Research on corrosion propagation mechanism in laser-arc hybrid high-nitrogen steel welded joint by dendritic connectivity

Localized corrosion in laser–arc hybrid welded high-nitrogen steel joints is strongly affected by microstructural heterogeneity. This study focused on the effect of welding speed on dendritic connectivity and the correlation with localized corrosion behavior. With the change of laser–arc hybrid welding speed, the relationship between precipitated phase connectivity and corrosion morphology was analyzed. The resulting microstructures and corrosion morphologies were characterized using SEM, TEM, and electrochemical testing. The skeletonization approach was applied to quantify corrosion path connectivity through branch and junction analysis. The experimental results showed that the Cr depletion zones were responsible for initial pitting corrosion. The XPS etching experiment showed that the repassivation film provided protection for weld seam surface. The corrosion current density decreased to 4.98 μA cm−2 as welding speed increased from 0.6 to 0.8 m/min. This study confirmed that higher welding speeds suppress dendritic interconnectivity, limiting long-range corrosion propagation and promoting more localized corrosion behavior.