Microstructure and properties of underwater in-situ wire-based laser additive manufactured duplex stainless steel

A novel underwater in-situ wire-based laser additive manufacturing (ULAM) technology is proposed for the in-service repair of underwater components in nuclear power plant. Duplex stainless steel (DSS) obtained in air and underwater environments were analysed using material characterisation and testing methods. The effects of underwater additive environments on the microstructure evolution, mechanical properties and corrosion resistance of the specimens were investigated. The results show that the laser heat input is consumed to balance the heat loss of the water-cooled base material during the underwater laser additive manufacturing process, leading to a reduction in the heat input to the molten pool. Underwater specimen exhibit a two-phase balance, with small ferrite grain boundary angles, resulting in better tensile strength and corrosion resistance. Laser reheat treatment leads to a phase change in microstructure, which can enhance the microhardness and the tensile strength. The ULAM system can meet the requirements of actual engineering for cladding layer.