High temperature thermal diffusivity of nickel-based superalloys and intermetallic compounds

Abstract
By means of an installation developed in our laboratory, we measured the thermal diffusivity (α) as a function of temperature for several single and polycrystal nickel-based superalloys as well as for different intermetallic compounds with a L1₂ (Ni₃Al, Ni₃Si, Ni₃Ge, Ni₃Fe, Zr₃Al, Co₃Ti), L1₀ (TiAl) or B2 (NiAl) structure. In the case of nickel-based superalloys, the experiments pointed out an unexpected but reproductible slope change in the α=f(T) curves at about 750°C, which is not explained at this time. It was shown that the initial microstructure, the crystal orientation and the grain size seem to have no noticeable influence on the thermal behaviour. Slight variations between different alloys were rather attributed to a chemical composition effect. In the case of intermetallic compounds the temperature dependence of the thermal diffusivity appeared to drastically change from an alloy to an other. Thus, no clear relation could be found between thermal behaviour, crystallographic structure and strength temperature dependence of these alloys.