Modelling creep of single crystal CM186LC alloy under constant and variable loading

This paper investigates the creep behaviour of 〈0 0 1〉 oriented single crystal (SX) alloy CM186LC, a nickel base superalloy for gas turbine directionally solidified blade applications. At the explored temperatures of 800 and 900 °C and at stresses relevant to service, the creep curves of this class of alloys are dominated by a long accelerating “tertiary” stage. This stage was modelled through a damage parameter being proportional, as a first approximation, to the creep strain. The proposed differential equations can interpolate the constant load tests and they also show a natural capability to predict the effect of step changes in load and temperature on the creep behaviour of the alloy, without appealing to arbitrary strain or time hardening rules.