The effects of different alloying elements on the thermal expansion coefficients, lattice constants and misfit of nickel-based superalloys investigated by X-ray diffraction

Abstract

The influence of variations of the chemical composition, especially by adding refractory elements, on the lattice parameter and thermal expansion coefficients of nickel-based superalloys was investigated. To analyse these effects in a systematic way, measurements in a series of experimental and commercial alloys with different alloy compositions were performed. The lattice constants of the γ and γ′ phases were measured by X-ray diffraction at temperatures between 25°C and 1100°C. The main focus was on the effects of rhenium additions, but alloy compositions containing ruthenium and iridium were also included. It was possible to interpret the changes of the lattice parameters of γ and γ′ as effects of certain alloying elements by analysing the local chemical composition of the γ and γ′ phases and the partitioning behaviour of the alloying elements between the γ and γ′ phases.