Hybrid parts produced by deposition of 18Ni300 maraging steel via selective laser melting on forged and heat treated advanced high strength steel

Abstract Long production times, the associated high costs of the products and product size limitations belong among current issues of selective laser melting (SLM) technology. Hybrid products containing small and complex-shaped parts deposited by SLM on the forged, rolled or hot stamped semi-products could offer a practical solution to these limitations. Cylindrical hybrid parts were additively manufactured by depositing 18Ni300 maraging steel on the cylindrical semi-products of CMnAlNb low-alloy advanced high strength steel (AHSS). The AHSS was used either in forged and air cooled condition or after heat treatments typically used for inducing the TRIP (transformation induced plasticity) effect. Various post-build heat treatments of the hybrid parts were performed. The mechanical properties of the hybrid parts were determined by hardness measurement across the interface and by a tensile test of the dissimilar joints. All tensile samples fractured in the high-strength steel side, several millimetres from the interface. Microstructure analysis of both materials and the interface region was carried out using light and scanning electron microscopes. The hybrid parts had the ultimate tensile strengths of 840-940 MPa, with total elongations of 12-19%. The best combination of tensile strength and elongation was obtained with two-step heat treatment of the TRIP steel prior to additive manufacturing with no post-build heat treatment of the hybrid part.