Effect of interface orientation in laser powder bed fusion of IN718/GRCop-42 bimetallic parts for Aerospace

Additive manufacturing of bimetallic parts has gathered significant interest in recent years. Of particular relevance is the combination of Ni-based superalloys and Cu-based alloys suitable for high temperature applications, such as those found in aerospace rocket engines. To provide confidence in the production of such bimetallic parts, a detailed understanding of the process-structure relationship is required. This study investigates the effect of deposition sequence and recoating direction on the interfacial microstructure evolution in samples where material is graded through horizontal, vertical and angled interfaces. The samples in this study are produced through laser powder bed fusion of IN718 and GRCop-42, using a Schaeffler Aerosint selective powder deposition recoater. Analysis was conducted through a combination of backscatter electron imaging, x-ray diffraction, energy dispersive spectroscopy, and electron backscatter diffraction. For a horizontal interface, the deposition sequence has a significant effect on the presence of defects and phase formation at the interface. The recoating direction is shown to have an influence on the mixing behaviour for vertical and angled interfaces, with a gradual transition of the alloys produced when the interface is aligned parallel to the recoating direction. In contrast either a significant crossing of the first-deposited material across the interface occurs, or a sudden change in composition develops when deposition is perpendicular to the interface. On the basis of these findings, design rules can be developed to ensure the fabrication of suitably designed bimetallic parts for high temperature applications such as rocket engines in the aerospace sector.