Scratch induced damage in alumina splats deposited on bond coats

Scratch induced damage of splats produced from three alumina based powders deposited on two polished bond coats were studied using several scratching speed–normal load conditions. The factors affecting scratch resistance were splat thickness, substrate wetting by the splats and defects in splats. A Ni–Al bond coat was better wetted by the alumina splats and hence the splats deposited on this bond coat offered higher scratch resistance as compared to the other bond coat, namely, Ni–Cr. The scratch resistance of superimposed splats was higher owing to greater combined thickness and better wetting between like materials. The splats obtained from nanostructured powders had a low scratch resistance since the unmelted subparticles served as defects.