| 引用本文: | 丁昊昊,谢天星,王文健,祝毅,阳义,郭俊,林强.钢轨材料局部激光熔覆自熔性合金涂层的磨损与滚动接触疲劳行为[J].中国表面工程,2024,37(3):1~13 |
| DING Haohao,XIE Tianxing,WANG Wenjian,ZHU Yi,YANG Yi,GUO Jun,LIN Qiang.Wear and Rolling Contact Fatigue Behavior of Locally Laser Cladded Rail Material Using Self-fusible Alloy[J].China Surface Engineering,2024,37(3):1~13 |
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| 钢轨材料局部激光熔覆自熔性合金涂层的磨损与滚动接触疲劳行为 |
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丁昊昊1，谢天星1，王文健1，祝毅2，阳义3，郭俊1，林强1
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1.西南交通大学轨道交通运载系统全国重点实验室 成都 610031 ；2.浙江大学流体动力与机电系统国家重点实验室 杭州 310027 ；3.成都青石激光科技有限公司 成都 610213
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| 摘要: |
| 激光熔覆技术可用于钢轨局部损伤表面的局部修复，但局部修复钢轨材料的磨损与滚动接触疲劳损伤规律尚不清楚。 通过在钢轨试样表面切除凹槽来模拟局部损伤，在凹槽处激光熔覆 Ni 基、Fe 基和 Co 基自熔性合金粉末，分析修复钢轨微观组织与硬度，然后利用双轮对滚试验研究局部修复钢轨试样的磨损与滚动接触疲劳行为。结果表明，激光熔覆涂层形成了共晶与枝晶组织，Ni 基涂层组织粗大、硬度较小，Fe 基与 Co 基涂层组织尺寸较小，Fe 基涂层硬度最大，Co 基涂层硬度居中。 相比未熔覆区域，激光熔覆区（涂层）塑性变形层厚度较小，且涂层原始硬度越高，硬化后硬度越大，但硬化率和硬化层厚度更小。未熔覆区滚动接触疲劳裂纹较长，但裂纹角度较小；熔覆区裂纹长度均有所降低，但裂纹扩展角度明显增大；熔覆区与未熔覆区结合处疲劳损伤最为严重，疲劳裂纹角度和深度均比熔覆区和未熔覆区更大。对比分析发现，Stellite 21（Co 基）熔覆试样摩擦因数较低，熔覆区与未熔覆区磨损深度差较小，抗滚动接触疲劳性能较好，较为适合钢轨局部损伤的激光修复。研究结果可为激光熔覆技术在钢轨局部修复上的应用与优化提供理论与技术指导。 |
| 关键词: 激光熔覆 损伤钢轨 微观组织 磨损 滚动接触疲劳 |
| DOI：10.11933/j.issn.1007-9289.20230830002 |
| 分类号:TH117 |
| 基金项目:国家自然科学基金（52205578, 52320105007）；四川省区域创新合作项目（2022YFQ0113）；中央高校基本科研业务费专项（2682024CG007） |
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| Wear and Rolling Contact Fatigue Behavior of Locally Laser Cladded Rail Material Using Self-fusible Alloy |
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DING Haohao1，XIE Tianxing1，WANG Wenjian1，ZHU Yi2，YANG Yi3，GUO Jun1，LIN Qiang1
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1.State Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong University,Chengdu 610031 , China ；2.State Key Laboratory of Fluid Power and Mechatronic Systems,Zhejiang University, Hangzhou 310027 , China ；3.Chengdu Qingshi Laser Technology Co., Ltd., Chengdu 610213 , China
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| Abstract: |
| With an increase in the axle load of trains, damage to the rails becomes more severe, decreasing their service life. Thus, local repair could be a solution for rail surface damage. Laser cladding is a relatively new additive manufacturing technology that can be used for local damage repair. However, wear and rolling contact fatigue (RCF) damage behaviors, particularly the damage at the boundary between the clad and unclad zones, have not been thoroughly explored. Thus, a pothole is cut off from the U75V rail sample (a roller sample) to simulate the local damage on the rail. Ni-, Fe-, and Co-based self-fluxing alloy powders (F103, Fe-Cr, Fe-58, Stellite 21, Stellite 22, and Stellite 23) are laser cladded at the pothole using a CO2 laser with a rectangular spot size of 7 mm × 1 mm, a laser power of 1.9 kW, a scan speed of 200 mm / min, and a powder feed rate of 15 g / min. The microstructure and hardness of the locally repaired rail materials are analyzed. The wear and RCF behaviors of the laser-repaired rail samples are studied using the twin-disc rolling test with a maximum contact pressure of 1.1 GPa, a slip ratio of 0.75%, and a rotational speed of 500 r / min. The number of cycles for each rolling test is 105 . The friction coefficient, wear rate, depth, plastic deformation, and damage morphology are analyzed. The results showed that the cladded sample could be divided into three regions in the depth direction on the cross section or in the rolling direction on the surface: the clad zone, heat-affected zone, and substrate. Fine eutectic and dendritic structures are formed in the laser cladding. The hardness is higher than that of the substrate. The microstructure of the Ni-based clad is coarse, and its hardness is low. The microstructural sizes of the Fe-and Co-based clads are small. The hardness of the Fe-based clads is high and that of the Co-based clads has an intermediate value. During the rolling test, the friction coefficient exhibits an increasing trend during the running-in period and then remains stable. The stable friction coefficient is approximately 0.4 and shows no evident difference for samples with different clads. After the rolling test, the wear rates of the samples with Ni-and Fe-based clads are high, and those of the samples with Co-based clads are low. The wear depth in the clad zone is smaller than that in the unclad zone. The surface hardness of the samples is increased after testing, and plastic deformation of the microstructure is observed in the cross section. Compared with the uncoated zone, the thickness of the plastic deformation layer in the laser cladded zone (that is, clads) is smaller. With an increase in the original hardness of the cladding, the hardness after testing is increased; however, the hardening ratio and plastic deformation layer thickness are decreased. The damage mode of the laser-repaired rail is predominated by fatigue wear. In the unclad zone, the RCF crack length is large whereas the crack angle is small. In the clad zone, the crack length is decreased whereas the crack angle is increased. The RCF damage at the boundary between the clad and unclad zones is the most severe. The crack angle and depth at the boundary are greater than those in the clad and unclad zones. Comparing the six studied clads, notably, the Stellite 21 (Co-based) cladded sample presents a lower friction coefficient, smaller wear depth difference between the cladded and uncladded zones, and better RCF resistance, making it more suitable for laser repair of local rail damage. The research results can provide theoretical and technical guidance for the application and optimization of laser cladding technology for local rail repair. |
| Key words: laser cladding damaged rail microstructure wear rolling contact fatigue |
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