High-temperature oxidation behavior and subsurface phase transformation of high-Mn high-Al steel

Abstract

High-Mn steels are widely used in engineering applications because of their high strength, high hardness, and excellent toughness. In the industrial production of high-Mn steel, the steel is easy to be oxidized during the homogenization process, which may affect the properties of high-Mn steel. In this work, high-Mn high-Al steel with composition of (25–32)wt-%Mn-(8–11)wt-%Al-1wt-%C-Fe was prepared, the oxidation behavior and subsurface phase transformation of steel at 800 °C–1200 °C were investigated by thermogravimetric analysis, scanning electron microscope and X-ray diffraction. The results show that the curve of oxidation weight gain with time is in good agreement with linear equations below 900 °C, which obey the parabolic rate law in the temperature range of 1000 °C–1200 °C. The steel matrix would be covered by the oxide scale earlier at higher temperatures, which decreases the oxidation reaction rate and makes the turning point of the oxidation reaction rate reach faster at higher temperatures. The Mn-depleted zone resulting from the selective oxidation of Mn is formed in the steel matrix epidermis, leading to the subsurface phase transformation, which may deteriorate the steel properties.