Enhancing mechanical properties of wire arc additively manufactured SS316L alloy via TLBO-based parameter optimization and microalloying with SiC nanoparticles

The wire arc additive manufacturing has gained widespread adoption in recent years for fabricating large-scale components. However, a coarse columnar grain structure, resulting from directional heat dissipation, leads to reduced mechanical properties. The present study proposed a multi-objective optimization with the addition of an inoculant to enhance the mechanical properties of WAAM. The study aimed to optimize the GMAW-WAAM process variables travel speed (TS), wire feed rate (WFR), and voltage (V) for the bead geometry characteristics bead width (BW), bead height (BH), and bead penetration (BP) on an SS316L substrate. Teacher learning based optimization (TLBO) was used to attain optimal combinations. The two multi-layer structures were then fabricated by considering optimized parameters. The silicon carbide (SiC) nanoparticles were introduced into the molten pool in the fabrication of one wall, and the other wall was fabricated without using SiC. The microstructural evolution was analyzed using optical microscopy and scanning electron microscopy. The SiC-inoculated samples exhibited more refined grains, resulting from heterogeneous nucleation facilitated by the SiC particles within the molten pool. Mechanical characterization, including tensile testing and microhardness, was performed on both SiC-inoculated and non-inoculated samples. The results revealed enhanced YS and UTS in the SiC-inoculated specimens by 25.6 % and 8.25 % respectively, primarily due to the refined grain structure.