High-temperature oxidation behavior of HASTELLOY C-4 in steam

A commercial superalloy HASTELLOY C-4, was studied to evaluate its resistance to oxidation at elevated temperatures. Specimens were exposed to steam from 600degreesC to 1200degreesC for 1 - 400 hr. The reaction kinetics of oxidation were determined, and the morphology of the oxide scales was investigated by optical and scanning-electron microscopy. It was observed that C-4 exhibited excellent oxidation resistance at all temperatures under study. This behavior is due to the formation of a compact and adherent oxide. The oxides formed during oxidation were identified by X-ray diffraction. The oxides observed were mainly Cr2O3, NiCr2O4, NiCrMnO4, FeCr2O4 and (Cr, Fe)(2)O-3.