Synergistic effect of B, N and Si multi-element doping on the impact resistance and machining life of diamond-coated tools in zirconia milling

The machining of zirconia ceramics presents significant challenges due to high hardness, intrinsic brittleness, and severe intermittent impact loads generated during milling, which typically induce rapid tool failure. To address this, this study proposes a boron-nitrogen-silicon (B, N and Si) multi-element doping strategy to enhance the comprehensive performance of diamond-coated tools. Theoretically, molecular dynamics (MD) simulations were performed on various doped diamond models to investigate their impact behavior. Results reveal that the B, N and Si synergistic system effectively dissipates impact energy through defect-induced toughening and stress relaxation mechanisms, significantly improving the impact resistance of the diamond lattice. Experimentally, multi-doped diamond-coated tools were fabricated via hot filament chemical vapor deposition (HFCVD). Characterization confirms that multi-element doping optimizes microstructure, alleviates residual stress, and maintains high crystalline quality. Furthermore, systematic zirconia milling experiments demonstrate that the multi-doped tools exhibit superior cutting performance, characterized by low residual stress and excellent toughness. Compared with undoped counterparts, the B, N and Si tools offer a significantly extended service life and produce machined dentures with notably reduced surface roughness. Mechanistic analysis indicates that the synergistic effect enhances coating stability and inhibits catastrophic delamination. This study demonstrates that B, N and Si multi-doping provides an effective solution for the high-efficiency and high-precision machining of zirconia ceramics.