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Underwater wet flux-cored arc welding (FCAW) process was used to join 2205 duplex stainless steel using Ni-based filler under three different heat inputs of 16.9 kJ/cm, 23.5 kJ/cm and 32 kJ/cm. The arc stability, microstructure and corrosion resistance with different heat inputs were studied. The results showed that the welding process at the heat input of 23.5 kJ/cm was stable with less spatter and good weld appearance. The weld width, weld penetration and dilution ratio increased with increasing heat input. A single-phase austenitic microstructure was obtained for all welds with varied parameters. The heat-affected zone consisted of coarse ferrite and austenite in grain boundary. The grain size of weld zone and heat-affected zone coarsened as the heat input rose. Compared with the base 2205 base metal, the hardness of HAZ increased about 15% while the weld metal changed little. Electrochemical test in 3.5% NaCl solution indicated that the corrosion resistance of the weld metal under high heat input was better, but its corrosion resistance was inferior to that of base materials. Weld metal obtained at 23.5 kJ/cm possessed comprehensive properties in terms of arc stability and corrosion resistance. These results are helpful to promote the application of duplex stainless steel in the fields of nuclear power fields.

The cavitation erosion of weld joint and base metal of China low activation martensitic (CLAM) steel in liquid lead-bismuth eutectic alloy (LBE) at 550 °C was investigated to simulate the cavitation erosion of the first wall and the nuclear main pump impeller in the accelerator driven sub-critical system (ADS). A suit of ultrasonic cavitation facility was self-designed to study the cavitation erosion. By studying the surface micro topography, roughness and mean pit depth of the tested specimens, it was found that some crater clusters and large scale cracks appeared on the tested specimen surface after the formation of numerous single craters, and the base metal exhibited much better cavitation erosion resistance than the weld bead due to the difference in their mechanical properties and microstructures. In addition, by comparing the results of static corrosion and cavitation erosion, it could be concluded that the cavitation erosion and the dissolution and oxidation corrosion in liquid LBE would accelerate mutually.