Development of heating strategies to reduce crack formation in the manufacturing process of tool components using directed energy deposition

Abstract Due to the increasing number of product variants, the automotive industry is focusing on additive manufacturing processes to enhance the flexibility in the production process. In this context, the directed energy deposition process (DED) offers the potential to manufacture tool components hybrid-additively with the aim to produce vehicle outer skin parts more cost-effectively. The temperature gradient between substrate and additive build-up, which is caused by the heat input of the laser, is a key factor for a crack-free manufacturing process, as it affects the magnitude of residual stresses in the component. In this paper, an improved manufacturing strategy is developed to reduce the temperature gradient and therefore the formation of cracks in the tool component. For this purpose, welding specimens are manufactured additively at different preheating temperatures. Moreover, the influence of a heating plate for in situ heating of the substrate, as well as the influence of stress relief annealing on the manufacturing process is examined to reduce the hardness in the bonding zone of the specimens. In this context, the crack length and hardness in the bonding zone are measured using a metallographic analysis. Based on these results, a tool component is manufactured hybrid-additively without any defects.