Thermal Shock Behavior of Y2O3-Partially Stabilized Zirconia

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Abstract
The thermal shock behavior of 3mol% Y2O3-partially stabilized zirconia with average grain size of 0.4μm (Z3Y-I) and 1.0μm (Z3Y-II) has been studied by the water quench method. Twenty three specimens of rectangular cross-section bar (3 by 3 by 45mm) were quenched at 300°, 350° and 400deg;C temperature differentials (ΔT) and their retained strength (σf) were plotted using the Weibull distribution function and doubly exponential distribution function. The retained strength distribution at ΔT=350°C are similar to the original strength distribution. On the other hand, the distribution at ΔT=350° and 400°C showed a shoulder at F=0.458 and 0.875, respectively, They are the initiation points of thermal shock damage, Assumming the surface heat transfer coefficient (h) of 0.19 and 0.4cal/cm2·°C·s, calculated stress intensity factors KI's for crack initiation by water quench were 73-75% and 91-92% of the critical stress intensity factor KIC for Z3 Y-I, and 69-70% and 86-88% for Z3 Y-II, respectively. A σf-δT curve for a certain failure probability level F showed instantaneous decline at a critical temperature differential δTc. High failure probability level F resulted in a high critical temperature diffrential δTc. Estimated δTc's are 310°, 360° and 400°C for F=0.2, 0.5 and 0.9, respectively.

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