The effect of homogenization temperature on the microstructure and high temperature mechanical performance of SLM-fabricated IN718 alloy

Microstructure, mechanical performances at elevated temperature (650 °C) and their correlation of Inconel 718 manufactured by Selective Laser Melting (SLM) were investigated in this paper. Four kinds of heat treatment schemes including homogenization, solution treatment and conventional aging process were carried out to regulate the microstructure in order to obtain the optimum comprehensive mechanical performances at high temperature. The dimension and morphology of grains, subgrains, different precipitates including d phase, strengthening phase, carbides and nitrides were investigated. In addition, their evolution mechanism was also analyzed in detail. Furthermore, for figuring out the effects of microstructures on the mechanical performance, creep rupture test and tensile test were carried out to compare the performance differences of heat-treated samples. The results demonstrated that the heat-treated samples show the better creep rupture performance and higher tensile strength at elevated temperature than that of the wrought. In addition, the sample under homogenization heat treatment in 1080 °C, solution treatment in 980 °C and conventional aging treatment shows the optimum mechanical properties at 650 °C.