Improving the crack resistance of high strength steel manufactured via wire + arc direct energy deposition by controlling the inter-pass temperature

In this study, the influence mechanism of inter-pass temperature on the crack resistance of high strength steel (HSS) component via wire + arc direct energy deposition (WA-DED) was investigated in detail. Three HSS components were manufactured at different inter-pass temperatures (room temperature, 200 °C, and 300 °C). The results revealed that increasing the inter-pass temperature was beneficial for the formation of more martensite and (reverted) austenite. And the morphology of the austenite gradually transformed from blocky to thin-film like as the increasement of inter-pass temperature. Compared to T0 specimen, the fracture toughness, crack initiation energy and crack propagation energy of T200 specimen had been improved 49.2%, 42.3%, and 78.6%, respectively. And the fracture toughness, crack initiation energy and crack propagation energy of T300 specimen had been improved 91.2%, 42.5 %, and 141.9%, respectively. The mechanisms of enhancing crack resistance mainly included the following: more strain-induced martensitic-phase transformation, stronger ability of crack tip passivation, inhibiting crack initiation and propagation. The results proved the feasibility of improving the crack resistance of WA-DED-ed HSS components by controlling the inter-pass temperature.