中文摘要：

利用有限元分析软件SYSWELD建立了三维有限元模型，对不同预热温度下激光熔覆铁基涂层的过程进行了数值模拟，分析了不同预热温度下温度场和组织转变的变化规律，研究了冷却速度和组织转变对残余应力场的影响。结果表明，预热温度越高，熔覆层中心的峰值温度越高，同时能有效降低熔覆层冷却速度。预热温度在20-300℃范围内时，随着预热温度的增加，熔覆层贝氏体含量逐渐增加，铁素体和马氏体含量逐渐减少，使得熔覆层残余应力增大；预热温度高于300℃以后，随预热温度增加冷却速度显著降低，组织中铁素体含量逐渐增加，贝氏体含量逐渐减少，残余应力随之减小。

英文摘要：

In this paper, a 3-D finite element model was established by means of a finite element code--SYSWELD. The laser cladding process of iron-based coatings was simulated and the change rules of temperature field and microstructural transformation were analyzed both under different preheating temperatures. The effects of cooling rate and microstructural transformation on residual stress field are also studied. The results show that the higher the preheating temperature is, the higher the peak temperature of the cladding center is, which will reduce the cooling rate. When the preheating temperature is at the range of 20 ℃ to 300 ℃, with the increasing of it, the content of bainite in cladding layer increases and the content of ferrite and martensite decreases gradually which result in the increase of residual stress. However, when the preheating temperature is above 300 ℃, with the increasing of it, the cooling rate decreases sharply, the content of ferrite in cladding layer increases and the bainite decreases, which bring out the decrease of the residual stress gradually.