模具表面激光毛化形貌成形机理及工艺实验研究

发布时间：2018-11-07 14:57

【摘要】：金属的表面处理技术作为一种融合了多个行业和多个学科的技术门类,其涉及到的内容较广,工艺方法较多,知识涵盖面较宽。常见的金属表面处理技术包括:表面改性技术,表面镀层技术,热喷涂技术,气相沉积技术以及高能束表面处理等。而激光毛化技术作为一种新型的表面处理微加工技术,通过对金属材料表面的改形改性,从而对材料表面的摩擦磨损现象起到良好的改善作用。基于激光毛化加工的这种良好效果,展开与激光毛化技术相关的基础理论与实验研究,将其应用到不同种类、不同需求的工作表面上,具有十分重要的意义。围绕激光毛化形貌的成形机理和工艺实验研究,国内外研究学者做了大量的工作,从机理解释、模拟仿真再到实验研究,均获得一系列研究成果,通过实验所获得的毛化形貌种类丰富多样,但是,针对毛化技术领域的研究仍然存在诸多问题。本文主要针对毛化形貌类型的判定标准和表征方法、如何实现毛化形貌的工艺可控性等关键问题,通过理论分析和工艺实验相结合的方法,对毛化形貌的成形机理进行阐述,建立一种表征和判定毛化点的方法,并通过特种工艺方法来尽可能地实现毛化点形貌与大小的可控性。综上所述,本文主要的研究工作如下。一、根据激光和物质相互作用的机理,对毛化形貌的成形过程进行了详细的分析、阐释,包括毛化形貌形成的物理过程变化、熔池的形成过程分析、气化现象对熔池的影响,以及熔池内部的热传导过程和温度场的分析等。二、利用SPI型光纤激光加工设备,采用单因素分析法,通过控制不同工艺参量在C r12mov模具钢试样上进行了系统的激光毛化工艺实验,对不同实验参数下加工出的毛化形貌进行检测,进行对比分析,总结了不同实验参数下毛化形貌的演变规律;并根据实验中所获得的毛化点的外形特征,建立了一种毛化点几何尺寸的表征方法和形貌种类的判定标准;研究了不同激光功率、脉冲宽度、离焦量对毛化形貌几何大小的影响规律,并对形貌形成的过程进行了分析。三、为尽可能改善毛化形貌,获得较好的毛化点质量,进而实现可控性要求,采用辅助气体、表面涂层以及水环境等不同的特种工艺方法,来探究对毛化点的影响规律。结果发现采用辅助气体为氮气时,在合适的气体压力下,所得到的毛化形貌更加均匀、规整;当表面涂层采用黑漆涂料时,毛化形貌的规律性更强,更易实现可控性。四、利用金相显微镜对毛化形貌区域的金相组织和显微硬度进行了检测,并与基体材料进行对比分析。结果发现,毛化区域材料的金相组织形态全部为马氏体组织,更加致密,毛化点位置的显微硬度整体上比基体要高出30%~45%。
[Abstract]:Metal surface treatment technology is a kind of technology that combines many industries and disciplines, which involves a wide range of contents, many process methods and wide knowledge coverage. The common metal surface treatment technologies include surface modification technology, surface coating technology, thermal spraying technology, vapor deposition technology and high energy beam surface treatment. As a new kind of surface treatment micro-processing technology, laser texturing technology can improve the friction and wear phenomenon of the metal surface by modifying the metal surface. Based on the good effect of laser texturing, it is of great significance to develop the basic theory and experimental research related to laser texturing, and to apply it to different kinds of working surfaces with different demands. A great deal of research work has been done by domestic and foreign scholars on the forming mechanism and process experiment of laser texturing. A series of research results have been obtained from mechanism interpretation, simulation and simulation to experimental research. There are many kinds of textures obtained by experiments, but there are still many problems in the field of wool technology. In this paper, aiming at the key problems, such as judging standard and characterization method of texturing morphology, how to realize the process controllability of woolening morphology, the forming mechanism of texturing morphology is expounded by combining theoretical analysis with process experiment. A method of characterizing and judging the wool point is established, and the shape and size of the wool point can be controlled as much as possible by the special process method. To sum up, the main research work of this paper is as follows. First, according to the mechanism of the interaction between laser and matter, the forming process of the Mao morphology is analyzed in detail, including the changes of the physical process of the formation of the morphology, the analysis of the forming process of the molten pool, and the influence of the gasification phenomenon on the molten pool. And the analysis of the heat conduction process and temperature field in the molten pool. Secondly, by using SPI type fiber laser processing equipment and single factor analysis method, a systematic laser wool processing experiment was carried out on C r12mov die steel sample by controlling different process parameters. The morphologies of the textures processed under different experimental parameters were examined and compared and analyzed. The evolution of the textures was summarized under different experimental parameters. According to the shape characteristics of the wool points obtained in the experiment, a method for characterizing the geometric size of the wool points and a standard for judging the morphology of the points are established. The effects of laser power, pulse width and defocus on the geometric size of the textured morphology were studied, and the formation process of the morphology was analyzed. Third, in order to improve the morphology of the wool as much as possible, obtain better quality of the wool point and realize the controllability requirement, different special process methods, such as auxiliary gas, surface coating and water environment, are adopted to explore the law of influence on the wool point. The results show that when the auxiliary gas is used as nitrogen, the morphology of the wool is more uniform and regular under the suitable gas pressure, and when the surface coating is used the black paint, the regularity of the morphology of the wool is stronger and the controllability is easier to be realized. 4. Metallographic microstructure and microhardness of the textured area were examined by metallographic microscope, and compared with the matrix material. The results show that the microstructure of the textured materials is all martensite and denser. The microhardness at the position of the wool point is 30% higher than that of the matrix as a whole.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG76;TG665

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