【摘要】 目的确定TC4钛合金激光熔覆的最优工艺参数,研究其热循环特性,分析激光熔覆温度对组织的影响规律。方法采用3D高斯热源,基于Sysweld软件平台,对TC4钛合金激光熔覆Ni60A-50%Cr₃C₂粉末过程进行数值模拟仿真,研究温度场云图及其热循环特性,模拟计算激光熔覆最高温度、加热速度和冷却速度,以及熔池最大深度和热影响区宽度,进行激光熔覆实验验证,结合熔覆层显微组织扫描电镜（SEM）图像,研究冷却速度对熔覆层组织的影响。结果由仿真可知,激光熔覆工艺参数中的光斑直径和送粉速度主要影响熔覆层的高度和宽度,对温度场分布起主要影响作用的是激光功率和扫描速度。激光功率为500 W,扫描速度为4 mm/s时,熔覆层区域熔化完全,与基体结合良好。激光熔覆最高温度为2700℃,最大加热速度约为2200℃/s,最大冷却速度约为1200℃/s,熔池最大深度在0.33～0.66 mm之间,热影响区宽度约为1.2 mm。模拟与实验得到的熔覆层截面形貌基本一致。不同冷却速度得到的熔覆层组织不同,随着冷却速度的降低,显微组织由短小的胞晶和树枝晶逐步转变为柱状晶、胞状晶和平面晶,最终形成淬火态的针状马氏体。结论最佳工艺参数为:激光功率500 W,扫描速度4 mm/s。冷却速度是影响熔覆层组织的重要因素,仿真模型的正确性及方法的可行性得到了实验验证。更多还原

【Abstract】 The work aims to determine the optimal process parameters of laser cladding of TC4 titanium alloy,study its thermal cycle characteristics and analyze the influence of laser cladding temperature on microstructure.Based on the Sysweld software platform,the numerical simulation of TC4 titanium alloy laser cladding Ni60A-50%Cr₃C₂ powder was carried out with3D Gaussian heat source.The temperature field cloud map and its thermal cycle characteristics were studied to simulate and calculate the maximum temperature,heating rate and cooling speed of laser cladding as well as the maximum depth of the molten pool and the width of the heat-affected zone,to verify by laser cladding experiments,and the scanning electron microscopy（SEM）images of the cladding layer were combined to study the effect of cooling rate on the microstructure of the cladding layer.It can be seen from the simulation that the spot diameter and the powder feeding speed in the laser cladding process parameters mainly affected the height and width of the cladding layer.The main influence factors of the temperature field distribution were the laser power and scanning speed.When the laser power was 500 W,and the scanning speed was 4mm/s,the cladding layer was completely melted and well bonded to the substrate;when the maximum temperature of laser cladding was 2700℃,the maximum heating rate was about 2200℃/s,the maximum cooling rate was about 1200℃/s,the maximum depth of the molten pool was between 0.33 mm and 0.66 mm,and the width of the heat-affected zone was about1.2mm;the cross-section morphology of the cladding layer obtained by the simulation and experiment was basically the same;the microstructure of the cladding layer obtained by different cooling rates was different,and the microstructure was composed of short cell crystals as the cooling rate decreased.And the dendrites gradually transformed into columnar crystals,cell crystals and planar crystals,and finally formed quenched acicular martensite.The optimum process parameters are laser power of 500 W and scanning speed of 4 mm/s.The cooling rate is an important factor affecting the microstructure of the cladding layer.The correctness of the simulation model and the feasibility of the method are verified by experiments.更多还原