Effects of precipitation on the scale and grain growth in 9% Cr tempered martensite steel upon steam oxidation

Abstract We compare the effects of long-term steam oxidation behavior in two commercial 9% Cr tempered martensite steels with (T92) and without (T91) tungsten at 600–700 °C up to 20,000 h. Microstructural investigations reveal abnormal grain and oxide scale growth after decomposition of Cr23C6 via oxidation in T91, while the tungsten-rich Laves phase in T92 restricts grain growth and assists the formation of a continuous chromite oxide scale. The findings suggest how formation of Laves phase aids oxidation resistance in heat resistant steels.