Comparative Research on Fatigue Performance of High-Strength Bainitic Steel with or without Corrosion
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JMEPEG https://doi.org/10.1007/s11665-020-05207-9
Comparative Research on Fatigue Performance of High-Strength Bainitic Steel with or without Corrosion Xu Zhao, Weihua Zhang, and Hui Chen (Submitted May 5, 2020; in revised form August 27, 2020; Accepted September 19, 2020) High-strength bainitic steels have acquired a promising place among steels due to their wide applications in engineering structures. It is, therefore, worthwhile to investigate their fatigue performance in different environments. When fatigue is atmospheric, lattice strength of weaker zones including granular bainite, phase boundary and MA constituents determines the nucleation life of fatigue. The deflected microstructural short cracks enhance the early propagation life of fatigue. In lath bainite, fine ferrite laths, highdensity dislocations within the grains, small grain size and high proportion of HAGBs inhibit the crack growth process to improve propagation life of fatigue. The fracture reveals transgranular mode for propagation of fatigue. The pre-corrosion strategy is adopted before investigating corrosion fatigue process, so that there is an adequate corrosion effect on samples. The pre-corrosion time is determined to be 3 days through the analysis of electrochemical parameters, viz. corrosion potential and current. For overall fatigue life, corrosion grooves have significant deterioration effect. The transgranular and intergranular features are observed in fracture at initial stage of crack growth. Only transgranular features are found at middle and final stages. Keywords
bainitic steel, corrosion, crack behavior, fatigue performance, fracture features
1. Introduction Ultra-low-carbon bainitic steel, a type of high-strength lowalloy steel (HSLA), is widely used in several industries including building machinery, petroleum pipeline and offshore platform (Ref 1-3). The advanced thermomechanical controlled process (TMCP) followed temper operation is employed for metallurgical fabrication of this kind of steel with ultra-fine medium-temperature microstructures consisting of lath bainite (LB) and granular bainite (GB). The low strength of ferrite– pearlite steel (Ref 4, 5) and poor impact toughness of martensite steel make them unsuitable to meet the requirements (Ref 6, 7) of some engineering applications. On the other hand, the ultralow-carbon bainitic steel has excellent comprehensive mechanical properties. Whatever type of material is used, damages and failures of various types occur. The fatigue and corrosion fatigue failures are current concerns to be solved urgently. Many factors influence fatigue performance, which leads to different crack behavior and fracture features. Rementeria et al. (Ref 8) investigated the mechanism governing fatigue behavior of nanostructured bainitic steel. The microstructure and strength both have a role in determining fatigue limit. Hui et al. (Ref 9) Xu Zhao, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China; and School of Material Science and Engineering, Southwest J
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