Study of high-temperature oxidation of molybdenum-containing steels

The oxidation kinetics of the steels EI981A (10Kh16N25M6AF), R6M5, and 25Kh3M3BTsA was studied at 700, 800, and 1000 degrees C. The catastrophic oxidation (CO) was observed only at 1000 degrees C and only for the steels containing > 5% Mo. The stabilizing effect of tungsten on the Laves phase due to the formation of isomorphous solid solution was established. This effect does govern the oxidation rate of the steel, The effect of W (5.8%) surpasses the effect of chromium (up to 16%) and nickel (25%) in the steels. The CO mechanism observed in the present work coincide with that studied earlier. The X-ray diffraction analysis of the scale indicated that the main scale constituents are spinel and a rhombohedral phase.