Studies On The Friction And Wear Of Y-TZP Matrix Ceramic Materials

On the basis of the application of the ceramic cylinder liners, the friction and wear of Y-TZP matrix ceramic materials were investigated systemically.The wear rates of 3Y-TZP ceramics mated with (Mg,Y)-PSZ were concerned with both the normal load and the sliding speed under dry sliding, but were mainly related to normal load with the water lubrication. And the wear rates of 3Y-TZP ceramics with the water lubrication were lower than that of dry sliding. With the increase of the sliding speed and the normal load and with the prolonged sliding time, the surface temperature was elevated. The wear of 3Y-TZP ceramics was accelerated due to the elevated temperature of the wear surfaces.The wear resistance of 3Y-TZP ceramics was effectively improved due to the dispersed Al2O3 particles because of the improvement of the mechanical properties of the ceramics. With the increase of the normal load, the wear rates of ADZ ceramics were increased. Under low and medium normal load (100N and 300N), the wear resistance was controlled by the hardness of ceramics, and under high normal load (500N) the martensitic transformation toughening was obviously contributed to the wear resistance of the ceramics. Although the hardness and the fracture toughness of two 10ADZ ceramics, which difference between them was the adding method of yttria (i. e. co-precipitated and mixed), were close, the wear resistance of the former was better than that of the latter which arisen from the uniform microstructure of the former ADZ ceramic. The experiment results showed that the worn surfaces of ADZ ceramics were of fractal characteristic, and the larger the normal load, the higher the fractals dimension and the wear rate, which indicated that there were close relation between the surface properties and the tribological properties of the ceramics. The studies showed that the increase of the wear rate of Y-TZP matrix ceramic materials was not monotonously with increasing grain size. For t-ZrO2 particles the martensitic phase transformation occurred under the action of frictional stress and the phase transformation toughening made for enhancing the wear resistance of the ceramics. There was the critical grain size for the phase transformation, that is, when the grain size of t-ZrO2 particles was too small to cause the phase transformation beneficial of which wear resistance. When the grain size was so big that the phase transformation was prone to occur which brought a lot of microcracks and these cracks intersected to easily result in the fracture that lowered the wear resistance of ceramics. Therefore, the conception was brought forward that the relationship between the wear resistance and the grain size of zirconia ceramics could not be simply expressed in the form W-1∝G-1/2. The porosity displayed little influence on the friction coefficient of 10ADZ ceramics, but the wear resistance was decreased with the increase of the porosity. The idea of critical pore size was put forward, namely, the pore whose size was smaller than the critical size had hardly effect on the wear of ceramics. Both the open and close porosity had negative influence on the wear resistance of ceramics. The studies on the effects of abrasive particle on ADZ ceramics indicated that the sharp and hard abrasive particles lowered the wear resistance.It was firstly studied that the wear resistance was enhanced by dispersed appropriate mullite to Y-TZP ceramics (MDZ). The main effects of rod-like mullite on the improvement of the wear resistance were as follows: ⑴ Restraining the propagation of the preexisted cracks and bridging toughening to absorb more energy needed for the propagation of microcracks; ⑵Restraining the slippage of the grain boundary; ⑶ Reducing the mean grain size and densifing the ceramics. The main wear mechanism of MDZ ceramics was microploughing, plastic deformation and pull-out of mullite grain.Combining the results of the experiment with the applied condition of the field, the theoretic service life was obtained, and the ratio of theoretic service...