Abstract
The nickel based superalloy MC2 is made of an austenitic matrix gamma strengthened by ordered intermetallics precipitates gamma'. This alloy is widely used for high temperature applications such as turbine blades. Two different aspects of its very high temperature creep behaviour are studied. Firstly a modification of the anisothermal creep behaviour with an increase of the creep rate and a decrease of the time to rupture, and secondly, a directional coarsening oriented 45° away from the load axis. Isothermal and anisothermal creep tests were performed at 1150°C, 1100°C and 950°C and compared to finite elements simulations. Resulting microstructures were observed by means of scanning and transmission electron microscopy. We suggest mechanisms based on the dissolution of the gamma' rafts, the climbing of dislocations and exchange of vacancies.