1 College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China 2 Guizhou Key Laboratory for Mechanical Behavior and Micro Structure of Materials, Guiyang 550025, China 3 State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Cite this article:
Yue HE,Song XIANG,Wei SHI,Jianmin LIU,Yu LIANG,Chaoyi CHEN. EFFECT OF MICROSTRUCTURAL EVOLUTION ON THE PITTING CORROSION OF COLD DRAWING PEARLITIC STEELS. Acta Metall Sin, 2016, 52(12): 1536-1544.
Heavily cold drawing pearlitic steel wires are widely used for aerospace, tire cord, suspension bridge cable, and architecture due to the high strength with acceptable level of ductility. For marine steel wires, which are widely applied in the marine and offshore structures enduring the effect of stress and corrosion, the corrosion performance is significant. Corrosion is a primary cause of structural deterioration for marine and offshore structures, which results in structural failure, leakage, product loss, environmental pollution and the loss of life. Numerous studies have been devoted to the microstructure evolution or cementite dissolution induced by cold drawing. With respect to the effect of microstructure evolution on the performance of pearlitic steel, the views were mainly focused on the mechanical performance, and only a little attention was paid to the effect of microstructure evolution on the corrosion behavior of pearlitic steel. Hence, it is still unclear whether and how the cold drawing influences the corrosion resistance of pearlitic steel. In this work, the effect of microstructure evolution on the pitting corrosion of pearlitic steel was investigated. The electrochemical measurements were carried out by electrochemical impedance spectroscopy and potentiodynamic measurement. Meanwhile, the corrosion morphology after immersion for 5 d was observed by standard visual techniques. The results indicate that corrosion resistance of cross section decreases with increasing the strain of cold drawing, while the corrosion resistance of longitudinal section decreases in the first stage of cold drawing (strain ε ≤1.2) but increases in the second step of cold drawing (ε =1.6). By characterizing the distribution of pits in the evolutionary microstructure induced by cold drawing, the grain boundary, the pearlite colony boundary and the phase boundary where the pits are inclined to initiate and propagation, are sensitive to pitting. Thus, the decrease of corrosion resistance of cross section and longitudinal section in the first stage of cold drawing (ε ≤1.2) is due to the multiplication of interface, which increases the pitting sensibility of microstructure. Electron backscattered scattering detection was used to quantify the content of <110> texture of pearlitic steels with different strains. The result showed that the improvement of corrosion resistance of the longitudinal section in the second stage of cold drawing (ε =1.6) is due to the variation of misorientation angle distribution caused by the formation of <110> texture.
Fund: Supported by National Natural Science Foundation of China (Nos.51361004, 51574095 and 51661006), Program of “One Hundred Talented People” of Guizhou Province (No.20164014), Science and Technology Project of Guizhou Province (Nos.20147-001, 20142003, 20147603 and 20152031) and Talents Foundation of Guizhou University (No.201448)
Fig.1 Cross section (a, b) and longitudinal section (c, d) Nyquist plots (a, c) of cold drawing pearlitic steels with diverse strains ε and the dependence of polarization resistance Rp and capacitance (b, d)
Fig.2 Polarization curves of cross (a) and longitudinal (b) sections of cold drawing pearlitic steels with different ε and the distribution of pits after polarization for cross section at ε =1.6 (c) and longitudinal section at ε =0.8 (d)
Fig.3 Corrosion morphologies of cross (a, c, e) and longitudinal (b, d, f) sections of cold drawing pearlitic steels at ε =0 (a, b), ε =0.8 (c, d) and ε =1.6 (e, f) after immersion for 5 d
Fig.4 Microstructure evolutions and pits distributions of cross section of cold drawing pearlitic steels at ε =0 (a, b), ε =0.8 (c, d) and ε =1.6 (e, f) (Circle with letter G represents the pit distributed in grain boundary, letter C represents the pit distributed in colony boundary, letter P represents the pit distributed in phase boundary and arrow represents the pits cluster)
Fig.5 Microstructure evolutions and pits distributions of longitudinal section of cold drawing pearlitic steels at ε =0 (a, b), ε =0.8 (c, d) and ε =1.6 (e, f)
Fig.6 EBSD inverse pole images of longitudinal section of cold drawing pearlitic steels at ε =0 (a), ε =0.8 (b) and ε =1.6 (c)
Fig.7 Statistical analysis of crystalline textures evolution of longitudinal section of cold drawing pearlitic steels
Fig.8 Statistical analysis of misorientation angle distribution of longitudinal section of cold drawing pearlitic steels
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