Role of cerium addition in enhancing the oxidation resistance of austenitic Fe-Mn-Si-Cr-Ni shape memory stainless steels at 800 °C: Microstructure and oxidation mechanism. (December 2022) - Silva, R.
Abstract: Austenitic Fe-13.50Mn-3.98Si-9.54Cr-4.51Ni shape memory alloyed with (0.18, 0.42 and 0.96 wt%) Ce was exposed in air at 800 °C. Both 0.18 and 0.42 wt% Cerium additions yielded protective kinetics, while the 0.96 wt% Ce content did not change the oxidation resistance. Increased oxidation resistance was related to the growth of a fine-grained oxide layer, slightly wrinkled with a higher Cr content. Cerium also acted as a S scavenger, suppressing its interfacial segregation. In the Ce-free alloy, fast oxide growth occurred in regions where S segregated at the interface, leading to severe wrinkling of the layer, resulting in lower oxidation resistance. Highlights: Mn oxysulfide inclusions within FeMnSiCrNi contributed to poor oxidation resistance. Interfacial S segregation accelerated the scale growth, causing wrinkling of the oxide. Cerium acted as a S scavenger, suppressing its interfacial segregation. Small Cerium levels yielded protective oxidation kinetics. High cerium content did not positively affect the oxidation resistance.