Effect of Co vs. Fe content on early stages of oxidation of Co-Cr-Fe-Mn-Ni-Si complex concentrated alloys at 800 °C
Jonathan Apell, Robert Wonneberger, Hartmut Stöcker, Pauline Meye, Katharina Freiberg, Martin Seyring, Stephanie Lippmann, Andreas Undisz
Abstract
The effect of Co vs. Fe content on early stages of oxidation in air was studied in Co-Cr-Fe-Mn-Ni-Si complex concentrated alloys (CCAs). A higher Co content decreased the phase fraction of protective corundum-type oxide as determined quantitatively. This is consistent with presented thermodynamic calculations, predicting a decrease in Cr activity with increasing Co content. The formation of Cr-rich corundum-type oxide is hindered in favor of Fe/Co/Ni-rich spinel-type oxide. Accordingly, beneficial effects of Co on mechanical properties of 3d transition metal CCAs for high temperature applications need to be balanced with detrimental effects on oxidation resistance.