Microstructure and Corrosion Resistance of Low-Carbon Martensitic Stainless Steel 0Cr13Ni4Mo with 3%Cu Addition

Low-carbon martensitic stainless steel 0Cr13Ni4Mo is widely used in hydraulic turbine runners, oil and gas storage, high-pressure pipes in power generation, and other fields owing to its high strength, good corrosion resistance, and good welding properties. However, to enhance its performance under different environments, there is a need to improve its strength and corrosion resistance. Previous studies have found that adding Cu to 0Cr13Ni4Mo steel enhances its strength through the formation of Cu-rich precipitation. However, the impact of Cu on the corrosion behavior of the 0Cr13Ni4Mo steel is not yet well understood. This study aims to investigate the effect of adding 3%Cu (mass fraction) on the microstructure and corrosion resistance of low-carbon martensitic stainless steel 0Cr13Ni4Mo using various techniques such as SEM, XRD, TEM, APT, and electrochemical testing. The results show that after solution treatment at 1050(o)C, Cu is uniformly distributed on the lath martensite matrix. After tempering at 400(o)C, Cu forms minute nanoclusters with a large number of Fe atoms segregated. On the other hand, tempering at 500(o)C leads to the growth of Cu-rich precipitates with a size of 5-10 nm, where Cu atoms are mainly segregated at the core of the precipitates and are in a coherent relationship with the martensitic matrix. Carbides grow from Fe-rich nanoclusters to Cr-rich precipitates during the tempering process. The addition of 3%Cu to low-carbon martensitic stainless steel shows excellent corrosion resistance after tempering at 500(o)C. This may be due to the emission of Cr atoms to the surrounding matrix during the growth of Cu-rich precipitates, which reduces the Cr-depleted zone caused by Cr-rich carbides in the matrix, thus reducing the corrosion sensitivity of 0Cr13Ni4Mo martensitic stainless steel with 3%Cu addition. These findings provide a better understanding of the role of Cu-rich precipitates on the corrosion performance of low-carbon martensitic stainless steels and provide guidance for the design of corrosion resistant steels.