In this research, the effect of adding 2.5, 5.0 and 10 wt% niobium (Nb) as a binding agent was investigated for High Pressure-High Temperature (HPHT) sintering of polycrystalline diamond (PCD). Samples were sintered at 1750 °C and 7.7 GPa. Detailed characterization of the as-sintered materials revealed a uniform dispersion of the Nb additives in the diamond matrix and no interfacial cracking was observed. Higher concentration of binder increased tendency to intergranular failure. The formation of NbC and NbC0.84 phases after sintering was identified, indicating that some of the matrix carbon may have undergone graphitization2026-10