Tempering Temperature‐Induced Microstructural Evolution and Corrosion Resistance of Laser Quenched 40CrNiMoA Steel

ABSTRACT Tempering temperature (TT) played a critical role in regulating the microstructure and electrochemical corrosion behavior of laser quenched steels. In this study, laser quenched 40CrNiMoA steel was tempered at 130, 150°C and 170°C, and the effects of TT on the microstructure, oxide‐product stability and corrosion behavior of laser quenched 40CrNiMoA steel in 3.5% NaCl solution were systematically investigated. The results show that the tempering promotes the microstructural homogenization while retaining the refined martensitic structure, and the 130°C‐tempered sample exhibits the lowest corrosion current density of 5.778 × 10 −6 A·cm −2 , the highest polarization resistance of 4572 Ω·cm 2 and the highest charge‐transfer resistance of 1995 Ω·cm 2 among the three kinds of tempered samples. This improved corrosion performance is attributed to the synergistic effects of microstructural stabilization and suppression of Cl − penetration by the compact oxide‐product film, which provides guidance for optimizing the TT of laser‐quenched 40CrNiMoA steel for corrosion‐resistant applications.