Non-isothermal creep behavior of a second generation ni-based single crystal superalloy: Experimental characterization and modeling

Abstract

In order to simulate emergency regimes possibly encountered by turboshaft engines for helicopter, non-isothermal creep behavior of the second generation single crystal Ni-Based superalloy MC2 was investigated. These tests were performed with one short overheating at 1200°C during the isothermal creep life of the material at 1050°C Overheatings were carried out using a burner rig designed to achieve temperature jumps as fast as 60°C/s in the range 1050°C-1200°C Both the overheating duration and its position during the isothermal creep life at 1050°C of the material have a great effect on the non-isothermal creep behavior. The modifications in creep behavior were clearly linked with microstructural evolutions occurring during temperature changes, e.g: the dissolution of the γ' phase on heating the material and the dislocation recovery processes. Based on these microstructure characterizations, a classical macroscopic model involving isotropic variables and a von Mises criterion was enhanced with the addition of new internal variables representative of the γ'-volume fraction and a recovery function attesting for the dislocation activity.