Feasibility study of plasma sprayed Al 2O 3 coatings as diffusion barrier on CFC components

Carbon fibre reinforced carbon (CFC) materials are increasingly applied as sample carriers in modern furnaces. Only their tendency to react with different metals at high temperatures by C-diffusion is a disadvantage, which can be solved by application of diffusion barriers. Within this study the feasibility of plasma sprayed Al 2O 3 coatings as diffusion barrier was studied. Al 2O 3 coatings were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure, bonding to CFC substrates and thermal stability. The results showed that Al 2O 3 could be well deposited onto CFC substrates. The coatings had a good bonding and thermal shock behavior at 1060°C. At higher temperature of 1270°C, crack network formed within the coating, showing that the plasma sprayed Al 2O 3 coatings are limited regarding to their application temperatures as diffusion barrier on CFC components.