1986 Volume 94 Issue 1095 Pages 1142-1148
The theremal fatigue behavior of 3mol% Y2O3-containing tetragonal zirconia polycrystals (Y-TZP) with average grain sizes of 0.4μm (Z3Y-I) and 1.0μm (Z3Y-II) was studied by quenching into water bath at 20°C. The retained strength distribution of Z3Y-I subjected to multiple cycle quench at ΔT=350° and 300°C showed a shoulder at a certain F level, which corresponds to the initiation point of thermal shock damage. The F level increased with increasing thermal shock cycle number. For Z3Y-I at ΔT=350°, the proportion of damaged specimens was half for 1 cycle quenching and most for 10 cycles. At ΔT=300°C, the proportion of damaged specimens was none for 1 cycle, a few for 8 cycles and half for 60 cycles, but at 250°C, no crack was generated at 90 thermal shock cycles. On the other hdnd, the strength distribution of Z3Y-II subjected to multiple cycle quench at 350°C was similar to that of Z3Y-I at ΔT=350°C, but those of Z3Y-II at ΔT=300° and 250° Cwere followed by decreasing standard deviation, and the difference between maximum and minimum strengths was within about 3.1% for the thermal shock cycles above fifteen. The average strength of Z3Y-II subjected to 75 thermal shock cycles at ΔT=300°Cand 90 cycles at ΔT=250°C were about 60 and 76% of the original strength before water quench, respectively. The thickness of zone transformed from tetragonal to monoclinic phase by chemical reaction with hot water was 103μm for 30 thermal shock cycles, 155μm for 50 cycles and 356μm for 75 cycles at ΔT=300°C, and 36μm for 60 cycles and 211μm for 90 cycles at ΔT=250°C.
