5th International High Manganese Steel Conference - HMNS 2022

The influence of La additions on the microstructure and high temperature oxidation of austenitic steels Fe-20-25Mn-10-12Al-1C (wt.-%) has been investigated. Three different alloys were produced from commercially pure metals by an arc furnace with a water-cooled copper hearth and a non-consumable tungsten electrode. The melting was performed in an Ar atmosphere (99.98% purity) additionally purified by a Ti melt. The cast alloy microstructures of before and after high temperature oxidation at 700-900°C were studied using SEM/EDX and EBSD analyses. The phase composition of steels and oxide scale was determined by X-ray diffraction. It was shown that the modification of the melt with small lanthanum additions (0.1-0.5 wt.-%), not only refines the austenite and kappa-carbide (Fe, Mn)3AlC grains during crystallization but also increases the oxidation resistance of steel. The uniform dense oxide film formation mainly consisted of Al2O3 on the alloy/oxide scale interface, which better prevents the further diffusion of oxygen into the steel and protects it. The cast advanced steels Fe-25Mn-11Al-0.92C have ultimate tensile strength (UTS) more than 1 GPa and high oxidation resistance at the same time.