Additive manufacturing of parts with a mass superior to a ton implies the use of highly productive processes for it to be industrially feasible. The latter may induce a high heat-input and therefore low cooling rates in the deposited material. In the case of low alloy steels, where the cooling rate is critical to achieve good mechanical properties, the increase in deposition rate may cause the mechanical properties in the finished part to drop and make them unusable for critical applications. This study aims at understanding the impact of the very high deposition rate (15 to 46 kg/h) on the mechanical properties of deposited low alloy steel. To do so, three parts manufactured using different deposition rate, but also different heat-input have been characterized using impact energy testing. Preliminary work has shown very promising toughness at low temperature for the as-built parts regardless of the deposition rate. Hence, Ductile to Brittle Transition Temperature (DBTT) testing has been performed in order to estimate the latter for each manufactured part. The presented work will link the mechanical results obtained together with the microstructural state and thermal history of each deposit.

Keywords: WAAM; low alloy steel; acicular ferrite; toughness; high deposition rate