Effect of hot isostatic pressing on the microstructure and mechanical properties of 17-4PH stainless steel parts fabricated by selective laser melting

17-4PH stainless steel parts, fabricated by selective laser melting, were subjected to the solution and aging treatments conducted under vacuum and hot isostatic pressing (HIP) conditions. The microstructure of as-built and heat-treated specimens were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Mechanical properties were evaluated using microhardness and tensile testing. The relative density of the as-built samples was improved after the conduction of HIP treatment. Microstructural characterization showed that precipitates with the co-occurrences of Cu-, Mn-, Si- and Nbenrichments were formed in the HIP-processed specimen. Results of mechanical testing indicated that a simultaneous improvement of tensile strength and ductility could be obtained through solutionizing and aging treatments done in the HIP followed by a high-pressure gas quenching. In addition, a significant enhancement of tensile strength without sacrificing ductility could be attained by combining solutionizing treatment done under high pressure and consequent aging followed with water cooling.

Automated summary

Selective laser melting fabricated 17-4PH stainless steel parts were subjected to solution and aging treatments conducted under vacuum and hot isostatic pressing (HIP) conditions. The microstructure of the samples were characterized, showing an improvement in relative density after HIP treatment. Mechanical testing results indicated that a simultaneous improvement of tensile strength and ductility could be obtained through solutionizing and aging treatments done in HIP, with a significant enhancement of tensile strength achieved by combining high pressure solutionizing and water cooling aging treatments.