Microstructure and properties of non-contact ultrasonic-assisted underwater adjustable-ring-mode (ARM) laser cladding coating of 2205 duplex stainless steel

The in-situ repair of 2205 duplex stainless steel was conducted in air and underwater using non-contact ultrasonic assisted ARM laser wire-feeding cladding technology, and the interaction mechanisms of ultrasound and water on the formation, microstructure, mechanical properties and corrosion resistance of the laser cladding layer were investigated. The surface of the coating in air was smoother and more uniform compared to the underwater coating. Additionally, the fast cooling rate during the underwater cladding process inhibited the phase transformation of the α → γ, increasing the proportion of the α phase and the amount of Cr₂N precipitation, which led to reduced corrosion resistance. Meanwhile, the smaller grains and fewer LAGBs in the underwater cladding layer resulted in higher microhardness. After applying ultrasound, the surface flatness of the coatings improved, and the cavitation effect of ultrasound effectively refined the grains, reduced the porosity and decreased the texture density. Furthermore, ultrasound reduced the temperature gradient and solidification cooling rate during the cladding process, increased the proportion of α phase, and decreased the Cr₂N precipitation. Ultimately, the mechanical properties and corrosion resistance of the cladding layer were enhanced.