Effects of bond coat preoxidation on the properties of ZrO sub 2 -8wt. % Y sub 2 O sub 3 /Ni-22Cr-10Al-1Y thermal-barrier coatings

Plasma-sprayed thermal barrier coatings (TBCs) consist of an intermediate MCrAlY bond coat to protect the substrate superalloy from oxidation/hot corrosion and a thermal insulating zirconia-based ceramic top coat. This system is developed for advanced turbine-engine, hot-section components. In this study the as-sprayed NI-22Cr-10Al-1Y bond coat was subjected to preoxidation treatment of 1,000C for 1, 50, 100, and 200 hr, also at 1,100C, 1,200C and 1,300C for 1 hr to form an oxide scale before subsequent deposition of a ZrO{sub 2}-8wt% Y{sub 2}O{sub 3} top coat. The oxidation kinetics were measured, and the phase constitution and morphology of pregrown oxides on the Ni-22Cr-1Y bond coat were analyzed by x-ray diffractometer and SEM/EDS to elucidate the improvement and degradation mechanisms of the new system. The results of the experiments in this study showed that the tentative ZrO{sub 2}-8wt.% Y{sub 2}O{sub 3} TBC specimens with preoxidized Ni-22Cr-10Al-1Y bond coat, when properly processed, exhibited lower oxidation rates and generally longer lifetime compared with traditional TBC specimens.