High Pressure Heat Treatment of Selective Laser Melted (SLM) and Binder Jet (BJ) printed 17-4 PH stainless steel for heat treatment and porosity reduction

The age hardenable 17-4 PH stainless steel has been additively manufactured (AM) using selective laser melting (SLM) and binder jet (BJ) methods. To achieve mechanical properties comparable to wrought steel, the AM steel must be heat treated to reduce porosity and extend fatigue life. Selected test samples were subsequently treated to either a H900 temper or a combined hot isostatic pressing (HIP) and heat treatment process referred to as High Pressure Heat Treatment (HPHT^TM) to achieve the same H900 temper while also reducing porosity. The microstructural analysis of these samples for pore size distribution, phase distribution, grain size and microhardness were conducted. These experimental results indicate that the HPHT process can produce an equivalent microstructure and microhardness to that of conventional H900 heat treatment. In addition, significant reductions in porosity were observed with HPHT. Testing is currently underway to determine the effects HIPing and treatment on the tensile properties and fatigue performance.