Investigation of mechanical, oxidation and corrosion performance of Si₃N₄ reinforced TiAl-based composites fabricated via spark plasma sintering technique

This study examines the mechanical behaviour, high-temperature oxidation, and corrosion performance of TiAl-based composites containing varying amounts (0–7 wt%) of silicon nitride (Si₃N₄) fabricated via spark plasma sintering (SPS). Microstructural analysis revealed the in-situ formation of Ti₅Si₃ and Ti₂AlN phases, particularly pronounced at intermediate Si₃N₄ contents, with optimal phase dispersion observed at 1.5 wt% Si₃N₄. 1.5Si₃N₄/TiAl composite displayed a peak compressive strength of 2208 ± 25 MPa and enhanced fracture resistance, attributed to synergistic toughening mechanisms including Orowan strengthening, crack deflection, and particle-stimulated nucleation. Thermogravimetric analysis and surface oxidation morphologies showed that 1.5Si₃N₄/TiAl composite also provides a superior oxidation resistance with the least weight gain of 1.68% compared to 2.77% obtained for the pure TiAl, due to the formation of stable, adherent oxide layers consisting of Al₂O₃, SiO₂, and complex silicates. The developed Si₃N₄/TiAl composites exhibited significant corrosion resistance enhancement in 0.5 M H₂SO₄, with the lowest corrosion current observed in the composite containing 7 wt% Si₃N₄. However, SEM analysis of the corroded surfaces suggests that only the 1.5Si₃N₄/TiAl composite maintains structural reliability over prolonged exposure due to its uniform microstructure and stable passive film formation.