Effect of Heat Treatment on Microstructure and Residual Stress of GH3536 Superalloy Fabricated by Selective Laser Melting

Widely applied in the aeronautic and aerospace industries, Ni-based superalloy GH3536 has outstanding strength and oxidation resistance at elevated temperatures. In this study, GH3536 specimens are fabricated by selective laser melting (SLM) followed by heat treatment (HT). The microstructure, residual stress, tensile strength, and hardness of both the SLMed and SLM-HTed specimens are investigated. Experimental results demonstrate that the SLMed specimens possess a supersaturated solid solution state due to the rapid cooling, and residual tensile stress exists in the subsurface periodically along the building direction. After heat treatment, Mo-rich carbides precipitate from the matrix, reducing the degree of solid solution. In addition, residual tensile stress caused by SLM converts to compressive stress due to heat treatment, and the periodic distribution of subsurface residual stress disappears. The study concludes that the heat treatment retards the solid solution strengthening and grain boundary strengthening of the SLMed specimens, resulting in a decrease in hardness and yield strength and a 53% increase in fracture elongation. This study can provide guidance to the application of SLMed GH3536 Ni-based superalloys.