Effect of pre-oxidation treatment on thermal shock resistance and residual stress of thermal barrier coating

The thermal barrier coating by taking MCrAlY as bonding coating and ZrO₂+8% Y₂O₃ as top coating were deposited on the nickel-based super-alloy by air plasma spraying. Pre-oxidation treatment was carried out on the thermal barrier coatings by controlling the oxygen pressure in high vacuum sintering furnace. Then,the effects of pre-oxidation treatment on the thermal shock resistance and residual stress were investigated, respectively. The results show that pre-oxidation treatment improves the density of bonding coating,which makes it uniform and reduces the probability of complex stress caused by convex point in interface area. Meanwhile,pre-oxidation treatment interferes the growth process of thermally grown oxide (TGO),reduces the TGO growth rate and the stress concentration of coating. Residual stress increases with the increasing of thermal cycles. However,pre-oxidation treatment can slow down the increasing rate of residual stress. The residual stress of 650.1 MPa can be reached after 350 thermal cycles without pre-oxidation, while the residual stress is only 492.5 MPa after 400 thermal cycles with pre-oxidation.