High-Temperature Corrosion of Ti–46Al–6Nb–0.5W–0.5Cr–0.3Si–0.1C Alloy in N2/0.1%H2S Gas

Abstract

Ti–46Al–6Nb–0.5W–0.5Cr–0.3Si–0.1C alloy was corroded at 800–1100 °C for 200 h in N2/0.1%H2S gas to characterize its corrosion behavior in an aggressive H2S-containing environment. The alloy displayed superior corrosion resistance because Ti and Al preferentially reacted with impurity oxygen in the gas to form TiO2 and Al2O3. It corroded primarily by outward diffusion of Ti, Al, W, and Cr in addition to inward transport of sulfur, nitrogen, and oxygen. Scales were adherent and consisted of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (TiO2, Al2O3)-mixed layer. TiN and Ti2AlN formed at the scale/matrix interface where sulfur, Nb, W, and Cr segregated.