为了减少激光熔覆技术中因温度梯度大而产生的熔覆层裂纹,在激光熔覆过程中采用预热基体的方法来减小温度梯度。采用ANSYS软件建立45#钢基材上激光熔覆镍基金属粉末的多道搭接温度场有限元模型,通过热电偶测温验证模型的可靠性,利用建立的有限元模型分析熔覆层在熔覆过程中熔覆层边缘的温度梯度变化规律以及基材预热温度对熔覆层温度梯度的影响。结果表明,最大温度梯度位于熔覆层与基体结合界面的边缘,使得此处成为金属熔池凝固的极端条件,导致此处极易产生裂纹；在基材预热为200℃时,可以显著降低熔覆层凝固过程中的温度梯度,温度梯度的降低越明显,越能有效地抑制裂纹产生。通过模拟与实验的结合为实际激光熔覆制造提供了切实可行的参考依据。

In order to reduce cracks in cladding layers caused by large temperature gradient in laser cladding technology, preheated matrix in laser cladding process was used to reduce temperature gradient. The finite element model of multi-lap temperature field of laser cladding nickel-based metal powder on 45# steel substrate was established by using ANSYS software. The reliability of the model was verified by thermocouple temperature measurement. Temperature gradient of cladding layer on the edge of cladding layer during the cladding process and the effect of the preheating temperature of the substrate on temperature gradient of cladding layer were analyzed by the finite element model. The results show that the maximum temperature gradient is located at the edge of the bonding interface between the cladding layer and the substrate. It is an extreme condition for the solidification of the metal molten pool and causes the crack to be easily produced here. With preheating temperature of 200℃, the substrate preheating can significantly reduce the temperature gradient during the solidification process of the cladding layer, and the decrease of the temperature gradient is more obvious, which can effectively inhibit the crack generation. The combination of simulation and experiment provides a practical reference for the actual laser cladding manufacturing.