Heat treatment improved the corrosion resistance of laser- welded joints of SK5 steel with the notch effect

A high energy density heat source was a candidate choice for the laser welding of dissimilar steels. A thin heat-affected zone (HAZ) demonstrated the high precision of the laser welding treatment, and the performance was superior to that of traditional arc welding. This investigation examined the tensile deformation behaviour of SK5 steel under constant laser welding parameters, and the electrochemical properties of the joint were also characterized in brine water (3.5% wt NaCl solution). A martensitic structure existed in the fusion zone, and it deteriorated the mechanical performance of the substrate with the welding treatment. Annealing at a temperature of 450 °C for 1 hour was used to promote the performance of the SK5 steel. Meanwhile, the annealing treatment decreased the thermal stresses to inhibit crack initiation from the grain boundary due to diffusion of the carbon atoms in the heat-affected zone. Additionally, the corrosion current densities of the laser-welded specimens with and without the annealing treatment were 2.97×10 -5 A/cm 2 and 5.97×10 -6 A/cm 2 , respectively. The annealing treatment effectively enhanced the tensile and corrosion resistance of the SK5 steel in brine water. It was demonstrated that dendrite coarsening in the fusion zone effectively enhanced the corrosion resistance of SK5 steel.