Microstructure and corrosion resistance of NiCrMoSi-SiC coatings via laser alloyed on Ti6Al4V surfaces

Enhancing the corrosion resistance and strength of Ti6Al4V alloy is essential for extending its service life in high-humidity and salt-laden marine environments. In this study, NiCrMoSi-SiC composite coatings were fabricated on Ti6Al4V surfaces via laser alloying technology using NiCrMoSi/x SiC (x = 0, 2.5, 5, 7.5, and 10 wt%) powders. The results reveal that laser alloying on the Ti6Al4V surface leads to the in-situ formation of a coating microstructure primarily composed of Ti₂Ni and NiTi intermetallic compounds. The addition of SiC enhances the in-situ reactions, generating additional reinforcement phases, such as Al₈SiC₇, Ti₅Si₄, and TiC. The average microhardness of samples S1-S5 is 2.29–2.60 times higher than the hardness of the Ti6Al4V substrate, with sample S4 (7.5 wt% SiC) exhibiting the highest hardness, reaching an average microhardness of 859 HV_0.5. In a 3.5 % NaCl solution, the NiCrMoSi-SiC composite coatings exhibit superior corrosion resistance compared to the Ti6Al4V substrate. The enhanced corrosion resistance of the NiCrMoSi-SiC coatings is achieved through the synergistic effects of corrosion-resistant phases, a refined and dense microstructure, and hydrophobic surface properties. This study demonstrates the multifaceted role of SiC in optimizing the microstructure and enhancing the corrosion resistance of laser-alloyed composite coatings.