Superior high-temperature mechanical properties and microstructural features of LPBF-printed In625-based metal matrix composites

The growing demands for high-temperature materials, especially in aerospace and energy production, compel thorough explorations of innovative materials. Here, we demonstrate significantly enhanced high-temperature mechanical properties of Inconel 625 (In625) based metal matrix composites (MMCs) fabricated by laser powder bed fusion (LPBF) additive manufacturing. The MMC feedstocks for LPBF were fabricated with fine ceramic particles (i.e., titanium diboride (TiB₂), titanium carbide (TiC), zirconium diboride (ZrB₂) and zirconium carbide (ZrC)) separately mixed with In625 powders. Among the printed specimens, the In625 + TiB₂ showed an exceptional strength-ductility combination at 800 °C as well as an outstanding creep resistance at 800 °C under 150 MPa tensile stress. The detailed microstructural characterization, along with thermodynamic calculation and atomic simulations, reveal that the addition of TiB₂ results in the formation of serrated grain boundaries, (Cr, Mo)-boride phases near the grain boundaries, and nano-dispersed (Ti, Al, Nb)-oxide phases within the matrix. These features effectively suppress the formation of detrimental high-temperature phases and enhance the material’s high-temperature properties. Beyond amplifying the inherent thermal attributes of In625 superalloy, the research highlights the transformative potential of boride doping and the composition design of MMCs specifically for the LPBF process.