Laser Remelting-Induced TiC Redistribution Regimes in DED TiC/Inconel 625 Metal Matrix Composite Hardfacing

Laser directed energy deposition (DED) additive manufacturing of TiC-reinforced Inconel 625 metal matrix composite (MMC) coatings is a promising route for hardfacing and repair of structural steel components, but it produces spatially heterogeneous TiC particle distributions that compromise microstructure uniformity and mechanical performance. In this work, post-deposition laser remelting was applied to as-deposited TiC/Inconel 625 composite coatings across a range of effective energy densities ( E eff = 22.2–133.3 J/mm 2 ), and its influence on TiC particle behavior, microstructure evolution, and hardness was systematically investigated. In-situ infrared thermal monitoring, cross-sectional image analysis with Voronoi tessellation, and dimensionless time-scale analysis were combined to characterize three distinct behavioral regimes: Marangoni-driven redistribution with improved particle spatial homogeneity at low E eff (Regime I); TiC dissolution and complex carbide reprecipitation yielding maximum matrix microhardness at intermediate E eff (Regime II), though accompanied by vertical solidification cracking in the remelted zone; and buoyancy-driven particle flotation with near-baseline hardness at high E eff (Regime III). Regime boundaries are described by the normalized time-scale ratios t life / t d and t life / t float . Regime I defines a robust process window that simultaneously improves surface roughness, particle spatial homogeneity, and near-surface matrix hardness without cracking, whereas Regime II offers the highest matrix hardness but carries a cracking risk requiring additional stress mitigation. The dimensionless timescale framework can be extended to other laser-processed composite systems by substituting system-specific parameters.