Microstructure and corrosion resistance of TiC/Inconel 625 composite coatings by extreme high speed laser cladding

Extreme high speed laser cladding technology (EHLA) can break the efficiency bottleneck of coating production and provide an effective access to prepare high quality coating. In this study, TiC/Inconel 625 composite coating was produced on AISI 1045 substrates by EHLA and conventional laser cladding (CLA), respectively. The microstructure, elements distribution, XRD pattern and corrosion morphology of the coating under different cladding speeds were characterized. The potentiodynamic polarization and electrochemical impedance spectroscopic were implemented for further investigating the corrosion behaviors of the coating. The results indicated that the microstructure of the both coatings exhibited the same growth pattern, changing from cellular crystals or primary columnar crystals to equiaxed crystals. High cladding speed was accompanied by dendrite refinement and uniform elements distribution. The refiner microstructure benefitting from the high cooling rate contributed to the improvement of the coating corrosion resistance. In the process of EHLA, the incorporation of TiC facilitated the formation of interdendritic carbides playing a role of precipitation strengthening. Many dislocation lines and dislocation tangles formed in EHLA coating are conducive to building a dense passive film on the coating surface. Corrosion tests showed that EHLA coating performed superior corrosion resistance compared to CLA coating.