Influence mechanism of process parameters on the interfacial characterization of selective laser melting 316L/CuSn10

Abstract Bimetallic structures can combine the performance of dissimilar metal materials to meet the multifunctional requirement in industrial solutions. In this paper, steel-bronze bimetallic structures were fabricated via self-developed multi-material selective laser melting (SLM) equipment. In order to investigate the influence of laser power, scanning speed, and hatching space on the interfacial characterization, three factors and five levels of orthogonal experiments were performed on twenty layers of CuSn10 tin bronze after forming the 316 L stainless steel. Optical microscope (OM), large depth field microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), tensile properties, electron backscattering diffraction (EBSD) and nanoindentation were used to characterize these bimetallic structures to validate the impact from process parameters. The large depth field microscope revealed protrusions at the steel/bronze interface, and its height increased and then decreased with increasing volumetric energy input. Besides, the generation of interfacial defects is related to the interfacial process parameters, and it is found that the types of defects are mainly classified as holes and cracks. Insufficient energy will cause cracks in the horizontal direction and then lead to bonding failure. Conversely, higher energy input will generate microcracks in the vertical direction. The defects near the interfacial region are the main factors affecting the ultimate strength of the bonding strength. As a result, the steel-bronze bimetallic structure displays optimal joint ultimate strength of 459.54 ± 3.08 MPa with elongation of 5.23 ± 0.65%, and minimum joint ultimate strength of 199.02 ± 0.56 MPa with elongation of 1.70 ± 0.22%. Their fracture morphology also exhibited gully-like and fan-shaped features, respectively. Additionally, the EBSD results show that there are fine grain regions appeared in the interfacial region, which helps increase the average nano-hardness of the interfacial region. This study provides a reference for the influence of process parameters on the interfacial characterization and mechanical properties of steel-bronze bimetallic parts prepared by selective laser melting.