目的 研究双线斑激光内送粉宽带熔覆温度场分布特性及其工艺参数对熔覆层形貌和几何特征的影响，为双线斑激光内送粉宽带熔覆在工件表面的强化、修复、改性以及宽带成形的应用提供试验与数据参考。方法 基于半椭球体热源模型，利用ANSYS软件对单道宽带熔覆过程中的熔池温度场进行数值模拟，并结合工艺试验分析离焦量、送粉速度、激光功率、扫描速度对熔覆层形貌和几何特征的影响。结果 利用半椭球体热源模型进行的数值模拟能够较为合理地反映出双线斑激光内送粉宽带熔覆过程的温度场分布，在离焦量为0 mm和负离焦量下，熔覆单道的温度分布云图均呈“带式彗星”状，熔覆层横截面上的高温区域呈现“平底形”分布，纵切面上的高温区域呈“V”形和不对称的“W”形，且两者随着深度的增加，均逐渐过渡到半椭圆形;离焦量、送粉速度、激光功率和扫描速度对熔覆层的宽度、厚度、稀释率及表面平整度都有很大的影响。结论 “带式彗星”状的熔覆单道温度分布，使得熔池前方温度梯度较大，后方温度梯度较小。横切面上“平底形”温度分布可以强化熔覆层与基体在宽度方向上的结合程度。在304不锈钢基板上熔覆KF-355金属粉末，选取离焦量为0 mm、送粉速度为45 g/min、激光功率为6 kW、扫描速度为3 mm/s的工艺参数进行熔覆试验，可以得到表面平整光滑，无明显缺陷，整体平均硬度达到645.6HV0.5的熔覆层。

As a surface engineering technology with great application potential, laser cladding technology has been widely used in the strengthening of important metal parts in aerospace, oil exploration, coal mining and other fields, which has become one of the mainstream surface functional coating preparation technologies. However, the spot size of the traditional laser cladding nozzle is too small, which affects the preparation efficiency of the coating and causes too many overlap defects in the large-area cladding. Compared with the traditional circular spot size, the existing laser wide-band cladding technology has been greatly improved, but the quality of coating preparation and powder utilization still have a lot of room for improvement. In order to change this situation, a high-power and coaxial inside-laser powder feeding wide-band cladding nozzle has been independently developed. The work aims to conduct experimental research on the temperature field distribution characteristics and the effect of process parameters on the morphology and geometric characteristics of the cladding layer based on the nozzle and provide technical reference for traditional surface modification technologies such as electroplating and thermal spraying with high pollution, high cost, low efficiency and poor bonding. Based on the parametric design language of ANSYS software, the semi-ellipsoid heat source model was selected to establish the laser cladding model with continuous moving loading of dual linear spot. The whole cladding process was simulated by the life-death element method to explore the temperature distribution characteristics of the cladding layer. The simulation results showed that the temperature distribution of laser wide-band single channel cladding process changed from "linear spot" to "banded comet" gradually, and the isotherms in front of the molten pool were dense and the temperature gradient was large. At the defocusing amount of 0 mm, the area with the highest temperature of the molten pool coincided with the loading position of the heat source. In the negative defocus state, the area with the highest molten pool temperature was located at the second spot of the dual linear spot. Whether in the state of 0 mm defocusing amount or negative defocus, the high- temperature area on the cross section of the cladding layer presented a "flat bottom" distribution, while the high-temperature area on the longitudinal section presented a "V" shape and an asymmetric "W" shape respectively, which gradually transitioned to a "semi elliptical" shape with the increase of depth. The fixed-point temperature of cladding process was measured by infrared thermometer, which verified the rationality of the model established. The effects of defocusing amount, powder feeding speed, laser power and scanning speed on the morphology and geometric characteristics of cladding layer were studied by single-factor basic process experiments and the optimal process parameters were determined as follows:defocusing amount of ?3-0 mm, powder feeding speed of 27-45 g/min, scanning speed of 1.5-3 mm/s and laser power of 5.4-6 kW. The results show that KF-355 metal powder is melted on 304 stainless steel. The "banded comet" temperature distribution of single cladding channel makes the temperature gradient in front of the molten pool larger and the temperature gradient behind smaller. The "flat bottom" temperature distribution on the cross section can strengthen the bonding degree between the cladding layer and the substrate in the width direction. When the cladding experiment is carried out with the process parameters of defocusing amount of 0 mm, powder feeding rate of 45 g/min, laser power of 6 kW and scanning speed of 3 mm/s, the cladding layer with smooth surface and no obvious defects such as cracks and holes can be obtained. The width, thickness, surface smoothness, dilution rate and cladding efficiency of the cladding layer are 39.713 mm, 0.732 mm, 0.121 mm, 0.073 and 0.43 m2/h based on the above process parameters, respectively. The average hardness of the coating area is 645.6HV0.5, which is 3.35 times higher than the average hardness of the substrate (192.9HV0.5).