TC4钛合金表面纳米颗粒增强的钛铝激光熔覆涂层制备及仿真研究

发布时间：2018-02-28 10:35

本文关键词： 激光熔覆 TC4钛合金纳米TiC 纳米Y_2O_3 温度场仿真显微硬度　出处：《南京航空航天大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文对在TC4钛合金表面激光熔覆制备纳米颗粒增强的钛铝复合熔覆层进行了基础研究,主要包括纳米Y_2O_3颗粒分散行为研究、激光熔覆过程仿真、TC4钛合金表面纳米颗粒增强钛铝复合熔覆层的制备,激光熔覆工艺参数的优化以及熔覆层显微组织及性能分析。本文主要开展的研究内容如下:(1)通过对纳米Y_2O_3颗粒超声分散进行单因素试验,分析了分散介质、添加粉体理论质量分数、分散时间对超声分散效果的影响,对超声工艺参数进行了优化。通过对纳米Y_2O_3粉体球磨分散进行正交试验,分析了球磨转速、球料比、球磨时间对纳米Y_2O_3球磨分散效果的影响,进行了球磨工艺参数优化;研究了纳米Y_2O_3在不同分散方式下的分散行为,得到了纳米Y_2O_3最佳分散方式为“球磨/超声”复合分散。(2)通过正交试验,对钛铝原子比1:1熔覆层制备过程中的工艺参数进行优化;基于正交试验结果,通过单因素试验对不同钛铝原子比、不同纳米TiC添加量、不同纳米Y_2O_3添加量及纳米TiC、纳米Y_2O_3双相增强钛铝复合熔覆层制备过程中的工艺参数进行进一步优化,采用激光功率700W,光斑直径1mm,扫描速度200mm·min-1,可获得表面及熔道边缘相对平整,熔道宽度一致性相对较好的熔覆层。(3)建立了TC4钛合金表面压片预置钛铝复合粉体激光熔覆过程三维瞬态温度场有限元仿真模型,研究了激光功率、扫描速度和光斑直径对熔池尺寸、熔池中心最高温度、熔池内温度梯度、温度变化率及形状控制因子的影响规律;通过单因素仿真试验,确立了相对合理的激光加工参数范围;通过正交仿真试验,比较不同激光工艺参数对温度场的影响显著性。讨论了采用激光比能综合表征激光功率、扫描速度和光斑直径的局限性。(4)对不同钛铝原子比、不同纳米TiC添加量、不同纳米Y_2O_3添加量等10种成分不同的钛铝复合熔覆层,采用SEM、EDS、XRD及显微硬度计进行显微组织、成分及显微硬度研究分析。研究表明,各熔覆层中存在大量Ti3Al、TiAl、TiAl3金属间化合物及少量对应的稀土相和陶瓷相,各熔覆层显微硬度相比于钛合金基材都有不同程度的提升,其中纳米TiC作为陶瓷相可显著提高熔覆层硬度,纳米Y_2O_3作为稀土相能有效改善显微硬度分布的均匀性及分布深度范围。
[Abstract]:In this paper, the laser cladding of nano-particles reinforced titanium-aluminum composite cladding layer on the surface of TC4 titanium alloy was studied, including the dispersion behavior of nano-Y _ 2O _ I _ S _ 3 particles. Simulation of Laser cladding process preparation of Nano-particles reinforced Ti-Al Composite cladding layer on TC4 Titanium Alloy Surface, Optimization of technological parameters of laser cladding and analysis of microstructure and properties of cladding layer. The main research contents in this paper are as follows: (1) the dispersion medium is analyzed by single factor experiment on ultrasonic dispersion of nanometer YSP _ 2O _ 3 particles. The effects of theoretical mass fraction of powder and dispersing time on the ultrasonic dispersion effect were optimized, and the ultrasonic process parameters were optimized. By orthogonal test on the dispersion of Y _ 2O _ 3 nano-powder, the rotational speed of ball mill and the ratio of ball to material were analyzed. The effect of ball milling time on the dispersion effect of nanometer Ys _ 2O _ 3 ball mill was optimized, and the dispersion behavior of Y _ 2O _ 3 nano-sized Ys _ 2O _ 3 in different dispersion modes was studied. The optimum dispersion mode of Y _ 2O _ 3 nanocrystalline Y _ 2O _ 3 is "ball mill / ultrasonic" composite dispersion. Through orthogonal experiment, the technological parameters in the preparation of titanium aluminum atomic ratio 1: 1 cladding layer are optimized, based on the results of orthogonal test, The technological parameters of Ti / Al / Al / Al / Ti / Al / Ti / Al / Ti / Al / Al / Ti / Al composite cladding coatings were further optimized by single factor experiments, including different ratios of Ti / Al atoms, different amount of nano-sized TiC, different amount of Y _ 2O _ 3 / S _ 2O _ 3 and nano-TiC, nano-Y _ 2O _ 3 and Y _ 2O _ 3, respectively. With laser power 700W, spot diameter 1mm, scanning speed 200mm 路min-1, the surface and fuse edge are relatively flat. The finite element simulation model of 3D transient temperature field during laser cladding process of TC4 titanium alloy surface preset Ti-Al composite powder was established, and the laser power was studied. The effects of scanning speed and spot diameter on the size of the molten pool, the maximum temperature of the molten pool center, the temperature gradient in the molten pool, the temperature change rate and the shape control factor are studied. The effects of different laser parameters on the temperature field were compared by orthogonal simulation experiments, and the effects of laser specific energy on different Ti / Al atom ratios were discussed, such as laser power, scanning speed and spot diameter. The microstructure, composition and microhardness of 10 kinds of titanium-aluminum composite cladding coatings with different content of nanometer TiC and different content of Ys / S _ 2O _ 3 were studied by means of SEM EDS-XRD and microhardness meter. There are a large number of Ti _ 3Al _ 2O _ TiAl _ (3) intermetallic compounds and a few corresponding rare earth phases and ceramic phases in each cladding layer. The microhardness of each cladding layer is improved in varying degrees compared with that of titanium alloy substrate, and the hardness of the cladding layer can be significantly improved by using nanometer TiC as ceramic phase. As rare earth phase, the distribution uniformity and depth range of microhardness distribution can be effectively improved by using Y _ 2O _ 3 nanoparticles as rare earth phase.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG174.4

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