Oxidation Behavior of HVAF-Sprayed NiCoCrAlY Coating in H-2-H2O Environment

Isothermal oxidation behavior of an HVAF-sprayed NiCoCrAlY coating on AISI 304L was studied in an Ar-10 %H-2-20 %H2O environment at 600 A degrees C. Techniques such as BIB/SEM, EDS, and XRD were used to comprehensively characterize the coating and the coating/substrate interface to investigate the oxidation mechanisms. Results were also compared with those obtained from an uncoated AISI 304L substrate. The alumina-forming NiCoCrAlY coating was found to exhibit superior oxidation behavior due to the formation of a slow-growing and protective Al2O3 scale, while the chromia-forming bare 304L substrate lost its protective capability due to the formation of a duplex [Fe3O4 on (Fe,Cr)(3)O-4 spinel oxide] corrosion product layer