激光熔覆涂层中原位生成TaC的颗粒行为特征  

Particle Behavior of in-situ Synthesized TaC in Laser Clad Coating

作　　者：余廷[1] 邓琦林[1] 郑静风 董刚[3] 杨建国[1] 

机构地区：[1]上海交通大学机械与动力学院,上海200240 [2]延锋伟世通汽车模具有限公司,上海201206 [3]同济大学材料科学与工程学院,上海200092

出　　处：《中国激光》2011年第7期101-106,共6页Chinese Journal of Lasers

基　　金：国家自然科学基金(50675136)资助课题

摘　　要：通过激光在中碳钢基体表面熔覆NiCrBSi+Ta复合涂层原位生成了TaC颗粒。利用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析涂层的形貌、成分和物相。讨论了TaC颗粒的形貌、生长机制、分布情况以及影响颗粒分布的因素。结果显示,TaC颗粒为等轴或花瓣状,其形成机制主要是独立形核生长、碰撞烧结和原位析出。TaC颗粒分布均匀,没有出现明显的梯度分布现象。TaC颗粒被基体相晶界捕获而不是被基体相吞没或推至涂层顶部,这促使颗粒均匀分布。TaC颗粒周围生长有针状铬的硼化物或碳化物,应有利于颗粒与基体牢固结合。不同于其他碳化物的是,研究发现TaC颗粒中固溶了大量的Si元素,这为控制陶瓷颗粒强化材料中的Si含量提供了一种新途径。NiCrBSi＋Ta composite coating is produced on surface of a medium carbon steel substrate by laser cladding in order to in situ synthesize TaC particle.Scanning electron microscope（SEM）,energy-dispersive spectrometer（EDS） and X-ray diffractometer（XRD） are used to observe and analyze the coating.Morphology,distribution and formation mechanism of in situ synthesized TaC particle are discussed.In spite of high melting point,equiaxial and flower-like TaC particles are still formed by one-step laser cladding.The result shows that the formation mechanism of TaC particle is nucleation and growth,colliding and sintering,and in situ precipitating.The distribution of particles is homogeneous.Most of TaC particles are entrapped at grain boundaries instead of being engulfed by matrices or pushed to the top of the coating due to high convection,high thermal gradient,multidirectional solidification of matrix dendrites and difference between thermal conductivities of particle and matrix.The entrapment at grain boundaries is favorable for the homogeneous distribution of particles.Acicular chromium borides or carbides are found to grow up around boundaries of TaC particles,which will be beneficial for cohesion strength between particle and matrix.High amount of Si element dissolved in in-situ synthesized TaC particles is also found as compared to other carbides such as TiC,which will supply a new method to control the Si content in ceramic particle strengthening materials.

关 键 词：激光技术 激光熔覆 原位生成 碳化钽 颗粒行为 硅 

分 类 号：TG156.99[金属学及工艺—热处理]