Microstructural evolution and property optimization of TiC/FeNiCoCr composite coatings induced by laser remelting

Abstract

The study conducts a comprehensive comparison of the phase constituents, microstructural features, nanoindentation characteristics, corrosion properties, and cavitation erosion resistance of TiC-reinforced FeNiCoCr composite coatings produced via laser cladding (LC), both prior to and following laser remelting (LRM). The underlying mechanisms of microstructural modification and comprehensive performance enhancement induced by remelting treatment are thoroughly elucidated. The findings indicate that while the dominant phase composition of the coating (FCC + TiC) remained unchanged after remelting, notable alterations occurred in the morphologies and spatial arrangement of TiC particles. Compared to the LC coating, the TiC particles in the LRM coating were considerably refined and more uniformly distributed, thereby minimizing their agglomeration and promoting stronger interfacial adhesion between the reinforcement and the matrix. Due to the reduced cooling rate during remelting, the grains exhibited stronger preferential orientation along with pronounced dynamic recrystallization, resulting in significant grain refinement. Concurrently, the proportion of high-angle grain boundaries (HAGBs) increased in the LRM coating, while the remelting process also mitigated stress concentration and enhanced coating stability. The refined morphologies and more uniform dispersion of TiC particles notably enhanced the nanohardness of the LRM coating, while maintaining its ability to bear loads and resist plastic deformation. Electrochemical tests revealed that both LC and LRM coatings exhibited corrosion resistance comparable to 316 stainless steel (SS), while the LRM coating demonstrated further improved anti-corrosion performance owing to its denser microstructure and optimized distribution of reinforcing phases. Furthermore, the combined improvement in mechanical strength and corrosion resistance imparted the LRM coating with outstanding resistance to cavitation erosion. Linear fitting analysis demonstrated that the cavitation erosion resistance (Re) exhibited strong correlations with both nanohardness (H) and corrosion current density (I_corr) (R² > 0.9). Remarkably, the LRM coating maintained structural integrity after cavitation erosion testing, demonstrating exceptional service stability.