Effect Of LPBF Process Parameters on Post-Heat Treatment Microstructures of Hastelloy X

The literature in the laser powder bed fusion (LPBF) domain is very much focused on investigating the effect of process parameters on porosity and as built microstructures, and investigating the effect of heat treatments on densely produced samples. However, there is a lack of systematic studies linking the effect of different process parameters to the heat treatment response of alloys. This study aims to bridge this gap by focusing on the recrystallization behavior of Hastelloy X fabricated by LPBF. Samples with near full density were produced with different laser power, speed, hatch distance, scanning/rescanning strategy. All samples were then uniformly heat treated at 1180 °C for 1h and 2h and air cooled. The Kernel Average Misorientation (KAM) maps of the as-built samples were obtained through Electron Backscattered Diffraction (EBSD) to quantify the stored plastic energy. The post heat treatment microstructures were characterized and presented using scanning electron microscope (SEM). The stored plastic energies, post heat treatment grain morphologies, precipitation (carbide/oxide) types and precipitation densities, and temperature stability were then compared for samples produced with different process parameters. The implications of microstructure engineering through recrystallization in post-process heat treatments of alloys via LPBF process parameter variation were discussed.