Interface microstructure and nano-mechanical properties of Fe-SiC composites fabricated by laser-directed energy deposition

This study investigated the interfacial microstructure and nano-mechanical properties of iron-silicon carbide (Fe-SiC) parts with 5, 10, and 30 vol% SiC fabricated using the laser-directed energy deposition (LDED) process. A scanning electron microscope (SEM) and a transmission electron microscope (TEM) were employed to characterize the interfacial interactions between SiC particles and pure Fe. Dissociation of SiC particles was observed in all compositions, which resulted in the precipitation of pure carbon in the Fe-C-Si solid solution. Both SEM and TEM line scans revealed compositional diffusion at the interface between the reinforcements and the matrix. Nano-indentation tests were conducted for all compositions to characterize the local mechanical responses. The nano-indentation hardness and elastic modulus were minimal in the carbon-rich regions, varying with SiC fractions in the sequence as Fe-5SiC > Fe-10SiC > Fe-30SiC. In contrast, the maximum hardness in the matrix followed the opposite trend, with the highest values observed for Fe-30SiC and the lowest for Fe-5SiC. Similarly, the maximum elastic modulus in the matrix followed the same variation sequence as the minimum elastic modulus values. These findings highlight the low thermodynamic stability of SiC in ferrous materials during the LDED process. Adjusting the SiC concentration offers a pathway to customize the microstructure and properties of Fe-SiC composites. • Fe-SiC with varying SiC fractions were built by laser-directed energy deposition. • A diffused interface was observed between Fe metal and SiC ceramic. • Formation of pure carbon and Fe-C-Si solid solution was due to SiC dissociation. • Nano-mechanical response was evaluated, covering reinforcements and matrix. • Nano-indentation showed minimal hardness and elastic modulus in carbon-rich areas.