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 degrees C and 1400 degrees 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 20s 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 I 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. (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.