Excellent High‐Temperature Oxidation Resistance of a 9Cr–6W–0.3N Heat‐Resistant Martensitic Steel

Since novel 9Cr–6W–0.3N high‐nitrogen heat‐resistant martensitic steel (HNHM) with high corrosion resistance was designed and developed, its high‐temperature oxidation resistance becomes one of important concerns. In this article, the oxidation behavior of HNHM, comparing with MarBN and CB2 steels, is investigated at 650–850 °C, and a comparative study of oxidation kinetics is conducted. The results demonstrate that the HNHM displayed superior oxidation resistance to CB2 and MarBN, which is attributed to the synergistic effect of high W and N contents that promoted Cr 2 O 3 ‐rich oxide layer formation, leading to the formation of a more dense oxide layer. At elevated temperatures, HNHM forms three‐layer structure: Fe‐rich oxide layer (Fe 2 O 3 and Fe 3 O 4 ), spinel oxide layer ((Fe, Mn)Cr 2 O 4 ), and Cr‐rich oxide layer (Cr 2 O 3 ). Accordingly, CB2 forms a less dense three‐layer structure similar to that of HNHM and MarBN forms an additional Fe‐rich oxide layer on the Fe‐Cr oxide layer.