Oxidation behaviour of austenitic stainless steel 304HCu in Advanced Ultra Supercritical (AUSC) steam and the efficacy of shot-peening treatment.

Effect of shot-peening on the oxidation behaviour of alloy 304HCu in controlled advanced ultra-supercritical (AUSC) steam at 650 ◦C, 31 MPa for 600 h was investigated. Non-shot peened surfaces form thick Fe-rich oxides, undergo internal oxidation, and suffer oxide spallation sooner than those reported in literature. Shot-peened surfaces form a thin, external chromia scale with Mn(Cr,Fe) 2 O 4 and MnCr 2 O 4 spinels growing above and below it respectively. Shot-peening enhances Cr and Mn diffusivity through grain refinement and increased dislocation density, which aids in resisting chromia scale breakdown, eliminating iron oxides, and preventing oxide spallation. Oxide growth mechanism in AUSC steam is discussed. [Display omitted] • Alloy 304HCu was oxidized in AUSC steam at 650 ℃, 31 MPa for 600 hours. • Non-shot peened surfaces form thick Fe-rich oxides and undergo internal oxidation. • AUSC steam causes severe oxidation and early onset of oxide spallation. • Shot-peening resulted in grain refinement and high dislocation density. • Shot-peened surfaces resist Cr 2 O 3 breakdown, form thin, external Cr & Mn-rich oxides. [ABSTRACT FROM AUTHOR]