Effects of nano MgO addition on the mechanical, wear, and low-temperature degradation properties of 3Y-TZP composite ceramics

In this study, 3 mol%-Y2O3-stabilized–tetragonal zirconia composite ceramics (3Y-TZP) with 0 wt%–1 wt% nano MgO content were prepared using an atmospheric pressure sintering method at 1,400 °C–1,600 °C. The microstructure, surface phase, and grain size were subsequently investigated using X-ray diffraction and scanning electron microscopy. The mechanical and wear resistance properties were determined using a Vickers microhardness tester, a microcomputer-controlled electronic universal testing machine, and a material surface multifunctional tester. Low-temperature degradation (LTD) was performed in an autoclave at 134 °C/0.2 MPa to evaluate the antidegradation properties. The results indicated that the sintered specimens were all t-ZrO2 at 1,500 °C, with the surface morphology exhibiting a high degree of denseness without the presence of cracks. The average grain size of the sintered specimens at 1,500 °C was 0.28–0.54 μm, whereas the best mechanical properties were obtained for the sample with a nano MgO content of 0.4 wt. %, with a relative density of 96%, a flexural strength of 660.13 MPa, and a Vickers hardness of 1,656.3 HV. The coefficient of friction was 0.15 and the mass wear rate was as low as 0.08 mg/Nm. No significant monoclinic phase was generated after 10 h of LTD, with the monoclinic phase content decreasing from 64.8% to 15.3% after 60 h.