Microstructure and material properties of 3D-printed bimetallic steels

Corroded steel components can be repaired by laser 3D printing technology. However, studies on the mechanical behaviour of repaired areas composed of a substrate and deposited material are still limited. In this study, 316 L stainless steel powder was deposited on Q355B steel plates through 3D laser printing technology to form bimetallic steel plates. Uniaxial tensile tests were conducted on Q355B steel coupons, laser 3D-printed 316 L stainless steel coupons, and bimetallic steel coupons. The test results revealed that ductile fracture occurred in the bimetallic steel coupons. The mechanical properties of bimetallic steel are considerably correlated with the properties of the cladding layer and substrate. During the loading process, the axial strain of the bimetallic steel coupons was uniformly distributed along the thickness direction, indicating that the substrate and cladding materials maintained excellent cooperative deformation. Bending tests and scanning electron microscopy observations indicate that a reliable and robust metallurgical bond is established at the interface between the substrate and the cladding layer. The interface area can be divided into the cladding layer, the carburising zone, the decarburised zone, and the Q355B substrate. The microhardness results indicate a considerable increase in the hardness of the carburised layer, which enhances the tensile strength of the bimetallic steel. On the basis of the experimental results, a three-stage model for predicting the stress‒strain curve of bimetallic steel was established.