Three types of SiAlON ceramic tool materials (α-SiAlON, β-SiAlON, and α/β-SiAlON) were fabricated using hot-press sintering, and the correlations between mechanical properties and cutting performance through the machining of Inconel 718 were systematically investigated. The results showed that the α-SiAlON ceramic tool exhibited the highest hardness, resulting in reduced flank wear. However, its lowest indentation fracture resistance and flexural strength resulted in substantial tool tip wear. The β-SiAlON ceramic tool demonstrated the lowest hardness, resulting in excessive flank wear, while its moderate indentation fracture resistance and flexural strength contributed to moderate tool tip wear. The α/β-SiAlON ceramic tool exhibited moderate hardness, leading to acceptable flank wear, and the highest indentation fracture resistance and flexural strength, resulting in minimal tool tip wear. These results demonstrate that the dual-phase α/β design enables SiAlON ceramic tools to achieve optimal comprehensive performance in superalloy cutting applications.