Taguchi design for heat treatment of Rene 65 components

Rene 65 is a nickel-based superalloy used in aerospace components such as turbine blades and disks. The microstructure in the as received condition of the superalloy consists of ~40% volume fraction of gamma prime precipitates, which give such high strength that causes issues during thermomechanical processing. The goal of this study was to develop a heat treatment for manufacturing of Rene 65 components by changing the size distribution and volume fraction of those precipitates. Gamma prime in this alloy is observed in three sizes, ranging from a few μm to tens of nm. For the design of the heat treatments, Design of Experiments (DOE) has been used, and more specifically Taguchi’s L8 matrix. The four factors that are examined are cooling rate, hold temperature, hold time and cooling method to room temperature. The levels of the factors were two (high and low) with replication. Microstructures were characterized by Scanning Electron Microscopy and mechanical properties by Vickers microhardness testing.