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

Elodie Conrath, Patrice Berthod

Hafnium, element known to be especially active in oxidation at high temperature, was added in high quantities to model chromium-rich carboncontaining nickel-based alloys, in order to promote the formation of hafnium carbides preferentially to chromium carbides. As earlier seen for cobaltbased alloys displaying such hafnium contents, hafnium effectively favoured the formation of interdendritic HfCcarbides and then led to special nickel-based alloys the behaviour in oxidation at high temperature of which was then studied. This was done in artificial dry air at 1200°C during 46 hours after a heating phase and before a cooling phase which were both also characterized: in terms of temperature start and thereafter rate of oxidation during heating, and of oxide spallation temperature start and amplitude of mass loss during cooling. Some of the obtained results were conform with what was observed for Hf-free and Hf-containing cobaltbased alloys for almost the same oxidation cycle, such as lower temperatures of oxidation start at heating and of oxide spallation at cooling, but differences were also noticed and are here described.