Effects of pre- and post-weld heat treatment conditions on microstructures of cast nickel based superalloys GTD-111 in the laser welding process

Abstract

Abstract This research work aims to study the effects of pre-weld and post-weld heat treatment conditions in the laser welding process on the microstructure of cast nickel based superalloy grade, GTD-111. Pre-weld heat treatment conditions consist of a solution treatment at a temperature of 1473 K for 7.2 ks and three over-aging processes at temperatures of 1393, 1413, 1433 K for 7.2 ks. All as-received and pre-weld heat treated specimens received the same post-weld heat treatment, which consisted of a solution treatment at a temperature of 1473 K for 7.2 ks and precipitation aging at a temperature of 1118 K for 86.4 ks. From the results, it can be seen that the higher temperature of the solution treatment with respect to the pre-weld heat treatment provided coarser gamma prime particles precipitating in a gamma matrix with a more uniform microstructure and very fine gamma prime precipitated particles. Furthermore, when followed by the post-weld heat treatment or standard heat treatment of the alloy, the final microstructures of all as-received and pre-weld heat treated specimens were very similar with regard to uniform gamma prime particles. No significant effect of pre-weld heat treatment conditions on the microstructure was found after post-weld heat treatment.