Precipitation Hardening of the Additive-Manufactured 17-4 PH Stainless Steel for Medical Applications

This study explores the impact of heat treatment parameters on the hardness and microstructure of 17-4PH stainless steel samples fabricated by additive manufacturing, with a focus on dimensional changes throughout the process. The additive manufacturing method used was Bound Metal Deposition (BMD), which includes digital scanning, 3D metal printing, sintering, and post-processing. It was observed that the printed parts undergo a substantial size increase 16.96% (height) and 18.14% (diameter) to compensate for material loss during the binder removal stage in sintering. Although the sintered parts shrink relative to the printed samples, they remain 3.25% taller and 6.05% wider than the original CAD dimensions. Following sintering, the samples underwent solution treatment and aging at various temperatures and times. Microstructural analysis post-solution treatment revealed a martensitic structure as the predominant phase. Aging caused the formation of strengthening precipitates, leading to peak hardness values of 422.0 and 303.0 HV0.5 at aging temperatures of 480 °C and 620 °C for 1 hour, respectively. Dimensional changes during the precipitation hardening stage were minimal and considered negligible.