Hot isostatic pressing of differently sintered binder jetted 316L stainless steel: Microstructure evolution and mechanical properties

In binder-jetted components, the typical sintered relative density can reach up to 99 %, where remaining pores may degrade mechanical properties, including tensile strength, ductility, and fatigue performance. To enhance manufacturing efficiency in terms of cost and energy, it is crucial to develop post-printing heat treatments to optimize the sintering profile, providing both relative densities of >99 % and dimensional accuracy. This study investigates the effect of hot isostatic pressing (HIP) on the microstructure evolution, pore elimination, and mechanical properties of binder-jetted 316 L SS powder. Sintering at temperatures ranging from 1325 degrees C to 1430 degrees C resulted in relative density between 87 % and 99.5 %, while HIPed specimens revealed that a minimum relative density of 99.5 % could be achieved on any samples sintered at 1370 degrees C or higher temperatures. Microstructure and grain analysis through electron backscattered diffraction (EBSD) showed grain coarsening after HIP treatment, with the highest grain growth occurring in the HIPed specimen sintered at 1400 degrees C (207.4 +/- 5.4 mu m). However, a slight change in grain size was observed in the HIPed specimen sintered at 1430 degrees C due to a noticeable amount of delta-ferrite at the grain boundaries. Mechanical behavior and fractography were compared in sintered and HIPed specimens, and related discussions were leveraged.