Microstructure and Properties of Fusion Electrode Gas Shielded Weld Surfacing Layer on FV520B Steel Surface Before and After Laser Quenching
Single-layer single-pass,two-layer multiple-pass,and three-layer multiple-pass homogeneous overlay tests were conducted on FV520B steel plate by melting electrode gas shielded welding.The laser quenching treatment was applied to the single-layer single-pass surfacing layer.The microstructure,hardness,and corrosion resistance of different surfacing layers and laser quenched surfacing layers were studied.The results show that the surfacing layer consisted of lath martensite,a small amount of δ ferrite and some carbides,and the microhardness was 350 HV,which was 14.7％higher than that of the base metal.The 8 ferrite in the microstructure of interface of interlayer and interpass decreased.The highest hardnesses at the interlayer and interpass interfaces reached 380.3,373.5 HV,which were about 8.0％and 6.7％higher than that of the surfacing layer,respectively.The corrosion rate of the surfacing layer was lower than that of the base metal,and as the number of surfacing layers increased,the corrosion rate remained unchanged.After laser quenching,the martensite of the surfacing layer became finer,and the thicknesses of the quenching zone and the heat affected zone were 194.3,186.3 μm,respectively.The highest hardness of the surfacing layer after laser quenching increased to 390.4 HV,and as the distance from the quenched surface increased,the hardness first increased and then decreased.The corrosion rate of the surfacing layer after laser quenching was lower than that without laser quenching.
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