Effect of hydrogen on tensile and ultra-low cycle fatigue properties of 30CrMo steel
The influence of hydrogen on the ultra-low cycle fatigue performance and mechanical behavior of 30CrMo steel was investigated in this study.The experimental steel was subjected to electrochemical hydrogen charging in a 0.5 mol/L H2 SO4 solution for 1 and 4 h,respectively,subsequently,ultra-low cycle fatigue tests and tensile tests were carried out under simulated earthquake load-controlled axial by displacement to obtain cyclic stress-strain responses,hysteresis behavior,and strain-life relationships.Combining with scanning electron microscope(SEM),fracture surface morphology was observed to analyze the ultra-low cycle fatigue fracture mechanism.The results show that the tensile strength of the experimental steel increases from 681 MPa to 689 and 698 MPa after 1 and 4h hydrogen filling;the fracture elongation has decreased from 33%to 29%and 19%,and the reduction in ductility becomes more severe with higher hydrogen concentration.Electrochemical hydrogen charging significantly weakens the fatigue resistance of the experimental steel.The fatigue life of the test material decreased by 33.8%to 40.7%and 65.3%to 69.8%after pre-charging with hydrogen for 1 and 4h,respectively.Hydrogen charging had no significant impact on the cyclic response characteristics of the experimental steel in relation to Masing behavior.Prolonged hydrogen charging reduced the crack propagation zone area and accelerated the crack propagation rate of the 30CrMo steel.
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