【作者】 卢建刚；

【导师】 李力钧；

【作者基本信息】 湖南大学 ， 机械制造及其自动化， 2004， 硕士

【摘要】 本文采用实验研究和理论分析相结合的方法对激光熔覆成形薄壁试件工艺和显微组织等方面进行了较深入系统的研究： 1．建立了一套实用的低功率激光熔覆成形实验系统，该系统由1KW连续可调CO₂激光器，三轴坐标数控精密加工机床和粉末输送系统组成，能够实现较高精度薄壁试件的激光熔覆成形。 2．对激光熔覆成形薄壁试件工艺进行了深入研究和分析，首次制得了厚度仅为0.55mm的低碳钢薄壁试件；总结出了不同工艺参数对成形过程中试件宽度的影响规律；将建立的熔池横截面积模型和实验值对比，发现二者表现出一致的变化规律，这为工艺参数的优化和制定提供了理论依据。 3．对激光熔覆成形薄壁试件的精度从实验和理论上进行了研究和分析，发现粉末喷嘴同轴度，光束模式，扫描路径，沿高度方向设定的层高以及送粉稳定性等因素对成形精度有重要影响，上述因素的变化直接影响了熔池形状尺寸及其稳定性，从而降低成形试件精度。 4．对成形后的薄壁低碳钢试件的显微组织进行分析，发现截面沿垂直扫描速度方向组织为细小的等轴晶组成，和目前文献报道的柱状枝晶组织完全不同；结合快速凝固有关理论，分析主要是因为在激光功率低，光斑直径较小等工艺参数条件下，凝固组织形成有利于等轴晶的生长方向所致；而搭接熔覆成形中碳钢组织主要是贝氏体，少量还有魏氏体组织。 5．对成形后的试件进行显微硬度和密度测试，所得结果与传统工艺方法的性能值相当，表明激光熔覆成形工艺能制作出致密度高和性能良好的试件。更多还原

【Abstract】 The process and microstructure of Laser Cladding Forming (LCF) thin parts are experimentally and theoretically studied in this paper and main conclusions are as follows:l.A practical LCF equipment, including a 1KW continuous wave CO2 laser instrument, a three-axes CNC processing table and a powder feeding system, was established, by which thin metal components with better accuracy can be built.2. The process of LCF thin wall has been studied deeply, and a 0.55 mm width thin part with lower carbon steel has been successfully built for the first time; Next, It was investigated systematically that process parameters had an influence on the width of thin wall in deposition; Finally, it was found that the experimental results, in terms of the cross section of molten pool, are in good agreement with that of the theory, which plays an important role in lying out and determining process parameters.3. The thin wall’s accuracy of LCF has also been investigated both experimentally and theoretically, it is presented that coaxial powder-feed nozzle, laser beam mode scanning path have great effects on the accuracy in LCF, for the changes of those factors have direct influences on the shape and stability of melt pool, As a result the accuracy is on the decline.4. The lower carbon steel thin wall’s microstructure of LCF has been carefully analyzed experimentally, and it’s microstructure was made up of tiny equiaxed grain, which is entirely different from that of current reports; By combining with theory of fast cooling, the main reason lies in the fact that the solidification microstructure would grow up towards equiaxed grain under lower laser power and smaller laser beam diameter; In addition, the middle carbon part’s microstructure of LCF is mainly bainite, a little is wustite structure.5.Finally, the micro-hardness and density are also examined and experimental results are close to those of traditional processes, it shows that thin parts with near densities and better properties can be fabricated using LCF.更多还原