Utilization of laser powder deposition (LPD) as an innovative repair tool for damaged steel components is increasingly growing in recent years. This paper investigates repairing a standard US light rail using LPD. No study has focused on repairing standard US rails thus far. Besides, this is the first time that a three-dimensional finite element model is developed where element-birth-and-kill technique is employed to study thermal-kinetic-mechanical evolutions during the LPD rail repair process. Exploration of hardness versus microstructure yielded a reverse correlation between hardness level and austenite volume fraction. The maximum hardness was found near rail-deposition interface with the minimum austenite concentration, while the topmost deposition layer with the highest austenite concentration showed the minimum hardness. Longitudinal residual stresses at the rail-deposition interface were significantly more than that of transversal and normal. Comparing the residual stress against deposition material yield strength showed a slight exceedance (~5%) of transversal stress from the maximum limit, no exceedance for normal stress, but an extreme exceedance of 50% for longitudinal stress. This fact suggested a high risk of cracking along longitudinal direction at the rail-deposition interface, while there existed only a minor risk of transversal cracking and almost no chance of layer delamination. The simulated results were compared against experimental results obtained via optical and scanning electron microscopy, hardness test, and X-ray diffraction stress measurement, where a maximum deviation of 10% proved the model accuracy. The validated model in this study would be a great backbone for future studies on different process parameters to increase hardness and reduce stress in an LPD repaired rail.

近年来，激光粉末沉积 (LPD) 作为一种创新的受损钢部件修复工具的使用越来越多。本文研究了使用 LPD 修复标准美国轻轨。迄今为止，还没有研究专注于修复标准的美国铁路。此外，这是首次建立三维有限元模型，利用单元生灭技术研究LPD钢轨修复过程中的热-动力学-力学演化。对硬度与微观结构的探索发现硬度水平与奥氏体体积分数之间存在反向相关性。在铁轨-沉积界面附近发现硬度最大，奥氏体浓度最低，而奥氏体浓度最高的最上层沉积层硬度最低。钢轨-沉积界面的纵向残余应力明显大于横向和法向残余应力。将残余应力与沉积材料屈服强度进行比较，发现横向应力比最大极限略有超过 (~5%)，法向应力没有超过，但纵向应力却极端超过 50%。这一事实表明，在钢轨-沉积界面沿纵向开裂的风险很高，而横向开裂的风险很小，几乎没有分层的机会。将模拟结果与通过光学和扫描电子显微镜、硬度测试和 X 射线衍射应力测量获得的实验结果进行比较，其中 10% 的最大偏差证明了模型的准确性。