Behavior in Cooling-Induced Oxide Scale Spallation of Original and Modified Cantor’s HEA Alloys Oxidized at High Temperature

Cast Cantor’s alloys, and derivatives issued from Mn and Cr Contents modifications and/or MC (TaC and HfC) carbides in situ formation, suffer more or less from oxide spallation at cooling. To investigate the dependence of this phenomenon on the alloy chemical composition and on the single-phased or double-phased state of the alloys, several alloys were first exposed to isothermal oxidation, and second to cooling down to room temperatureTemperature with mass variation recording. The differences between the isothermal oxidation temperatureTemperature and the temperatureTemperature of mass loss start, the sequences of the following steps of spallation and the final spallation-induced mass loss were analyzed as functions of the chemical and microstructural characteristics of the alloys. This evidenced the influences, on oxide spallation at cooling, of the Cr/Mn ratio and of the presence or not of the MC carbidesMC carbides. These observations led to recommendations for thermal cyclingThermal cycling conditions in service.