Hardness and wear resistance of tetragonal zirconia polycrystals, role of phase transformation

Abstract The hardness of ceramic is frequently taken as the key performance index to evaluate its wear resistance. As demonstrated in the present study, the hardness should not be taken as a sole index if a phase transformation is involved during the wear process. Two tetragonal zirconia polycrystals (TZPs) with a 15% difference in their hardness are prepared. A ball‐on‐disk self‐mated wear test is then conducted; their wear rates differ by an order of magnitude. Though the amount of monoclinic (m) phase in the worn disk is low, the m‐phase content in the wear debris is high. The phase and microstructure analyses confirm the role of phase transformation on wear resistance. Though a greater extent of phase transformation is a guarantee to the resistance to crack propagation, a thicker transformation surface layer could produce a larger amount of wear debris through a fatigue wear process.