Improvement of Wear Characteristic of Partially Stabilized Zirconia by Peening

Abstract

To investigate the effects of shot peening (SP) on the wear resistance of ceramics, wear tests were performed on two materials. Rectangular plate test specimens of partially stabilized zirconia (PSZ) and silicon nitride (Si₃N₄) were subjected to SP. The surface characteristics and the mechanical properties, including surface roughness, Vickers hardness, residual stress, and apparent fracture toughness, were measured on non-SP, SP, and SP and polished (SP-P) specimens. Ball on plate tests were carried out using PSZ and Si₃N₄ specimens in air under dry condition and the wear volumes were investigated. SP induced a compressive residual stress on the surface of the specimens, resulting in an improvement in the Vickers hardness and the apparent fracture toughness near the surface. The wear resistance of Si₃N₄ specimens was improved by SP and SP-P; however, that of PSZ specimens was reduced by SP due to the presence of micro-cracks caused by phase transformation, which involves a volume expansion. The wear resistance of PSZ specimens was improved after SP-P due to the increased Vickers hardness and the removal of the micro-cracks introduced by SP. These results indicated that it is essential to increase the surface hardness and eliminate the micro-cracks present on the surface in order to improve the wear resistance of ceramics.