Zinc-induced embrittlement in nickel-base superalloys by simulation and experiment

The high cost of Re has driven interest in processes for recovering Re from scrap superalloy parts. In this work thermodynamic modelling is used to study Zn-induced embrittlement of a superalloy and to direct experiments. Treating superalloy powder with Zn vapour reduces the average particle size after milling from approximately 130 mu m to 0.5-10 mu m, vs. 100 mu m for untreated powder. Simulations predict the required treatment time to increase with temperature. Agreement between predictions and experiments suggests that an embrittling liquid forms in less than an hour of Zn vapour treatment between 950-1000 degrees C and partial pressures of Zn between 14-34 kPa (2-5 psi).