ScholarWorks@성균관대학교

초록

Thermomechanical treatment is widely employed to enhance the mechanical performance of medium-carbon steels; however, it often compromises their corrosion resistance and shortens service life, particularly in corrosive environments. The present study aims to simultaneously improve the mechanical and electrochemical properties of 45CrNi high-strength steel through optimized thermomechanical treatment. The as-received steel exhibited a pearlitic microstructure within a ferritic matrix, with an average grain size of 151 & micro;m. After thermomechanical treatment with tempering at 470 degrees C, the steel developed a refined microstructure with an average grain size of 9.4 & micro;m, comprising 71 vol.% tempered martensite and 29 vol.% retained austenite. This phase transformation significantly improved the mechanical properties: tensile strength increased by 43%, micro-Vickers hardness by 64%, and impact toughness nearly doubled. In parallel, electrochemical performance was markedly enhanced, as evidenced by a reduced corrosion current density of 7.69 & micro;A/cm2, a lower corrosion rate of 3.50 mpy, and increased barrier film resistance (97.50 Omega & centerdot;cm2) and charge-transfer resistance (1.84 k Omega & centerdot;cm2) values. These results establish a viable strategy for concurrently enhancing mechanical performance and corrosion resistance in high-strength structural steels, thereby extending their applicability in environments involving heavy mechanical loads and aggressive saline conditions.

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