Enhancing oxidation resistance of a novel nickel-saving dual-phase heat-resistant cast steel based on Mn-N optimized oxide scale

The effect of Mn-N on the oxidation behavior and microstructure evolution of a novel nickel-saving Fe-26Cr-4Ni-0.3C dual -phase heat-resistant cast steel at 900 degrees C was investigated. After 100 h of oxidation, the H-Mn-N steel (3.14 %Mn -0.232 %N) exhibited approximately three times better oxidation resistance compared to the L -Mn -N steel (0.24 %Mn -0.084 %N). The increase of Mn-N decreased the oxidation rate from 2.30 x 10(-2) mg(2) center dot cm (-4) center dot h(-1) to 3.26 x 10(-3) mg(2) center dot cm (-4) center dot h(-1). The oxide scale structure of L -Mn -N steel consisted of outer Cr2O3, inner (Fe0.6Cr0.4)(2)O-3, and (FeCrO4)-Cr-1.4-O-1.6, while the oxide scale of H-Mn-N steel (3.14 % Mn) was SiO2, MnCr2O4, and Mn1.5CrO4 from the matrix to the outside. Mn-N increased the proportion of austenite from 40 % to 70 %, which reduced the diffusion rate of oxygen. This hindered the formation of layered oxide Cr2O3 and promoted the formation of a dense layer of SiO2 on the matrix surface, providing a pathway for the enhancement of the trade -off between oxidation resistance and cost.