Acoustic Microscopy of Ceramic Surfaces

Mechanical properties of ceramic surfaces such as hard- ness, indentation fracture toughness, and wear resistance are largely influenced by the behavior of small flaws and defects, such as micro- cracks, delaminations, voids, and inclusion located beneath the sur- face. Acoustic microscopy is particularly suited to study this phenom- enon because it can image microscopic subsurface features without sectioning. Furthermore, it has been revealed that the velocity and at- tenuation of the leaky surface wave can be measured; these are ex- pected to have close correlation with the mechanical properties of ma- terials. New results on the nondestructive observation of subsurface cracks of Si,N, and ZrO, and delamination of TIN coatings introduced by Vickers indentation or sliding contacts are presented. The mecha- nism of delamination and wear of these materials is discussed. It is shown that the velocity and attenuation of the leaky surface wave of TIN coatings and sintered AlzOn actually have close correlation with the hardness and wear resistance of these materials. The reason for these correlations is also discussed.