Pages 215-216
Thermal barrier coating (TBC) have been used in advanced gas turbine hot parts for improved performance. The failer TBC is induced by thermal stresses and shock due to the large formation of thermally grown oxide (TGO) at the interface between the YSZ top coat and MCrAlY bond coat. TGO is the mixed oxides layer consisting of the MCrAlY bond coat components such as Co, Ni, Cr and Al, formed by oxidation of bond coat and unmelted particles of the MCrAlY powders deposited in the plasma spraying. Thin film Cr2O3 overlay coating on MCrAlY bond coat is prepared using chromate treatment with chromic acid solution for control of oxidation growth rate of TGO at high temperature. TGO formed on chromate treated bond coat is composed of Al2O3 rich layer continuously and much more thermally stable. Chromate treatment process can be expected as an environmental barrier and oxidation rate control of MCrAly bond coat.
