High temperature oxidation of heat-resistant alloys is considerably accelerated in the presence of
water vapor which can severely reduce the longevity of high temperature components. The purpose of
this study was to assess and compare the oxidation resistance of several Ni-Cr, Ni-Cr-Fe alloys, and Fe-
Cr-Ni austenitic stainless steels in humidified air. The laboratory test program included 1,008 hour
oxidation exposures at 649oC, 760oC and 871oC in air + 5 vol. % H2O and air + 10 vol. % H2O. Alloy
performances were ranked by assessing weight change and extent of attack which includes metal loss,
average internal penetration, and maximum internal penetration. The average and maximum internal
penetrations were measured using optical microscopy. It was found that the Ni-based alumina-forming
alloy exhibited superior performance compared to the other alloys selected in the study. Among
chromia-formers, Fe-based alloys were found to be more susceptible to increased degradation in
humidified air.
Keywords: Ni-Cr alloys, Ni-Cr-Fe alloys, Fe-Cr-Ni alloys, oxidation resistance, water vapor, chromiaand
alumina-formers