2005 Volume 46 Issue 8 Pages 1882-1889
As Hastelloy-XR alloy is a candidate structural material for the IS (Iodine-Sulfur) process in hydrogen production, oxidation and sulfidation of Hastelloy-XR alloy in Ar–O2 and Ar–SO2 atmospheres were studied by thermogravimetry at temperatures from 1000 to 1300 K. In Ar–O2 atmosphere, the mass change obeyed a linear-parabolic law at oxygen partial pressures (PO2) from 0.01 to 10 kPa. The oxidation scales consisted of inner Cr2O3 layer and outer Mn1.5Cr1.5O4 spinel layer. The surface morphology of the oxide scales changed from island-like to buckled and to porous texture with decreasing PO2. In Ar–SO2 atmosphere, the mass change obeyed a linear-parabolic law at SO2 partial pressures (PSO2) from 0.05 to 5 kPa. The morphology of corrosion scales changed mainly with corrosion temperature. While oxidation was dominant at 1073 and 1173 K forming double-layer scales of inner Cr2O3 and outer Mn1.5Cr1.5O4 spinel, sulfidation was accompanied with oxidation at 1273 K and PSO2<0.5 kPa with scales consisting of Fe3O4, FeCr2O4 and Cr2O3 layers and Ni3S2 dispersed particles together with CrS particles segregating at the grain boundary of Hastelloy-XR alloy.