As-cast microstructure, room temperature hardness and high temperature creep deformation of an equimolar quaternary CoNiFeCr alloy and of two slightly modified versions
Résumé
The equimolar CoNiFeCr composition can be considered as a Mn-free Cantor alloy. Removing manganese allowed improving significantly its hot oxidation resistance in air, even for temperatures up to 1100°C. Another beneficial consequence of Mn suppression is potentially a much better creep-resistance, which is also expected to increase with addition of Ti and Ta. This is what was explored in this work. After microstructure and hardness control by electron microscopy and Vickers indentation (load: 1kg), flexural creep tests were carried out at 1100°C for a centered 3 points bending solicitation under constant load inducing locally 10 MPa as maximal tensile stress. The CoNiFeCr alloy and its version containing Ti are single-phased while a second phase rich in tantalum is present in the Ta-containing one. Concerning the creep behavior, the CoNiFeCr alloy deformed much slower than the Cantor alloys. The versions alloyed with Ti and Ta resisted creep better than the former alloy. The Ta-containing CoNiFeCr alloy demonstrated the best resistance, with a particularly slow deformation.
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