Hybrid additive manufacturing is the combined utilization of conventional manufacturing (e.g. turning and milling) with additive manufacturing. Additive structures are built by powder bed fusion of metals using laser beam (PBF-LB/M) on top of conventional base bodies. The base bodies can be recurring and simple geometries, as well as worn-out parts for repairment. Thus subtractive machining time, as well as build up height in AM can be saved. Unlike in regular PBF-LB/M, in the hybrid process the bonding to the substrate or base body is highly relevant. Due to the variety of metal alloys in AM, material combinations are possible in hybrid parts. The remelting of the first powder layers to the base body is called bonding zone. The bonding zone needs to be qualified by developing optimal laser process parameters for a strong bonding without crack formation and porosity between the two alloys and the additive built up. Due to the energy input by the layer beam, not only the powder, but also the base body is partially re-melted and heat-effected. This leads to a transition in alloying elements and in material properties like hardness and tensile strength, called transition zone.
To manufacture high quality hybrid parts the following aspects need to be considered and are investigated in advance: The laser process parameters for several material combinations are optimized for the volume built up, as well as for a crack free and dense bonding zone. The first powder layer thickness needs to be quantified. The higher the first layer, the smaller the bonding and transition zone are observed. Cross sections are inspected and characterized by hardness profiles and chemical compositions in the transition zone are quantified. To validate the quality of the bonding zone hybrid tensile tests are conducted without failing in the bonding zone.