Early Stage Cavitation Erosion within Ceramics: An Experimental Investigation.

Abstract

Six ceramic material types were considered within an experimental investigation to identify the erosion damages mechanisms resulting from cavitation exposure. These materials were a Y-TZP type of zirconia, different commercially available silicon nitrides, a high purity alumina and an hardened high nitrogen stainless steel. An ultrasonic transducer was utilised to produce cavitation conditions and the configuration was “static specimen method” using a 5mm diameter probe, 20kHz and 50μm of amplitude. The exposure times were periods from 15 seconds to 2 hours. Experimental methods employed to characterise wear mechanisms were light microscopy, scanning light interferometry, scanning electronic microscopy. It was found that the zirconia and silicon nitrides demonstrated evidence of local pseudoplastic deformation or depression prior to more pronounced erosion damages 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.