Effect of thermal exposure on hardness and Young's modulus of EB-PVD yttria-partially-stabilized zirconia thermal barrier coatings

The effect of thermal exposure on hardness and Young's modulus of 4.0 mol% Y2O3-partially-stabilized ZrO2 coating material deposited by an electron beam physical vapor deposition has been investigated after exposure at 1200 °C and 1400 °C in air for up to 100 h, using an ultra-micro-indentation technique. The indentation tests were carried out with loading rate of 0.88 mN/s and holding time of 20 s at the maximum load of 50 mN. Before and after thermal exposure, the microstructure of the coating was characterized using scanning electron microscopy. Before thermal exposure, the coating showed a typical columnar structure. After thermal exposure, however, the columnar structure degraded and the degradation depended on exposure temperature and time. The hardness and Young's modulus were higher on the plan-section than on the cross-section before and after thermal exposure. The hardness and Young's modulus on both sections significantly increased after thermal exposure. The increases depended on exposure temperature and time, as a result of the sintering effect.