Tensile behavior of single crystal nickel-based superalloys at 650°C

The yield strength (YS) of single crystal Ni-based superalloys is a critical factor for low temperature low cycle fatigue and Out-of-phase thermomechanical fatigue durability of turbine blades. The chemical composition of this class of alloys appears to have a major role in their low temperature tensile behavior. Indeed, alloying el-ements modify the antiphase boundary (APB) energy of the & gamma;& PRIME; phase and so its resistance to shearing. To investigate the influence of the chemical composition on the YS, 18 superalloys of different generations were tensile tested at 650 & DEG;C. The results show a significant YS evolution of up to 250 MPa between the first generation and the following generations. The YS differences are mainly attributed to the contributions of & gamma;' which in turn is dependent on the & gamma;' phase composition. An EDNNB model was adapted to estimate the APB energies for the aforementioned set of alloys using Thermo-Calc data. Ta and Ti elements appear to be the most efficient & gamma;& PRIME; strengtheners. The higher their content is, the higher the APB energy is and the stronger the alloy is in terms of tensile YS. Several alloys also exhibit an important strain hardening.