The Cr-Mo steels, whose microstructure was tempered martensite, were oxidized isothermally at temperatures of 800-1000 degrees C for up to 30 h in air, and their oxidation behavior was examined. The thick scales that formed consisted mainly of Fe2O3. The scale spalled easily, owing to the formation of voids and cracks inside the scale. The oxides of Cr and Mo tended to be formed below the outwardly growing iron oxide scales.

Keywords: steel; oxidation; chromium; molybdenum