Enhancing the surface wear resistance of Ti6Al4V alloy via laser-driven grinding with in-situ BN/graphite alloying

To address the high energy consumption and elevated cost bottlenecks arising from the conventional separation of surface modification and finishing processes for titanium alloys, this study proposes an innovative laser-driven grinding method. Utilizing its intense thermo-mechanical coupling effect in combination with a separable BN/Graphite composite coating, a multi-component reinforcement layer rich in non-stoichiometric Ti(C x N 1−x ) continuous solid solution and orthogonal TiB phases was successfully fabricated in situ on the Ti6Al4V surface, concurrently inducing significant refinement of the matrix phase. The results demonstrate that the optimized coating ratio effectively suppresses the directional growth tendency of coarse columnar dendrites via a potent Zener pinning effect, establishing an isotropic ultra-fine grain network. Consequently, the modified layer achieves a remarkable surface hardness of 901.95 HV 0.2 and an enhanced theoretical yield strength of 1847.6 MPa. SEM and XPS characterizations confirm the formation of a protective tribo-chemical oxide film on the laser-ground layer, significantly enhancing wear resistance under dual counterface conditions. Under the extreme Hertzian contact stress imposed by rigid Si3N4 ceramic balls, the loose wear debris undergoes continuous mechanical compaction and solid-phase sintering, dynamically constructing a dense, self-lubricating tribo-layer. This study provides crucial technical support and a practical reference for the high-performance manufacturing of Ti6Al4V components with extended service durability.