The High Temperature Oxidation Behavior of CoNiCrAlY Bond Coating with Alumina Layer Deposited by EB-PVD Method

The thermally grown oxide (TGO) growth between bond coating and ceramic top coating during high temperature operation causes the spallation of thermal barrier coating (TBC). To improve the oxidation resistance of bond coating, a thin alumina layer was forwed by electron beam physical vapor deposition (EB-PVD) method. The microstructure and the high temperature oxidation behavior were investigated. The EB-PVD alumina layer on CoNiCrAlY bond coating showed an amorphous structure, and the alumina layer was transformed to an alpha alumina after heat treatment at 1323 K for 7.2 ks. During the high temperature oxidation test in air at 1373 K, the TGO growth on the CoNiCrAlY bond coating was suppressed by the application of alpha alumina layer. The existence of yttria stabilized zirconia (YSZ) top coating did not affect on the oxidation rate of the bond coating. The oxidation rate suppression by alumina layer deposition was also performed on the TBC specimen.