Additive Manufacturing of Crack-Free High Gamma Prime Rene 77 Superalloy: Processing, Heat Treatment and High Temperature Mechanical Properties

Additive manufacturing of Nickel-based superalloys by Selective Laser Melting (SLM) is usually limited to a small range of alloys with low gamma prime forming elements (Aluminium + Titanium < 6wt%) that often suffer from low creep resistance. In this presentation, we are reporting successful fabrication of a modified Rene77 by SLM in crack-free state as well as the development of its post heat treatment process leading to creep performance surpassing the conventional Rene77 and commonly used IN718 up to 650⁰C. The processing methods will be introduced together with the detailed microstructural evolution during the heat treatment, especially the massive grain growth that is rarely seen in SLM superalloys. Tensile and rupture tests were conducted on the optimised microstructure, demonstrating excellent mechanical properties. The deformation mechanism at different temperature and loading conditions will also be presented to highlight the necessity of specialised heat treatment for SLM superalloys. This presentation provides an example case of printing high strength superalloys by SLM via combined considerations in SLM-specific metallurgy, process development, and microstructural manipulation that can lead to sound mechanical properties exceeding the commonly used SLM superalloys.