A high temperature deformation mechanism map for the high performance Ni-base superalloy GTD-111

GTD-111, used for gas turbine first stage blades, is a new, high performance and less investigated Ni-based superalloy. This alloy, with high volume fraction of γ′ phase, has excellent creep resistance. It is believed that several creep deformation mechanisms operate at various combinations of temperature and stress. The regions of the controlling mechanisms can be described in terms of a stress-temperature deformation mechanism map. To construct a creep mechanism map for GTD-111 superalloy, single-specimen creep tests at constant stress/variable temperature and constant temperature/variable stress were conducted. The map consists of two separate dislocation controlling mechanism fields; a stacking fault and anti-phase boundary region, and a dislocation climb region. Also, it was clear that a diffusional creep mechanism operated at lower stresses. Microstructural analysis using TEM on creep tested specimens in the two dislocation creep fields confirmed the deformation mechanism map for GTD-111 superalloy.