铁路车轴表面强化技术研究与应用

车轴是列车转向架的核心部件之一，引发车轴失效的表面损伤形式主要包括腐蚀、微动磨损和外物致损。表面强化可改善车轴表面完整性，进而抑制裂纹萌生和延缓裂纹扩展，以提高车轴疲劳强度并延长剩余寿命。车轴表面强化技术主要包括滚压、喷丸及表面感应淬火。首先，概述了国内外普速和高速列车车轴表面强化技术的基本原理:滚压和喷丸等物理强化方式使车轴表面塑性变形硬化并引入残余压应力，表面感应淬火通过马氏体相变提高车轴表面强度并引入残余压应力。然后，重点综述了上述3种表面强化技术的研究进展及其在当前车轴制造过程中的应用，其中，深度滚压是车轴表面强化的主要方式，表面感应淬火主要应用于部分高铁车轴上，而喷丸在车轴上的应用尚少。最后，从经济性和安全性的角度对比了车轴表面强化技术的优劣:喷丸强化深度有限，不足以提高车轴剩余寿命;中碳钢车轴表面淬火方案在淬硬层深度和残余应力大小方面均优于合金钢车轴滚压方案。基于损伤容限设计的评价为未来车轴表面强化技术的研究和应用提供了借鉴。

Research and Application of Surface Hardening Techniques on Railway Axles

Axle is a critical component of the train bogie. Surface defects that cause axle failures include corrosion, fretting wear and flying ballast impact damage. Surface integrity of axles can be improved by surface hardening to inhibit the initiation of surface cracks and slow down the propagation of surface cracks. As a result, the fatigue strength of axles is raised and the remaining life is extended. Surface hardening techniques of axles used in general speed and high-speed trains home and abroad including rolling, shot peening and induction hardening and their hardening mechanisms are summarized in this paper. Physical strengthening methods such as shot peening and rolling draw on plastic deformation strengthening and impart of residual compressive stress. Surface induction hardening improves the surface strength of axles by martensitic transformation and introduction of residual compressive stress. A comprehensive overview on the research and application of the above three axle surface hardening techniques in current axle manufacturing is given. Wherein, deep rolling is the dominant surface hardening technique for axles and surface induction hardening is utilized in small percent of high-speed train axles, while shot peening is less employed in axles manufacturing. Finally, the advantages and disadvantages of three axle surface hardening techniques are compared from perspective of economy and safety. The hardening depth of shot peening is not sufficient to prolong axle remaining life. From the point of hardening depth and residual stress magnitude, the hardening scheme of medium carbon steel axles is superior to that of alloy steel axles. Damage tolerance-based assessment provides guidance to the study and utilization of axle surface hardening techniques in the future.