Microstructure evolution and mechanical properties of Hastelloy X alloy produced by Selective Laser Melting

Selective laser melting (SLM) is considered as an important additive manufacturing (AM) technology which can fabricate parts with complex geometry. However, it is difficult to predict the optimal SLM-parameters of metallic materials. In this study, orthogonal experiments were designed to study the influence of SLM-process parameters on the density and fabricated quality of Hastelloy X superalloy. Moreover, the relationship between microstructure evolution and performance of deposited microstructure was studied after heat treatment. The laser power, scanning speed and energy density have a significant effect on the density of the fabricated parts. The optimal parameters for determining Hastelloy X are 250 W laser power, 500 mm/s scanning speed, 100 μm hatch space, and 30 μmlayer thickness. The deposited microstructure is a lamellar microstructure in the horizontal direction and a columnar crystal in the longitudinal direction, and the microstructure is mainly martensite. After solid-solution and aging treatment, grain grows up. Martensite decomposes and the carbide M6C was precipitated during the aging process. The strength of the microstructure decreases slightly due to the growth of grain size.