Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched a...Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched and notched test specimens were machined from railheads of each material using electrical discharge machining （EDM） and used for the mechanical properties and fatigue evaluation respectively. Bainitic steel has the highest yield strength, ultimate strength, and strain to failure as compared to both pearlitic and austenitic manganese steels. Fatigue studies showed that the crack speed for the bainitic steel is lower than that for the pearlitie and the AM steels over the entire range of the energy release rate. The bainitic steel exhibits a higher rate of crack deceleration in the second stage, as indicated by the lower slope of the fatigue crack propagation kinetics curve in comparison with the pearlitic and manganese rail steels. This attests to the superior fatigue damage tolerance of the bainitic rail steel in comparison to pearlitic and austenitic manganese rail steels. Microstructural analysis of the three rail steels revealed that bainitic steel has a more intricate structure than AM and pearlitic steels. AM steel shows very few signs of being work hardened or toughened, which usually increases the mechanical properties of the material. As the number of alloying elements increase, the microstructure of the steel becomes more complex, resulting in the increase of mechanical properties and fatigue fracture resistance of bainitic rail steel.展开更多
文摘Microstructural analysis and fatigue crack propagation behavior of three types of rail steels, was performed. These are premium pearlitic, austenitic manganese （AM） and bainitic rail steels. Rectangular un-notched and notched test specimens were machined from railheads of each material using electrical discharge machining （EDM） and used for the mechanical properties and fatigue evaluation respectively. Bainitic steel has the highest yield strength, ultimate strength, and strain to failure as compared to both pearlitic and austenitic manganese steels. Fatigue studies showed that the crack speed for the bainitic steel is lower than that for the pearlitie and the AM steels over the entire range of the energy release rate. The bainitic steel exhibits a higher rate of crack deceleration in the second stage, as indicated by the lower slope of the fatigue crack propagation kinetics curve in comparison with the pearlitic and manganese rail steels. This attests to the superior fatigue damage tolerance of the bainitic rail steel in comparison to pearlitic and austenitic manganese rail steels. Microstructural analysis of the three rail steels revealed that bainitic steel has a more intricate structure than AM and pearlitic steels. AM steel shows very few signs of being work hardened or toughened, which usually increases the mechanical properties of the material. As the number of alloying elements increase, the microstructure of the steel becomes more complex, resulting in the increase of mechanical properties and fatigue fracture resistance of bainitic rail steel.
