Laser Composite Welding Of High-Strength Steel: Synergistic Mechanism Of Surface Nanocrystallization On Mechanical And Corrosion Properties

High-strength steels (HSSs) are crucial in the motorized, aerospace, and marine trades, yet their welded joints frequently have low mechanical strength and corrosion resistance. Laser composite welding (LCW) combined with surface nanocrystallization (SN) is a promising approach, although the synergistic mechanism has yet to be fully understood. The purpose of this research is to analyze how SN caused during LCW improves HSS’s mechanical and corrosion properties. In this method, first, HSS plates are prepared and cleaned. Second, LCM, utilizing a fiber laser (FL) and nanostructured filler material (NFM), enables deep-penetration welding and enhanced surface modification in plates. Third, the extremely rapid heating and cooling during LCW caused grain refinement at the surface, which produced nanocrystals smaller than 100nm. Fourth, the microstructure of the welded zone is characterized using techniques like transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to research nanocrystal formation and grain size reduction. Fifth, tensile testing and microhardness measures analyzed mechanical qualities, whereas electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test (PPT) tested corrosion resistance. The findings show that SN causes considerable grain refinement, resulting in grains smaller than 100nm on the weld surface. The refinement significantly improves tensile strength, microhardness, and corrosion resistance by lowering corrosion current density. Finally, the combination of LCW with SN significantly improves the mechanical and corrosion properties of HSS.