CoCrMo合金激光选区熔化成型工艺与组织性能研究

发布时间：2019-06-27 07:52

【摘要】：CoCrMo合金是最常见的医用金属材料之一,其可加工能力强、性能良好,在医学领域具有广阔的应用前景。近年来,随着增材制造技术(Additive Manufacturing,AM)的发展,个性化的制造进程加快,而激光选区熔化(Selective Laser Melting,SLM)是金属增材制造领域的代表性技术,能够直接快速成型具有复杂结构、高性能、高精度的功能零件,为CoCrMo合金在医学领域的个性化直接制造提供基础。本文以符合ASTMF75标准的CoCrMo合金粉末作为实验材料,通过激光选区熔化技术直接成型,对成型工艺及成型件性能进行基础研究与分析。主要内容包括以下几个方面:(1)在成型工艺方面,对SLM成型中的关键问题进行分析研究,在此基础上对CoCrMo合金进行工艺优化,选取激光功率、扫描速度、扫描间距三个重要因素进行实验分析。通过正交试验与响应曲面分析方法对成型因素之间的交互作用进行研究,获得优化的参数组合,可以使成型致密度在98%以上。观察SLM成型CoCrMo合金的显微组织并测试相关成分,成型件在常温下主要存在一种相,显微组织致密,熔道特征明显。成型后样件的元素含量变化较小,符合ASTMF75标准要求。(2)在成型质量方面,通过优化的工艺参数成型CoCrMo合金样件,从成型样件的表面精度、尺寸精度及缺陷检测等多个方面进行研究。SLM成型CoCrMo合金的表面粗糙度约为20μm,且可以通过不同的后处理工艺进行改善。由于受成型机理的影响,实际中成型尺寸和形状会产生误差,但误差偏移率均在1%以下。通过探伤检测发现成型件表面及内部无裂纹、夹杂等缺陷,成型质量要优于铸造件。(3)在成型性能方面,对成型件的机械性能、耐腐蚀性能、残余应力等多个方面进行实验测试,全面地分析SLM成型CoCrMo合金的性能。可以得到,SLM直接成型CoCrMo合金的强度和耐腐蚀性均优于铸造件,但韧性较差,成型中存在应力分布不均的现象。在此基础上,对CoCrMo合金的相图进行分析探讨,制定合理的热处理实验方案,通过不同的热处理条件改善SLM成型CoCrMo合金的性能,保证成型件的综合性能满足ASTMF75标准要求。通过本文的研究,能够为SLM成型CoCrMo合金在医学植入体领域的应用提供依据,对CoCrMo的个性化直接制造具有重要意义。
[Abstract]:CoCrMo alloy is one of the most common medical metal materials, which has strong machinability and good properties, and has a broad application prospect in the field of medicine. In recent years, with the development of material increasing manufacturing technology (Additive Manufacturing,AM), the personalized manufacturing process is accelerated, and laser selective melting (Selective Laser Melting,SLM) is a representative technology in the field of metal material increasing manufacturing, which can directly rapid prototyping functional parts with complex structure, high performance and high precision, which provides the basis for personalized direct manufacturing of CoCrMo alloy in the field of medicine. In this paper, the CoCrMo alloy powder in accordance with ASTMF75 standard is used as the experimental material, and the forming process and the properties of the forming parts are studied and analyzed by laser selective melting technology. The main contents are as follows: (1) in the aspect of molding process, the key problems in SLM molding are analyzed and studied. on this basis, the process optimization of CoCrMo alloy is carried out, and three important factors, laser power, scanning speed and scanning spacing, are selected for experimental analysis. The interaction between molding factors is studied by orthogonal test and response surface analysis, and the optimized parameter combination is obtained, which can make the molding density more than 98%. The microstructure of CoCrMo alloy formed by SLM was observed and the related components were tested. there was a phase in the molding parts at room temperature, the microstructure was dense and the melting channel characteristics were obvious. The change of element content of CoCrMo alloy after molding is small, which meets the requirements of ASTMF75 standard. (2) in the aspect of molding quality, the surface roughness of CoCrMo alloy is about 20 渭 m, which can be improved by different post-treatment processes, and the surface accuracy, dimension accuracy and defect detection of SLM alloy are studied from the aspects of surface accuracy, dimensional accuracy and defect detection. Due to the influence of molding mechanism, the size and shape of molding will produce errors, but the error offset is less than 1%. Through flaw detection, it is found that there are no cracks and inclusions in the surface and interior of the molded parts, and the molding quality is better than that of the castings. (3) in the aspect of molding properties, the mechanical properties, corrosion resistance and residual stress of the molded parts are tested, and the properties of CoCrMo alloy formed by SLM are analyzed comprehensively. It can be obtained that the strength and corrosion resistance of CoCrMo alloy directly formed by SLM are better than those of castings, but the toughness is poor, and there is an uneven stress distribution in the molding. On this basis, the phase diagram of CoCrMo alloy is analyzed and discussed, and a reasonable heat treatment experimental scheme is worked out. The properties of CoCrMo alloy formed by SLM are improved through different heat treatment conditions, and the comprehensive properties of molding parts meet the requirements of ASTMF75 standard. Through the research in this paper, it can provide the basis for the application of SLM formed CoCrMo alloy in the field of medical implantation, and it is of great significance for the personalized direct manufacture of CoCrMo.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG665

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