利用数值分析和试验相结合的办法，对多道搭接激光熔覆层的开裂机理和规律进行了研究。数值分析结果表明，激光熔覆后，熔覆层内部呈明显的拉应力状态，且主要集中在熔覆层底部与基体的交界处，因此单道熔覆时熔覆层的开裂倾向主要是垂直于扫描方向。在两道搭接熔覆时，前一次熔覆输入试样的激光能量在试样内部传递和扩散已有一定的时间，试样的整体温度升高后，第二次熔覆时激光能量输入产生的热量在试样内部形成的温度梯度就会有所减小，从而降低了工件内部的应力水平。两道熔覆完成后，由于熔覆层在扫描所受的拉应力降低的幅度最大，而垂直于扫描方向所受的拉应力变化不大，此时若熔覆层开裂，则开裂的方向将不再是垂直于扫描方向，而是会与扫描方向成一定的夹角。实际熔覆中，对单道、多道熔覆时熔覆层的开裂现象进行了观察，试验结果与分析结果较好地吻合。

The mechanism and conditions giving rise to cracking during multipass laps laser cladding are investigated by finite element analysis software. Numerical analysis, combined with experimental observations, is also utilized. Calculations reveal that tensile stress is brought inside the cladding layer, and is mostly concentrated at the boundary of the substrate and the bottom of the layer. Thus, a tendency to crack takes place perpendicular to the laser scanning direction. In addition, preheating improves the process by reducing the thermal stresses in the first cladding. After cladding the parts twice, the stress of the cladding layer is decreased more rapidly than the stress of the scanning direction. Cracking is formed at a certain angle to the scanning direction. The reliability and the accuracy of the model are experimentally verified.