Early stage cavitation erosion within ceramics—An experimental investigation

Six ceramic material types were considered within an experimental investigation to identify the erosion damage mechanisms resulting from cavitation exposure. These materials were a Y-TZP-type zirconia, different commercially available silicon nitrides, a high-purity alumina and a hardened high-nitrogen stainless steel as reference. An ultrasonic transducer was utilised to produce cavitation conditions and the configuration was “static specimen method” using a 5-mm diameter probe, 20-kHz and 50-μm amplitude. The exposure times were periods from 15 s to 3 h. Experimental methods employed to characterise wear mechanisms were light microscopy, scanning light interferometry and scanning electron microscopy. It was found that the zirconia and silicon nitrides demonstrated evidence of local pseudo-plastic deformation or depression prior to more pronounced erosion damage by fracture. Zirconia showed evidence of delayed surface changes when the sample is at rest stored in air, possibly by spontaneous phase transformation after the completion of the erosion tests. Alumina showed evidence of brittle surface fracture and negligible or no pseudo-plastic deformation. All wear mechanisms are discussed, and the materials are ranked in terms of cavitation resistance performance.