As in classical superalloys based on nickel or cobalt, MC carbides can be easily obtained in cast high entropy alloys (HEA) for enhancing their mechanical properties at high temperatures. These carbides may have also some influence on the hot oxidation properties. They can be also not neutral for the oxidation behavior. To explore their possible influence in this field, an equimolar CoNiFeMnCr reference alloy and two versions containing TaC or HfC carbides were prepared by casting and exposed to air at 1000°C. Their oxidation behaviors were studied by characterizing the obtained corrosion products and the modifications induced in the subsurfaces of the samples. Results show that TaC and HfC are moderately involved in the oxidation phenomena but they obviously influence the Cr and Mn diffusion toward the oxidation front. This seemingly aggravates more the already poor oxidation high temperature resistance of the base alloy. However the harmful effect of the TaC seems to be much lower than the one of the HfC, and the TaC–strengthened CoNiFeMnCr alloy is only a little less resistant against oxidation than the carbide–free reference equimolar alloy.


High entropy alloys, Tantalum monocarbides, Hafnium monocarbides, High temperature exposure to air, Metallographic characterization, Hf-doping, Oxidation kinetic assessment,


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