Influence of rhenium and ruthenium on the local mechanical properties of the γ and γ′ phases in nickel-base superalloys

Abstract The effect of rhenium and ruthenium on the hardness of the γ′ precipitates and the γ matrix in nickel-base superalloys was investigated using a nanoindenting atomic force microscope. The partitioning behaviour of the alloying elements and the lattice misfit between the γ and γ′ phase were determined in fully homogenised samples to explain the alloying effects. Rhenium strongly strengthens γ as it predominantly partitions to γ and has a strong solid solution-hardening effect. Ruthenium strengthens both γ and γ′ due to a more homogeneous partitioning behaviour. Ruthenium was found to cause less partitioning of rhenium to γ. This results in a stronger increase of the γ′ hardness. The change in the nanoindentation-derived hardness of both phases could be mainly attributed to the solid solution strengthening of Re and Ru. Keywords: nanoindentationatomic force microscopyrheniumrutheniumsolid solution hardeningpartitioning behaviour Acknowledgements The authors gratefully acknowledge the German Research Foundation (DFG) for funding of this work in the framework of the Research Training Group 1229/1 "Stable and Metastable Multiphase Systems for High Temperature Applications."