Effect of mechanical vibration on microstructure and performance of Fe-based composite coatings fabricated by underwater laser deposition technology

To solve the problem of the uneven composition and poor performance caused by water environment during the underwater laser deposition process, the mechanical vibration assisted underwater laser deposition technology was innovatively proposed, and Fe-based composite layer was successfully prepared. The microstructure, grain type and properties of Fe-based composite layer with and without mechanical vibration were studied and compared. The results showed that the mechanical vibration broke the grain and promoted the formation of more nuclei, which reduced the average grain size by 13.48 %. The solute located in the grain gap was transferred to the liquid molten pool by mechanical vibration, which reduced the Ti content in the intergranular precipitated phase Fe₂Ti and made the Fe₂Ti from coarse continuous distribution to fine discontinuous distribution. Additionally, the mechanisms of mechanical vibration promoting the performance of the composite were analyzed comprehensively. Compared with the composite without mechanical vibration, the composite with mechanical vibration had good corrosion resistance after 30 days of immersion, and the tribo-corrosion resistance was also improved. With the aid of mechanical vibration, the ultimate tensile strength and elongation of the composite were increased by 11.30 % and 22.08 %, respectively, due to the formation of recrystallized grains, high density high-angle grain boundaries, and fine intergranular precipitate. This study was expected to provide a new way to regulate the microstructure and properties of the underwater laser deposition layer, and promote the application of underwater laser deposition technology in marine engineering equipment.