Laser additive manufacturing enables the one-step fabrication of complex parts. This technology has been applied for the tooling with the advantages such as fast tool development, low material cost and high geometry freedom. However, pores and carbides network, which are not avoidable from the LPBF process, deteriorate the fatigue strength significantly. Hot isostatic pressing (HIP) with quenching is a powerful post treatment, which not only densifies the material but also modifies the microstructure.
In this study, AISI M3:2 samples were produced by LPBF and then were either austenitized and quenched in a HIP unit and subsequently vacuum tempered or were only hardened and tempered in a vacuum oven. The corresponding microstructure was analyzed by optical microscopy, scanning electron microscopy (SEM) employing energy-dispersive X-ray spectroscopy and X-ray diﬀraction (XRD). The fatigue strength was determined by rotation bending tests. Fracture surfaces were observed under SEM for failure analysis. While both post treatments lead to similar microstructure, the fatigue strength is significantly improved by the HIP process.