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 highhumidity 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 insitu 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 HV0.5. 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.