Directed energy deposition of SS 316L/SiC composites using coincident and coaxial wire-powder feeding

The wire-powder fed directed energy deposition (WP-DED) process enables the fabrication of metal matrix composites (MMCs) with a high deposition efficiency. Lateral wire-powder feeding as well as lateral wire and coaxial powder feeding are two existing methods for WP-DED of MMCs. However, the lateral filler injection limits the fabrication of three-dimensional parts with complex geometry. In this study, we applied the coaxial wire-powder fed DED (CWP-DED) to fabricate the SS 316L/SiC parts with different SiC weight fractions. The effects of SiC content on defects and microstructure of as-built parts were investigated. Three types of interior defects including pores, inclusions, and cracks were observed in as-built samples fabricated with high SiC content. With an increase in SiC content, the grains were refined by dissolved nano-scale SiC particles and more γ-(FeCrNi) phases transformed into α-(FeCrNi) phases. Tensile properties and the underlying strengthening mechanisms of as-built SS 316/SiC specimens were elucidated. This paper will guide the process development for CWP-DED of high-performance MMCs.