Abstract: In order to effectively repair the surface damage of FV520B steel and improve the corrosion resistance of the repaired surface, the method of surfacing followed by laser surface treatment was applied, i.e., surfacing was first performed by open-arc swing cladding method with martensitic-type flux-cored wires on the base material of the FV520B steel, and laser surface treatment was performed on the surfaced layer with two types of lasers (semiconductor and fibre optic lasers), respectively. The microstructure and hardness of the surfaced layer, the elemental distribution between the surfaced layer and the base material, as well as the microstructure, hardness, corrosion and depth of laser effects of the surfaced layer after laser surface treatment were investigated. The results show that the surfaced layer consists of martensite, δ-ferrite, retained austenite and carbide, and the hardness is about 480 HV0.3, which is about 33.33% higher than the base material, and the metallurgical bonding between the surfaced layer and the base material is well established. After laser surface treatment, the surfaced layer is categorised into the original surfaced zone, the heat affected zone and the remelted zone. In the heat affected zone, the hardness decreases, which is related to the tempering effect of the laser surface treatment, in the remelted zone, the hardness is comparable to the original surfaced zone. The results of the immersion experiments show that the laser surface treatment improves the corrosion resistance of the surfaced layer. As the scanning speed decreases, the depth of laser action increases, but the hardness does not change much. Compared with the fibre laser, the semiconductor laser has a greater depth of effect, but the surface hardness after both laser treatments is basically the same.

Key words: FV520B steel, surfaced, laser surface treatment, microstructure, hardness