Impact strength properties of nickel-based refractory superalloys at normal and elevated temperatures

The dynamic yield and fracture stress of two refractory alloys were measured under shock-wave loading at normal and elevated (up to 680°C) temperatures. The tested materials were polycrystalline nickel-based superalloy Inconel IN738LC and PWA 1483 Ni-Co-Fe alloy in quasi-monocrystalline state. Both alloys are used as turbine blade materials for the hot first stages of gas turbines. The alloys exhibit non-monotonous dependence of the dynamic yield strength upon temperature with an abrupt increase in the temperature interval of 550-600°C. The dynamic tensile strength, in general, is less sensitive to temperature and shows less pronounced increase in the vicinity of 570°C. The observed anomalies of the dynamic strength properties correlate with anomalies in the heat capacity which are associated with the equilibrating of the short-range order in the γ-matrix of the alloys.