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High temperature oxidation of iron-based alloys reinforced by hafnium carbides. Part 1: Thermogravimetry results

Elodie Conrath, Patrice Berthod

Athird family of chromium-rich alloys containing interdendriticHfCcarbides for their mechanical resistance at high temperatures, based on iron, was studied in oxidation at high temperature by thermogravimetry. One considered separately the oxidation kinetic during heating, during the isothermal stage and during cooling. Three quaternary alloys, containing 25wt.%Cr, 0.25 to 0.50wt.%C, and 3.72 to 5.58wt.%Hf,were subjected to the same thermal cycle as previously done for similar HfC-containing nickelbased and cobalt-based alloys. Here too the oxidation start temperature at heating, total mass gain during heating, isothermal mass gain, temperature of spallation start at cooling were especially examined, with comparison with ternary Fe-25C-0.25C and 0.50C alloy, to specify the possible effects of the carbon content and of the presence of hafnium and of its content. Globally the oxidation behaviour of the HfC-containing iron-based alloys was good, at the level of the corresponding nickel-based alloys. Notably, isothermal mass gain kinetic was rather slow and a significantly improved resistance against oxide spallation was observed for the alloys containing HfC carbides. These results were thereafter compared with the similar ones previously obtained for the corresponding HfC-containing cobalt-based and nickel-based alloys.