叶轮材料激光热丝熔覆工艺优化与质量评价研究

发布时间：2018-05-23 06:28

本文选题：激光热丝熔覆 + 工艺优化设计　；参考：《北京交通大学》2017年硕士论文

【摘要】：低碳马氏体析出硬化不锈钢FV520B具有良好的力学性能,被广泛用于大型离心式压缩机转子叶轮等承载零部件的制造过程。由于叶轮的工作环境苛刻,容易产生疲劳、磨损、裂纹等失效。对表面受损失效的部件进行修复再制造,不仅可以减少自然资源消耗,降低成本,更是对延长叶轮服役寿命,保障设备运转起到重要支撑作用。激光热丝熔覆相比于传统的修复技术具有热输入小、材料/能量利用率高等特点,是一种高效的修复工艺。修复后在基体组织与熔覆层形成新的界面,定量衡量其成形质量与评价修复后界面力学性能,对于保证修复质量、提供产品可靠性具有重要意义。本文针对激光热丝熔覆FV520B材料的工艺评价与界面性能评估问题,首先,提出体积缺陷率作为评价熔覆层成形质量的判据,采用田口方法设计并分析了FV520B钢激光熔覆工艺实验;通过平均信噪比分析,确定了四项关键工艺参数(激光功率、扫描速度、送丝速度、热丝电流)的最优组合,并采用方差分析明确了各参数对熔覆层成形质量的贡献率。结果表明,在最优的工艺参数下,界面结合良好,金相组织均匀,无杂质气孔,说明熔覆过程平稳连续,具有良好的成形质量。其次,通过响应曲面法分析了单因子和多因子交互作用的影响规律,建立了反映单道次熔覆工艺参数和成形质量关系的回归模型和经验公式。同时,在获得稳定热丝过渡的前提下,设计了多点测温试验,得到激光熔覆过程温度场的三维空间分布,通过建立熔覆过程温度场分布模型,分析了温度、组织和性能之间的映射关系。最后,结合工艺参数与成形质量之间的拟合方程,建立搭接率模型,量化分析激光热丝多道次熔覆过程。在激光热丝熔覆工艺参数优化的基础上,设计了高强钢熔覆界面结合强度的测量方法与实验装置,定量表征熔覆层基体界面结合强度。结果表明,在激光功率P为1910 W、扫描速度Vs为6.5 mm/s、送丝速度Vf为2.5 m/min、熔覆电流I为50 A、搭接率n为43.13%时,可以形成大面积组织均匀致密的多道次修复层。此时熔覆层基体间界面结合强度为1026.6 MPa,与基体材料强度基本相同,达到了较好的熔覆修复效果。
[Abstract]:Low-carbon martensite precipitation hardening stainless steel (FV520B) has good mechanical properties and is widely used in the manufacturing process of bearing parts such as rotor impeller of large centrifugal compressor. Due to the harsh working environment of the impeller, fatigue, wear, crack and other failures are easy to occur. The repair and remanufacture of damaged parts can not only reduce the consumption of natural resources and reduce the cost, but also prolong the service life of impeller and support the operation of equipment. Compared with the traditional repair technology, laser hot wire cladding has the advantages of small heat input and high material / energy utilization ratio, so it is an efficient repair process. A new interface was formed between the matrix structure and the cladding layer after repair. It is of great significance to quantitatively evaluate the forming quality and evaluate the mechanical properties of the interface in order to guarantee the repair quality and provide the product reliability. In this paper, the process evaluation and interface performance evaluation of laser hot-wire cladding FV520B material are discussed. Firstly, the volumetric defect rate is proposed as the criterion to evaluate the forming quality of the cladding layer. Taguchi method is used to design and analyze the laser cladding process experiment of FV520B steel. The optimal combination of four key process parameters (laser power, scanning speed, wire feeding speed, hot wire current) was determined by the analysis of average SNR, and the contribution rate of each parameter to the forming quality of the cladding layer was determined by variance analysis. The results show that under the optimum process parameters, the interface is well bonded, the metallographic structure is uniform, and there is no impurity porosity, which indicates that the cladding process is stable and continuous, and has good forming quality. Secondly, the law of interaction between single factor and multi-factor is analyzed by response surface method, and the regression model and empirical formula are established to reflect the relationship between process parameters and forming quality of single pass cladding. At the same time, on the premise of obtaining stable hot wire transition, a multi-point temperature measurement test is designed to obtain the three-dimensional spatial distribution of the temperature field in the laser cladding process. The temperature distribution model is established and the temperature is analyzed. Mapping between organization and performance. Finally, based on the fitting equation between process parameters and forming quality, the overlap rate model is established, and the multipass cladding process of laser hot wire is analyzed quantitatively. Based on the optimization of laser hot wire cladding process parameters, the measuring method and experimental device for the interface bonding strength of high strength steel cladding were designed, and the interface bonding strength of the cladding substrate was quantitatively characterized. The results show that when the laser power P is 1910 W, the scanning speed Vs is 6.5 mm / s, the wire feeding speed V f is 2.5 m / min, the cladding current I is 50 A, and the lap ratio n is 43.13, the multipass repair layer with uniform and compact structure can be formed. The interfacial bonding strength of the cladding layer is 1026.6 MPA, which is basically the same as that of the substrate material, and the effect of cladding repair is good.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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