The effects of sintering temperature and hold time on densification, mechanical properties and microstructural characteristics of binder jet 3D printed 17-4 PH stainless steel

Abstract

In this study, the influence of sintering temperature and hold time on densification, mechanical properties, and microstructural characteristics of 17–4 PH stainless steel samples produced by binder jet 3D printing (BJ3DP) was investigated. An ultimate tensile strength (UTS) of 1050 MPa, an elongation at break (A) of >4% and a hardness of ≥330 HV10 through sintering at 1300 °C for 90 min were achieved. The tensile properties are predominantly influenced by porosity as opposed to the grain size or the volume fraction of δ-ferrite. A layered porosity appears in the sintered parts, which is attributed to the layer-wise BJ3DP process. Shrinkage in z-direction is about 2% higher than in x- and y-direction and is therefore anisotropic. Fluctuations in green density of up to 1.2% affect sintered density throughout the study and are compensated best by extended hold times. Microstructural analyses show the expected grain growth and increase in δ-ferrite fraction by increasing sintering temperature and more extensive hold times, while the comparison of fringe and core microstructures reveals little differences of the grain size but significant differences of the fraction of δ-ferrite and porosity.