Development of a New Single Crystal Superalloy for Industrial Gas Turbines

In order to raise the turbine inlet gas temperature to improve thermal efficiency of gas turbines, turbine blade and vane materials are required to have high creep rupture strengths. In the present study, a new single crystal superalloy with a moderate Re addition (2.4wt%) has been developed. The alloy shows a higher creep rupture strength than the second and even the third generation single crystal superalloys. The composition of the developed single crystal superalloys were designed with a computer aided alloy design program which was developed in National Research Institute for Metals (NRIM-ADP) and finally one alloy was selected experimentally. The developed single crystal superalloy had a stress rupture temperature advantage over 30°C in comparison with the second generation single crystal superalloys at the 137MPa/105hours condition. The developed alloy has a large negative lattice misfit. The large negative lattice misfit enhances the formation of continuous y’ platelets, the so-called raft structure, and a tine interfacial dislocation network during creep tests. These are considered to prevent the movement of dislocations and thus decrease the creep strain rate.