Interfacial Microstructural Characteristics and Mechanical Properties of Deposition Layer/Substrate of Marine Steel Component Fabricated by Submerged Arc Additive Manufacturing

Low carbon steel components were fabricated by SAAM（submerged arc additive manufacturing） on EH36marine steel, and the interfacial microstructural characteristics and mechanical properties of the substrate-straight wall were studied systematically. The results show that the microstructure of the straight wall is mainly composed of PF（polygonal ferrite）+ P（pearlite）. EH36 substrate is subjected to the thermal cycling of additive manufacturing process, resulting in the formation of OZ（overheated zone）, RZ（recrystal zone） and IRZ（incomplete recrystal zone）. The straight wall with uniform microhardness distribution is 180 HV1-220 HV1, and higher carbon content of the substrate results in the hardness of HAZ（heat affected zone） slightly higher than that of straight wall. The tensile strength of transverse and longitudinal interface specimens is 474 MPa and 486 MPa, and the elongation is 50% and 39%, respectively, indicating the anisotropy of mechanical properties. The tensile strength of the transverse and longitudinal interface samples can reach 91% and 93%of the substrate. The longitudinal interface specimen fractures at the straight wall in the tensile test, which can confirm the good metallurgical bonding between the substrate and the straight wall. Impact energy of the transverse and longitudinal interface samples is 160 J and 203 J, respectively. The transverse interface sample with slightly lower impact energy is mainly related to the non-uniform microstructure characteristics of the HAZ.