Effect of annealing on fatigue behavior of partially stabilized zirconia

Abstract

Interest in applications of stabilized zirconia (PSZ) as dental material has recently increased. In a corrosive environment such as a living body, PSZ is subjected to a cyclic load and needs higher fatigue strength. In our previous paper, appreciable degradation occurred in the fatigue lifetime of yttria-doped tetragonal zirconia polycrystals (TZP). In this study, PSZ specimens were annealed for 100 h at temperatures of 200, 400 and 600°C in a low vacuum atmosphere to improve the fatigue resistance. Both static and cyclic fatigue tests were conducted on the annealed specimens under static four-point bending and under cyclic reversed plane bending, respectively. As a comparison, specimens without annealing were tested in the same way. The test results indicated that the lifetime appreciably increases in cycling fatigue under a low applied load in specimens annealed at the low temperatures of 200 and 400°C from that of specimens without annealing. It was supposed that the occurrence of fine microcracks accompanied by the phase transformation from tetragonal to monoclinic caused enlargement of the process zone in the wake field of a crack in cyclic loading and contributed to the increase of crack resistance.