目的 研究不同厚度涂层的再制造零件在弯曲疲劳情况下的失效形式。方法 利用电弧喷涂对零件进行再制造处理，并进行四点弯曲疲劳实验，利用扫描电镜对不同厚度涂层的再制造零件断口形貌进行观察，研究不同厚度涂层的疲劳裂纹萌生、扩展以及断裂方式。结果 疲劳裂纹萌生形式主要为多源疲劳失效，在疲劳裂纹的扩展过程中，不同平面内扩展的裂纹相交，形成了台阶形貌。当涂层厚度为100、200 μm时，裂纹主要萌生于四点弯曲实验中应力最集中的部位，萌生于涂层和基体之间，并逐渐地向涂层和基体扩展，直至试样断裂。而涂层厚度为300、400 μm时，裂纹萌生部位主要集中于四点弯曲疲劳试验中应力最大部位的两侧，并呈对称式分布，裂纹在界面处连接，使得涂层和基体产生分层现象，之后分层部位处裂纹沿着基体方向扩展，直至试样断裂。结论 涂层厚度不同，整个系统的失效模式也不同。对于较薄的涂层，裂纹模式主要为垂直于涂层-基体界面的裂纹，此时拉伸失效占主导。对于较厚的涂层，界面裂纹为主要的裂纹模式，此时剪切失效占主导。

The work aims to study different failure forms of remanufactured parts with different thickness of coatings in four-point bending fatigue test. The parts were remanufactured by performing arc spraying and then four-point bending test was performed. Fracture morphology of the remanufactured parts with different thickness of coatings was observed with scanning electron microscope, and initiation, growth and fracture mode of fatigue cracks on different thickness of coatings were studied. Initiation form of the fatigue cracks was found to be mainly multi-source failure fatigue. In the growth process of fatigue cracks, fatigue cracks growing in different planes intersected and formed shape of steps. When coating thickness was 100 μm and 200 μm, crack initiation mainly occurred between the coating and substrate in position bearing the most concentrated stress in the four-point bending test. And the cracks gradually expanded to the coating and substrate until the sample fractured. When coating thickness was 300 μm and 400 μm, crack initiation mainly occurred on both sides of the position bearing the maximum stress in the four-point bending test. The cracks spread symmetrically, connected on interface and led to layering of the coating and substrate. Later cracks in layered positions grew along the direction of substrate until the sample fractured. Failure mode of the whole system varies with coating thickness. For thin coatings, crack mode is mainly cracks perpendicular to coating-substrate interface, and tension failure dominates. For thick coatings, crack mode is mainly interface crack, and shear failure dominates.