Static and dynamic aspects of coupling between creep behavior and oxidation on MC2 single crystal superalloy at 1150 °C

Creep tests were performed on thin wall specimens made of MC2 single crystal superalloy at 1150 °C and under controlled atmosphere. The results highlight the deleterious oxidation effect on creep properties. The assumption that oxidation leads to a non-load-bearing affected zone is insufficient to explain the difference in creep rate that was noticed between tests performed under synthetic air and under hydrogenated argon, and cannot explain the decrease of the strain rate during the tests that were carried out with a change of atmosphere from synthetic air to hydrogenated argon. On the other hand, these experimental results are consistent with vacancy injection due to partial cationic oxidation, which accelerates the creep rate by promoting creep mechanisms controlled by diffusion. The anionic protective alumina scale formed under hydrogenated argon prevents this vacancy flux. The integration of this dynamic and long range oxidation effect in creep strain models is discussed.