Plasma sprayed carbon nanotube reinforced splats and coatings

Plasma sprayed composite coatings prepared from powders doped with 1 wt% CNT were characterized by their scratch resistance. Additionally, the scratch resistance of the splats obtained from one powder, namely, crushed alumina, was also investigated. The average splat diameter of the splat containing CNT was larger. CNT reinforced splats were more damage resistant as compared to those produced from the pristine powder. The estimated increase in the work of adhesion, while scratching the CNT reinforced coatings was 59-176% higher than their counterpart without CNT. This is attributed to CNT bridging across splats resulting in an improvement in coating properties. Other factors promoting coating adhesion were CNT anchorage in the asperities of the bond coat and enhancement of coating stiffness in the presence of CNT. In general, coating failure during scratching occurred owing to the formation of tensile crack and large area spallation ahead of the indenter.