Effect of hydrogen on oxidation of Fe-20Cr-(1Si, 2Mn or 2Al) alloys in water vapour at 650 °C

Hydrogen production and utilisation involve H 2 O(g) at high temperatures. However, the effect of hydrogen on chromia-forming heat resistant alloys in H 2 O is still unclear. In this work, Fe-20Cr and Fe-20Cr-(1Si, 2Mn or 2Al) (wt%) were exposed in Ar-xH 2 -10H 2 O gases (x = 2, 10 and 20 vol%) at 650°C for up to 310 h. The binary alloy experienced breakaway oxidation in all gases. Increasing hydrogen content reduced corrosion rates and altered oxide morphologies. Adding Mn, Al or Si to the alloy suppressed oxidation to some extent. The effects of both hydrogen and alloying on the diffusion processes supporting oxidation are discussed. • Increasing H 2 concentration reduced oxidation rate and altered oxide morphology. • High concentration of H 2 in reaction gas led to the embrittlement of outer iron oxide. • The presence of H 2 enhanced oxygen permeability, forming a thicker IOZ. • Si, Al or Mn additions improved the oxidation resistance of Fe-20Cr in water vapour.