Microstructure and Mechanical Properties of Hybrid-Manufactured Maraging Steel Component Using 4% Nitrogen Shielding Gas Fabricated by Wrought-Wire Arc Additive Manufacturing

Abstract

Recent advances in hybrid-manufactured steel components have provided more geo-metrical freedom for the manufacturing of parts with desired properties. The wrought-wire arc additive manufacturing (WAAM) components using different shielding gases were fabricated in this paper. The results showed that there were four parts in the microstructure, including the WAAM deposition zone, grain growth zone, heat affect zone (HAZ) and substrate zone. The grain growth zone containing large martensite laths had a significant effect on the final tensile strength. In the WAAM deposition zone, the austenite content increased from 2.5% to 7.6% because of the addition of 4% nitrogen. The fracture position shifted from the grain growth zone of the N2-0% sample to the WAAM deposition zone of the N2-4% sample owing to the strengthening machines of solid solution and finer grain. Nano-precipitate Cr2N plays an important role in grain refinement, which is believed to enhance the mechanical properties of the grain growth zone. Under a 4% nitrogen content in the shielding gas, the tensile strength of the hybrid-manufactured sample using 4% nitrogen shielding gas was 1186 MPa, which is approaching the level of the WAAM-fabricated sample.