【作者】 杨光辉；

【导师】 刘衍聪；

【作者基本信息】 中国石油大学(华东) ， 机械工程， 2015， 硕士

【摘要】 利用激光熔覆技术在灰铸铁零件表面制备特殊的涂层,可以显著的提高零件的表面性能。激光熔覆涂层的结合状态是影响其结合强度主要方面,进而影响熔覆涂层的应用。现有的研究大多集中在激光熔覆涂层的表面特性,而对其结合状态的研究比较少。结合区作为激光熔覆涂层与灰铸铁基体相连接的中间部分,在灰铸铁零件服役过程中往往容易萌生裂纹并扩展,导致熔覆涂层失效。本课题以激光熔覆涂层结合区的微观组织特性和某些宏观力学性能为研究目标,深入研究结合区的微观组成相及其组织缺陷、剪切强度对其结合状态的影响规律。主要研究内容如下所示。依据传热学原理和激光热作用机理,采用非线性热-结构耦合的方法,建立激光熔覆涂层的有限元模型,研究结合区在激光熔覆过程中的温度场和应力场变化。根据温度场结果研究结合区的微观组织变化机理,根据应力场结果研究结合区微裂机理和残余应力机理。进行激光熔覆实验,对结合区的组织变化机理和微裂机理的模拟分析结果做验证,并确定结合区微观组织组成,研究各相组织对微观组织强度的影响机理,得出结合状态的微观影响机理,并将微观影响因素参数化。研究现存的涂层结合强度测试方法对于激光熔覆涂层的适用性,选择合适的结合强度测试方法,根据激光熔覆涂层的特性对方法进行改进研究,对激光熔覆涂层在结合强度测量方法下的应力场进行模拟分析研究,并通过模拟结果对激光熔覆试样进行结构上的改进,探寻在结合强度测量方法下比较优越的熔覆涂层结构机制。设计制造激光熔覆涂层结合强度测量的实验夹具,根据结合强度测量过程中的夹具的应力场模拟结果确定其热处理工艺。设计激光熔覆涂层结合强度实验,探究激光熔覆涂层的结合强度的数量级,得出激光熔覆涂层结合状态的微观和宏观综合影响机制。更多还原

【Abstract】 Utilizing laser cladding technology to prepare special coating in the surface of gray cast iron parts can significantly improve the surface performance of parts.The bonding state of the laser cladding coating is a main aspect affecting the bond strength,and then it can influence the application of laser cladding coating.Most of the existing research focus on the surface features of laser cladding coating,but there is little research about its bonding state.As the middle part between the laser cladding coating and the gray cast iron substrate,bonding area is tend to initiate and extend cracks in the process of gray cast iron parts service,and then it led to the cladding coating failure.The research work in this dissertation aims at microstructure features and some macro mechanical properties of bonding area of laser cladding coating.The influence law of microscopic composition and microstructure defects and shear strength of bonding area to its bonding state is analyzed profoundly.The main research contents are as follows.Based on theory of heat transfer and the mechanism of laser thermo effect,using the nonlinear thermal-mechanical indirect coupling method,a numerical model of laser cladding coating is established to analyze the changing of temperature field and stress field of bonding area in the process of laser cladding.According to the result of temperature field and stress field,the mechanism of microstructure changes and micro crack and residual stress is analyzed.Laser cladding process is carried out to verify the simulation results of the mechanism of microstructure changes and micro crack of bonding area,and determine the microstructure of bonding area.The influence mechanism of microstructure strength by each phase organization is analyzed to conclude the microcosmic influence mechanism of bonding area of laser cladding coating,and parameterized the microcosm influence factors.The existing coating bond strength testing method for the applicability of the laser cladding coating is analyzed,and appropriate bond strength testing methods according to the characteristics of laser cladding coating is selected and improved.The stress field of laser cladding coating under bond strength testing methods is analyzed to improve the structure of laser cladding coating specimens,and conclude the microcosmic influence mechanism of bonding strength.The design and manufacture of laser cladding coating bond strength measurement of experimental fixture is researched.According to the results of stress field simulation of the bonding strength measuring fixture in the process of testing,the heat treatment process is determined.Laser cladding coating bond strength experiment is carried to explore the orders of magnitude of the bond strength of laser cladding coating,concluded that the influence mechanism of the bonding state of laser cladding coating by the micro and macro mechanical properties.更多还原