Formation of Dual-Scale TiC Reinforcements Under Different Energy Densities and Their Influence on the Properties of Laser Metal Deposited 316L Composites

Laser melting deposition (LMD) was employed to fabricate 5.0 wt.% TiC-reinforced 316L composite coatings, and the role of laser power in governing microstructure evolution and performance was systematically investigated. Particular emphasis was placed on the laser-power-dependent evolution mechanism of TiC, covering the coexistence of retained undissolved TiC and fine reprecipitated nanoscale TiC phases; critically, this work clarifies their combined regulating effects on hardness, wear, and corrosion behavior, advancing the understanding of structure-property correlation for LMD 316L/TiC composites. The results show that increasing laser power markedly altered melt-pool dynamics, particle dissolution, and interfacial heterogeneity, thereby regulating the process–microstructure–property relationship of the coatings. Owing to the synergistic effects of residual TiC reinforcement, fine-particle dispersion, and microstructural refinement, the P14 and P16 coatings exhibited the highest hardness, reaching ~320–330 HV. However, the best wear resistance was achieved at moderate laser power, indicating that excessive hardening did not necessarily lead to optimal tribological performance because of increased local heterogeneity and particle detachment tendency. Electrochemical results further revealed that corrosion resistance was jointly controlled by passive-film stability and particle/matrix interfacial activation. Among all samples, P12 showed the most favorable overall corrosion performance, reflecting an optimized balance between microstructural uniformity and interfacial stability. These findings demonstrate that appropriate laser power is critical for simultaneously optimizing strengthening and corrosion resistance in the LMD-fabricated 316L/TiC composite.