Numerical and experimental analysis of thermal-flow-phase transformation in in-situ ceramic reinforced laser cladding Ti coatings

A coupled thermal-flow-phase transformation numerical model was developed and validated through experiments and multi-scale characterization to elucidate the formation and strengthening mechanisms of ceramic phases in laser-clad B 4 C/Ti-6Al-4 V coatings. Within the molten pool, Marangoni convection drives solute transport over a characteristic distance of ∼104.5 mm, significantly surpassing the characteristic solute diffusion length (∼40.6 μm), indicating that macroscopic convection, rather than diffusion, dominates solute redistribution of B, C, and N. Under such intense convection, a nitrogen atmosphere promotes in-situ formation of TiB 2 , TiC, and TiN reinforcements. This multi-phase structure increases the coating hardness to 648 HV 0 . 2 , a 224% enhancement over the substrate. This is primarily attributed to Orowan strengthening and grain refinement, while the wear rate decreases by 92.7%. These results establish quantitative relationships among process parameters, macroscopic morphology, microstructure, and mechanical properties, providing a basis for the digital design and performance optimization of titanium alloy coatings.