Sanicro 25 in advanced ultra-supercritical (AUSC) steam: Oxidation behaviour of a high strength, heat-resistant austenitic stainless steel for high-efficiency coal-fired power plants

The oxidation behaviour of Sanicro 25 was investigated in advanced ultra-supercritical (AUSC) steam at 650–710 ℃, 31 MPa for 600 h. The alloy recorded low weight gains and formed sub-micron-sized external oxide comprising (Mn,Fe,Ni)Cr 2 O 4 spinel over Cr 2 O 3 . Its oxidation resistance was better than other candidate heat-resistant stainless steels and on par with Ni-base superalloy 617. Fine strengthening precipitates of Cu, Cr-rich M 23 C 6 , W-rich Lave’s and Nb-rich Z phases were found to form in the substrate during oxidation and their volume fraction increased with increasing temperature. The reasons for the alloy’s superior AUSC steam oxidation behaviour and its implications are discussed. • Sanicro 25 was oxidised in AUSC steam at 650 & 710 ℃, 31 MPa for 600 h • Oxidation resistance better than alloys 310S, HR3C & similar to that of alloy 617. • Sub-micron sized oxides comprising an (Mn,Fe,Ni)Cr 2 O 4 spinel over Cr 2 O 3 were observed. • Several stable nano-precipitates form in the matrix. • Results augur well for the usage of Sanicro 25 at T > 650 ℃ in AUSC power plants.