Page 118 - 《摩擦学学报》2021年第6期

第 6 期 刘旭东, 等: 原始组织对ER9车轮钢滚动接触疲劳性能的影响 903

backscatter diffraction (EBSD) to observe and analyze the surface morphology, surface microstructure and cross-
sectional microstructure of two different original microstructure samples. Analyze the reasons for the difference in
fatigue life of the two samples before and after pre-wear. Results: According to the principle of colloidal equilibrium,
lamellar cementite is easier to dissolve. During machining, due to the interaction of cutting force and cutting heat, The
original P+PF sample will form a machined fine-grain layer, which is unevenly distributed on the surface of the sample,
the maximum thickness is about 1 μm, while the original TS sample has no obvious fine-grain layer. Due to the
existence of the machined fine-grain layer, the rolling contact fatigue life of the two different original microstructure
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samples is quite different. Rolling contact fatigue life of original P+PF sample and original TS sample are 1.6×10 cycles
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and 5.6×10 cycles, respectively. Observe the cross-sectional microstructure and cracks of the two samples after the
same cycle of rolling contact fatigue test. The P+PF sample will preferentially form shallow spalling, and rolling contact
fatigue cracks will be induced on the basis of shallow spalling, while the TS sample will Rolling contact fatigue cracks
with an angle of 45° to the surface are directly formed. As the number of operating cycles increases, the length of fatigue
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cracks continues to grow. When pre-wearing two samples with different original microstructures for 1×10 cycles, the
surface of the P+PF sample was dominated by adhesive wear, and there was a slight fatigue wear characterized by scaly
skin. While TS sample the form of wear is adhesive wear. Observing the cross-sectional microstructure of the sample at
this time, both the P+PF sample and the TS sample showed a fine-grained layer due to the plastic deformation of the
sample surface under the action of the contact stress. The surface hardness of the two samples has been greatly
improved. The P+PF sample has a better surface hardening ability. Pre-wear causes the surface of the sample to be
strengthened, which improves the rolling contact fatigue life under oil lubrication conditions.In the subsequent rolling
contact fatigue test, two different original microstructure ER9 wheel steel samples all showed the shallow exfoliation of
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the fine-grained layer.After pre-wear, the rolling contact fatigue life of the P+PF sample and TS sample was 2.7×10
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cycles and 8.3×10 cycles, respectively. Conclusion: During the fatigue test, the original P+PF sample will preferentially
initiate shallow cracks on the surface, shallow cracks propagate in the fine-grained layer to form shallow spalling, and
fatigue cracks are induced in the area where the fine-grained layer spalls. On the other hand, rolling contact fatigue
cracks initiated directly after short cycles of operation of the original TS sample. Therefore, the original P+PF sample
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has better resistance to fatigue crack initiation. After pre-wear 1×10 cycles , a small amount of fatigue wear cracks were
formed on the surface of the P+PF sample, and some of the fatigue wear cracks became the crack source of rolling
contact fatigue cracks. In addition, the surface hardness of the pre-wear P+PF sample is higher and more fragile, and the
initiation of fatigue cracks are easy to propagate. However, due to the refinement of the surface layer of the sample,
which effectively resists the initiation of cracks, the fatigue life is increased by 1.7 times compared with the original
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P+PF sample. After pre-wear 1×10 cycles, the TS sample did not show fatigue wear cracks. At the same time, due to the
surface strengthening caused by the pre-wear, the fatigue life of the TS sample was 15 times longer than that of the
original TS sample, and was higher than the same cycle of pre-wear 3 times of P+PF sample.
Key words: ER9 wheel steel; lamellar pearlite; tempered sorbite; cracks; fine-grained layer; pre-wear

滚动接触疲劳是列车轮轨的主要失效形式，全球 良好的耐磨性一直被广泛应用于车轮材料，但是由于
铁路行业的主要问题之一就是滚动接触疲劳所引发 珠光体钢中片层状渗碳体的溶解和断裂增强了表面
[6]
的车轮和钢轨的损伤，造成的损坏可能使得轨头剥落 硬度，加速了棘轮破坏 ，而且在磨损过程中，珠光体
[1]
或轨道完全失效 . 近年来，随着铁路运输的发展，客 钢易在表面形成白层(WEL)，与塑性变形层相比，WEL
运列车的速度不断提升，使得铁路运营环境更加恶 具有更高的硬度，珠光体钢的WEL也是形成疲劳裂纹
[7]
化，伴随来的滚动接触疲劳现象就越发严重 [2-3] . 的主要部位 . 且由于珠光体和铁素体之间的应变分
轮轨材料在实际运行过程中，在干摩擦条件下会 配，珠光体车轮钢的疲劳裂纹主要在珠光体与先共析
[8]
形成一定深度的梯度变形层，在液体润滑条件下，梯 铁素体的界面处萌生并扩展 ，相关学者的研究结果
度变形层将不可避免地影响轮轨材料的滚动接触疲 也表明，微观结构不均匀也会导致滚动接触疲劳裂纹

劳寿命 [4-5] . 因此，研究车轮钢在预磨损前后的滚动接 的形成 [9-10] . 故改善原始微观组织均匀性对于改善轮
触疲劳性能有重要的意义. 轨材料的滚动接触疲劳寿命有着重要的作用.
珠光体钢由于高强度、良好的加工硬化性能以及 本文作者对片层状珠光体车轮钢采用调质处理，