Characterization of microstructure and texture of lean duplex stainless steel 2101 produced by underwater laser wire direct energy deposition

Lean duplex stainless steel 2101 (LDX 2101) is a promising material to replace 304 austenitic stainless steel in nuclear power plant in the future and it has been widely studied for its good economy, mechanical properties and corrosion resistance. Aiming at the underwater maintenance of nuclear power, the microstructure and texture evolution of laser wire direct energy deposition in underwater environment were studied by means of optical microscope and electron backscatter diffraction. The results show that the rapid cooling effect of underwater environment on the molten pool inhibits the transformation from ferrite to austenite. Since ferrites have the lowest surface energy, most of them were precipitated along the dense-packed (111) α and (110) α planes. The deposition structure shows typical cube texture and Goss texture. Although the texture of austenite is not as strong as that of ferrite passing through the deposition layer, the results show that the austenite phase was formed with a close Kurdjumov-Sachsorientation orientation relationship with respect to the ferrite phase. It is also found that the cyclic reheating effect of laser wire direct energy deposition not only changes the microstructure and texture, but also affects the grain size and the proportion of special grain boundaries. Improving the content and distribution uniformity of Σ3 grain boundary in the deposition structure is beneficial to improve the corrosion resistance.