The influence of temperature gradient across YSZ on thermal cyclic lifetime of plasma-sprayed thermal barrier coatings

The influence of the temperature gradient within plasma-sprayed yttria-stabilized zirconia (YSZ) on the thermal cyclic lifetime of thermal barrier coatings (TBCs) was investigated via gradient thermal cycling test and theoretical model. YSZ surface was heated to the peak temperature in 70 s, then kept for a dwell time of 50 s at the peak temperature and cooled down to 100 °C in 120 s. YSZ surface temperatures were set to be 1150 °C, 1200 °C and 1250 °C, corresponding to temperature differences of 150 °C, 200 °C and 250 °C across 250 µm thick YSZ coating, respectively. A theoretical model is introduced to describe the correlation between thermal cyclic lifetime and temperature gradient. Experimental results show that the temperature gradient has a remarkable impact on the thermal cyclic lifetime of TBCs, which decreases with increasing temperature gradient. The theoretical model reveals that thermal cyclic lifetime of TBCs decreases with the increase of the temperature gradient following a power function, which reasonably agrees with the experimental results. Moreover, it was found that the temperature gradient has little effect on the cracking mode of the TBCs because the stress distribution characteristics in TBCs subjected to thermal cycling with different temperature gradients remain unchanged based on the numerical simulation results.