Research progress on impact toughness of supermartensitic stainless steel

Supermartensitic stainless steel has been widely used in many industrial fields for its excellent comprehensive properties. However, with the development of some modern engineering structures in the direction of large-scale, service conditions are more severe for supermartensitic stainless steel, which increases requirements for impact toughness of its components. In this paper, research progress of impact toughness of supermartensitic stainless steel was focused on, aiming to provide reference for optimization of toughness of base metal and welded structures. Firstly, effects of microalloying elements such as N, Nb, Ti, Cu and V on toughness of base metal was introduced. Addition of N, Nb, Ti, V could form precipitates such as nitrides and carbides in microstructure, which damaged impact properties of the material. Addition of appropriate Cu element did not form precipitates that was harmful to toughness, but toughness of the material was improved because it promoted formation of toughening phase reversed austenite. Secondly, toughness level of supermartensitic stainless steel weld under different welding processes was summarized from two perspectives of welding method and shielding gas. Impact toughness of welded joints of turbine runner with the existing MAG welding process was lower than that of base metal, which restricted further development of hydropower industry. Finally, it was pointed out that in-depth study of microalloying technology and optimization of welding process and heat treatment process were important directions to promote application of supermartensitic stainless steel.