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首页> 外文期刊>Materials Science and Engineering >High/very high cycle fatigue behaviors of medium carbon pearlitic wheel steels and the effects of microstructure and non-metallic inclusions
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High/very high cycle fatigue behaviors of medium carbon pearlitic wheel steels and the effects of microstructure and non-metallic inclusions

机译：中碳珠光体车轮钢的高/超高循环疲劳行为以及显微组织和非金属夹杂物的影响

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摘要

The high cycle fatigue (HCF) and very high cycle fatigue (VHCF) behaviors of medium carbon pearlitic wheel steels were investigated by the combination of conventional tension-compression fatigue test (up to 10(8) cycles, frequency of 150 Hz) and ultrasonic fatigue test (up to 10(9) cycles, frequency of 20 kHz). In the S-N curves, fatigue limit plateaus were found in the range of 10(7)-10(8) cycles for the conventional fatigue test and in the range of 10(8)-10(9) cycles for the ultrasonic fatigue test. No fatigue failures were found in the VHCF regime. The fatigue fractures were mainly originated from the surface matrix of specimens, and a small amount of fracture origins were the surface/subsurface inclusions or internal inclusions. Only oxide inclusions were found to cause fatigue fracture, while crack initiation was not found to be associated with sulfides in this work. The effects of pearlite block size and inclusion size on the fatigue strength were discussed based on the Murakami model. The fatigue limit was slightly improved by the grain size refinement, but was insensitive to inclusions. The main reason was that the sizes of most inclusions in the tested steels were smaller than the critical size, below which fatigue failure can hardly occur from inclusions. When most of the oxides were enveloped in sulfides, the fatigue properties, however, were not obviously improved. This is because the sizes of those oxides encapsulated by sulfides were substantially smaller than the critical inclusion size, while large-sized oxides were not found to be encapsulated by sulfides. Compared to the conventional high strength steels with the tensile strength beyond 1200 MPa, the lower sensitivity of fatigue behavior to inclusions was found in the studied steels, mainly due to the larger critical inclusion sizes.
机译：通过常规拉伸-压缩疲劳试验（高达10（8）个循环，频率为150 Hz）与超声波相结合，研究了中碳珠光体车轮钢的高循环疲劳（HCF）和超高循环疲劳（VHCF）行为。疲劳测试（最多10（9）个周期，频率为20 kHz）。在S-N曲线中，对于常规疲劳试验，疲劳极限平稳期在10（7）-10（8）个循环的范围内，对于超声疲劳试验，在10（8）-10（9）个循环的范围内。在VHCF方案中未发现疲劳失效。疲劳断裂主要起源于试样的表面基体，少量断裂起源于表面/亚表面夹杂物或内部夹杂物。在这项工作中，仅发现氧化物夹杂物引起疲劳断裂，而未发现裂纹萌生与硫化物有关。基于村上模型，讨论了珠光体块尺寸和夹杂物尺寸对疲劳强度的影响。通过细化晶粒尺寸可以稍微改善疲劳极限，但是对夹杂物不敏感。主要原因是被测钢中大多数夹杂物的尺寸小于临界尺寸，低于临界尺寸时，夹杂物几乎不会发生疲劳破坏。当大多数氧化物包裹在硫化物中时，疲劳性能并未得到明显改善。这是因为被硫化物包封的那些氧化物的尺寸基本上小于临界夹杂物尺寸，而没有发现大尺寸的氧化物被硫化物包封。与拉伸强度超过1200 MPa的常规高强度钢相比，在研究的钢中发现疲劳行为对夹杂物的敏感性较低，这主要是由于较大的临界夹杂物尺寸所致。

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