铸铁轧辊表面激光强化性能研究

发布时间：2018-07-17 05:01

【摘要】：激光表面强化技术近几年在工业领域的失效零件修复方面应用很广泛。激光作为清洁能源以其能量密度大、加工效率高，修复质量好等优点越来越受到青睐。通过激光对失效零件表面进行修复或者强化，可以大大延长零件的使用寿命，为企业节省成本，节约资源。本研究采用光纤激光和CO2激光对轧辊表面进行合金化处理，对两种激光的合金化层性能进行对比分析。合金化层的合金材料为WC-6Co，其中Co元素主要起粘结WC硬质相的作用。因为所选用的WC为纳米级的细化陶瓷材料，在高能量密度的激光照射下，部分WC硬质相颗粒产生分解，，与基体材料形成复杂碳化物。未分解的WC硬质相在熔池充分混合而弥散分布在合金化层，提高了合金化层的硬度和耐磨性。首先通过大量实验，确定了轧辊激光合金化的最佳工艺参数。在最佳工艺参数条件下，采用光学显微镜、扫描电镜和X射线衍射仪等分析方法，对最佳工艺参数条件下获得的激光合金化层和热影响区的组织及相组成进行了研究分析；通过耐磨性实验，分析了合金化层的耐磨性能；利用显微硬度计对合金化层及过渡区的显微硬度和硬度分布进行了检测；通过冷热疲劳实验分析了合金化层的冷热疲劳性能。实验结果表明，光纤激光合金化层常温及高温的耐磨性能均比母材提高了3倍，CO2激光合金化层提高了2倍左右。激光合金化层硬度可达HV900，与母材相比提高了2~3倍。光纤激光合金化层深0.4mm，热影响区深度为0.6mm，总强化深度约为1mm。与光纤激光同样条件下，CO2激光合金化的总强化深度约为0.7mm。冷热疲劳实验显示，两种激光合金化层的裂纹敏感性略高于母材。两种激光合金化层的组织基本相同，由亚共晶组织组成，其中共晶组织由马氏体+复杂碳化物组成。热影响区组织由针状贝氏体和残余奥氏体、板条状马氏体、原始存在石墨球及原始存在Fe3C构成。
[Abstract]:Laser surface strengthening technology has been widely used in the field of industry in recent years. As a clean energy, laser is more and more popular because of its high energy density, high processing efficiency and good repair quality. Using laser to repair or strengthen the surface of invalid parts can greatly prolong the service life of the parts and save the cost and resources for the enterprises. In this study, optical fiber laser and CO2 laser were used to alloying the roller surface, and the properties of the alloying layer of the two kinds of laser were compared and analyzed. The alloy material of alloying layer is WC-6Co, in which Co plays the role of bonding WC hard phase. Because the WC is a fine ceramic material of nanometer size, some of the WC hard phase particles are decomposed under the laser irradiation of high energy density, forming complex carbides with the matrix material. The undecomposed WC hard phase is fully mixed in the molten pool and dispersed in the alloying layer, which improves the hardness and wear resistance of the alloying layer. Firstly, the optimum technological parameters of laser alloying of roller are determined by a large number of experiments. The microstructure and phase composition of the laser alloying layer and the heat-affected zone obtained under the optimum technological parameters were studied by means of optical microscope, scanning electron microscope and X-ray diffractometer. The wear resistance of alloyed layer was analyzed by wear resistance test, the microhardness and hardness distribution of alloying layer and transition zone were tested by microhardness meter, and the cold and thermal fatigue property of alloyed layer was analyzed by cold and hot fatigue experiment. The experimental results show that the wear resistance of the optical fiber laser alloying layer at room temperature and high temperature is 3 times higher than that of the base metal and the CO2 laser alloying layer is about 2 times higher than that of the base metal. The hardness of laser alloying layer can reach HV900, which is 3 times higher than that of base metal. The depth of fiber laser alloying layer is 0.4mm, the depth of heat-affected zone is 0.6mm, and the total strengthening depth is about 1mm. The total strengthening depth of CO _ 2 laser alloying is about 0.7 mm under the same condition as fiber laser. The cold and thermal fatigue tests show that the crack sensitivity of the two laser alloying layers is slightly higher than that of the base metal. The microstructure of the two laser alloying layers is basically the same and consists of hypoeutectic structure, in which the eutectic structure is composed of martensite complex carbides. The microstructure of the heat affected zone is composed of acicular bainite and retained austenite, lath martensite, original graphite sphere and original Fe3C.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG665

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