al.sub.2O.sub.3 has attracted increasing attention due to the possibility to further improve the anisotropic properties such as thermal conductivity and mechanical properties. The influence of process parameters on textures is complex. In the present application, the influence of nucleation surface condition and H.sub.2S on the texture in CVD .alpha.-Al.sub.2O.sub.3 coatings has been investigated. It has been shown that without the addition of H.sub.2S, the crystal orientation in the Al.sub.2O.sub.3 coatings is primarily dominated by the nucleation surface condition, whereas the effect of reactant composition on texture is minimal. On the other hand, in the presence of H.sub.2S during growth, reactant composition also plays an important role in affecting the crystal orientation. This effect is likely due to the strong interaction between the Al.sub.2O.sub.3 surface and the H.sub.2S.