On the effect of Ru upon creep behaviour and dislocation evolution in Ni-based single crystal superalloys

Ni-based single crystal superalloys are important structural materials especially for high temperature applications. As one of the key elements added in Ni-based single crystal superalloys, Ru can significantly alter the creep performance of Ni-based single crystal superalloys at high temperatures. The exact role of Ru upon creep behaviour is still under debate, and current research of Ru effect has mainly focused on the change of misfit, inverse partitioning of elements and suppression of topological-close packed phases. Since creep properties are closely associated with dislocation behaviour, in the present work, special focus is placed on the effect of Ru upon the dislocation evolution at high temperature and low stress creep regime. By employing both interrupted and fractured creep tests and corresponding scanning transmission electron microscopy analysis, microstructural and dislocation evolution were systematically investigated after creep test. An addition of 2 wt% of Ru significantly enhances the creep life, and this Ru effect is mainly attributed to the formation of mature dislocation network along with suppression of topological close-packed phases. This work provides further insight into superalloy design for choosing the potential solute elements, aiming for improved creep properties. Data Availability: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.