Microstructure And Tribology Properties Of ZnO Doped Mg-PSZ Ceramics

PSZ ceramics based on Mg-PSZ with a molar rate of 10:90 of MgO: ZrO₂ were prepared by adding different content of ZnO. Mechanical properties were measured by three point flexural test and hardness test. Tribology properties were also examined under a simulated circumstance of wire drawing. The microstructure characteristics and phases constitute were identified by SEM and XRD. The effects of different content of ZnO on microstructures and mechanical properties were investigated. The tribology properties of different PSZ systems under different frictional rings, rotation rate, and normal load were also analyzed.The experiment results show that a new compound were formed by the reaction of ZnO and ZrO₂ and induced the aberration of crystal lattice, which lead to a low sintering temperature and small grain size. Compared with the traditional Mg-PSZ, a amount of t-ZrO₂ phase precipitated directly from the (Zn,Mg)-ZrO₂ matrix during the cooling process without a long-time heat-annealing. It simplified the producing process and decreased the cost.The ZnO content had an effect on the shape of t-ZrO₂ precipitates. As the increasing of the ZnO content, the size of the grain became bigger, and its shape changed from sphere to multi-sides one which was anisotropism. The mechanism provided evidence for the controlling and exploitation of the properties of the ceramics.Among the samples doped with zinc oxide, the average bending strength of samples with 0.4mol% ZnO reached to 703.5±47.3MPa. but for the different forming mechanism of t-ZrO₂, it showed a lower toughness than that of Mg-PSZ, which was 7.8MPam^1/2 . Considering the lower toughness, Mg-PSZ ceramics doped with ZnO can only be used in such an environment that does not require a high toughness.The friction behaviour between steel wire of 65Mn and different zirconia based ceramic rings, such as 0.4ZnO-10MgO-ZrO₂,10MgO-ZrO₂ and Y-TZP, is done respectively under a simulated circumstance of wire drawing. It showed that zirconia based ceramics had good properties of tribology that wear rate came to a stabilization after 10h with a value between 10^-6～10^-7. And Y-TZP is the best one. Because of the complicated reactions between water and zirconia based ceramics, wear rate value is smaller in the oil than in the water. And Mg-PSZ had a break of wear rate when sliding in the water. Through the research, we also found the following rules: the increasing of rotational rate decreased the wear rate of ceramics; the bigger of the normal load, the higher of the wear rate. They can all provide reference when the ceramics with zirconia matrix are used as module of wire drawing. The results can be used to guide the application of zirconia based ceramic parts in different environments.