Fabrication Of ZrO₂ Ceramics By Pressless Sintering And Its Wear Properties

In this papers, the powder, which contains 2mol% Y₂O₃ and possesses an average size of 0.65μm were formed with Cold Isostatic Press and the green compacts were sintered into ceramics presslessly. The effects of molding press and sintering temperature on the mechanical properties of ZrO₂ ceramic were investigated by some mechanical methods such as SENB and Three Points Bending and so on, and some testing methods such as XRD and SEM were studied. The relationship between the mechanical properties and microstructure was also analyzed. Meanwhile, the effect of molding press on the wear property was also discussed. The powders were formed with Cold Isostatic Press at the pressure of 150 MPa, 200MPa and 250 MPa respectively, and then were made into ZrO₂ ceramic through 1 hour's sintering at a normal pressure and a temperature of 1500℃. The results of Three Points Bending test indicate ZrO₂ ceramic can get favorable mechanical properties when the forming pressure is 150 MPa. The Bending Strength and the Fracture Toughness are 848MPa and 12.5 MPa·m^1/2 respectively. The relative density decreases with the increase of molding press. The lower relative density lead to the growth of porosity, and then results in the decrease of effective loading area and the Bending Strength. The green compacts formed with Cold Isostatic Press at the pressure of 200MPa were sintered ceramic at 1400℃, 1450℃,1500℃and 1550℃for 1 hour. The results indicate that ZrO₂ ceramic sintered at 1500℃can get favorable mechanical properties. The Bending Strength and the Fracture Toughness are 711MPa and 12.46 MPa·m^1/2 respectively. The analysis shows the free path among particles and the porosity of the compacts decrease with the ascending of sintering temperature, which is favorable to the sintering and densification. However, with the further increase of sintering temperature, the grain size exceeded the critical size of phase transformation and then got some monoclinic phase ZrO2, which decreased the bulk density of the samples. The results of the water-surrounding rubbing wear experiments on the ZrO2 ceramics with various molding press indicate that the compact with a molding press of 150 MPa possesses a low wear rate and a favorable abrasive wear resistance. The high density of the sample with this molding press, the great transformation of tetra-and mono-ZrO2 and the little internal stress of the sintered compacts may be the factors that make the compact get a low wear rate.