Design of Solutionizing Heat Treatments for an Experimental Single Crystal Superalloys

Abstract

The heat treatment response between 1170C and 1320C of an experimental single crystal Ni base superalloy is presented. The temperature range for solutionizing the alloy is determined by combinations of holding time and temperature. The effects of long isothermal holding within and beyond this solutioning temperature range are studied. Heat treatment steps below the -solvus temperature stabilize the eutectic phase, while steps above the solvus temperature improve the homogenization and reduce eutectic phase fraction. However, prolonged holding above the solvus temperature indicates up-hill diffusion at the eutectic region leading to incipient melting. A new solutioning heat treatment approach with continuous heating between solvus and solidus is proposed