An FIB study of sharp indentation testing on plasma-sprayed TiO2

Instrumented sharp indentation is often employed for micromechanical investigation of thermal-spray coatings. However, rather complex dependencies of measured values on indentation load have been reported. To verify the possible influence of sub-surface cracking, Vickers and Berkovich indentations on plasma-spray TiO2 were sectioned by FIB. Remarkable sub-surface cracking was found for indentations performed on the coating cross-section, even for rather low loads (1 N). Much less sub-surface cracking occurs when indenting the top surface, indicating material anisotropy. This preliminary investigation highlights the need for thorough studies of sub-surface cracking during instrumented sharp indentation.