The Effect of Metallic and Oxide Additives on Spark Plasma Sintering and Properties of Silicon Carbide Components

This study investigates the influence of metallic (Al, Ti + H۳BO۳) and oxide (Al۲O۳–Y۲O۳ and Al۲O۳–Y۲O۳–MgO–CaO) sintering aids on the densification behavior and mechanical properties of silicon carbide (SiC) consolidated by spark plasma sintering (SPS). The primary objective was to reduce the inherently high sintering temperature of SiC while maintaining or improving its mechanical performance. Experimental results demonstrate that appropriate additives significantly lower the sintering onset (as low as ۱۲۷۴ °C for SiC ۵Al) and enable high final densities (relative densities >۹۸%, e.g., ۹۸.۴% for SiC ۳Al۲O۳ ۲Y۲O۳) at overall sintering temperatures below ۲۰۰۰ °C. Among the formulations tested, SiC ۱۰Al achieved a flexural strength of ۴۱۷ MPa (۹۷.۲% relative density), whereas SiC ۳Al۲O۳ ۲Y۲O۳ exhibited a Vickers hardness of ۲۹.۶ GPa (۹۸.۴% relative density). Microstructural observations and phase analysis suggest that liquid-phase formation and additive–matrix interactions govern the observed densification and mechanical trends. These findings indicate that SPS combined with selected metallic or alumina–yttria-based additives represents an effective and industrially scalable route for fabricating dense, high-performance SiC components suitable for demanding applications in the energy, electronics, and automotive industries, as well as in wear-resistant tooling.