EFFECT OF BOND-COAT PRE-ALUMINIZATION AND PREOXIDATION DUPLEX PRETREATMENT ON THE PERFORMANCE OF ZRO2-8 WT-PERCENT Y2O3/CO-29CR-6AL-1Y THERMAL-BARRIER COATINGS

A modification to the conventional thermal-barrier coating (TBC) system was made. In this study, the low-pressure, plasma-sprayed Co-29Cr-6Al-1Y bond coat received a duplex pretreatment of bond-coat pre-aluminizing and pre-oxidation prior to overlaying the air-plasma sprayed ZrO2-8 wt.% Y2O3 top coat. The effects of this treatment on the properties of the TBC system were evaluated by thermal-cyclic test at 1050-degrees-C in air. The results of cyclic-oxidation tests showed that the proposed processes could remarkably improve the performance Of ZrO2-8 wt.% Y2O3/Co-29Cr-6Al-1Y TBC. The improvement was attributed to a modification of bond-coat oxides and the associated reduction of the oxidation rate of the MCrAlY bond coat.