TC4钛合金表面熔盐电解渗硼工艺及性能的研究
发布时间：2018-07-29 07:26
【摘要】：为了提高TC4钛合金的硬度,利用熔盐电解法,采用FCl NaK-Na2B4O7熔盐体系,于TC4钛合金(Ti6Al4V)基体上制备渗硼层。选用NaCl-KCl-NaF-Na2B4O7摩尔比为2:2:1:0.04的熔盐于试样表面进行熔盐电解渗硼,运用增重法、辉光放电光谱仪、扫描电子显微镜及X射线衍射分析仪等分析手段,分析研究了电流密度、占空比、电解时间和电解温度等工艺参数的变化对渗硼层沉积速率、厚度、成分、形貌和物相组成的影响,利用显微硬度计和电化学工作站测量了基体和渗硼试样的硬度和耐腐蚀性,同时从热力学和动力学角度对渗硼过程进行了探究。研究结果表明:电解时间增长,电解温度增高,渗硼层的沉积速率增大,同时所制备的渗硼层的厚度增高;当电流密度由小到大变化时,渗硼层的沉积速率和所制备渗硼层的厚度都呈现先增大后减小的趋势,且沉积速率和渗层厚度都在电流密度60m A/cm2时达到峰值;伴随着占空比上升,沉积速率降低,但不同占空比下所得渗层的厚度相差不大。渗硼层不含Al,而V则易固溶于硼化物中。伴随着电解时间的延长,电解温度的升高以及占空比的变大,渗硼层表面晶粒由细小变得粗大;当电流密度升高,渗硼层晶粒变小;电解时间较短(30min)基体表面没有形成合金层。渗硼层主要由TiB和TiB2组成,渗硼层在(111)晶面上择优生长;因较小原子半径的V元素固溶于较大原子半径的Ti中造成渗硼层的Ti B相的衍射峰向大角度偏移。采用熔盐电解法于TC4钛合金表面进行渗硼的最优工艺参数为:电流密度60mA/cm2,占空比20%,电解时间90min,电解温度840℃,电解周期1000μs。经渗硼处理后基体硬度和耐腐蚀性均得到改善。渗硼过程存在的反应中,Ti+2B=TiB2优先进行;随着温度升高,硼在TC4钛合金里拥有更大的扩散系数,扩散激活能约为68.1KJ/mol。
[Abstract]:In order to improve the hardness of TC4 titanium alloy, boronizing layer was prepared on the substrate of TC4 titanium alloy (Ti6Al4V) by molten salt electrolysis and FCl NaK-Na2B4O7 molten salt system. The molten salt with NaCl-KCl-NaF-Na2B4O7 molar ratio of 2: 1: 0.04 was selected to carry out electrolytic boronizing on the surface of the sample. The current density and duty cycle were studied by means of weight gain method, glow discharge spectrometer, scanning electron microscope and X-ray diffraction analyzer. The effects of electrolysis time and electrolysis temperature on the deposition rate, thickness, composition, morphology and phase composition of boronized layer were studied. The hardness and corrosion resistance of the matrix and boronized samples were measured by microhardness meter and electrochemical workstation. At the same time, the boronizing process was studied from the point of view of thermodynamics and kinetics. The results show that the deposition rate of boronized layer and the thickness of boronized layer increase with the increase of electrolysis time and temperature, and when the current density changes from small to large, The deposition rate and thickness of boronized layer increased first and then decreased, and the deposition rate and thickness of boronized layer reached the peak value at 60 m A/cm2 of current density, and the deposition rate decreased with the increase of duty cycle. However, the thickness of the permeable layer under different duty cycle has little difference. Boronized layer does not contain Al, while V is easily solid solution in boride. With the increase of electrolysis time, the increase of electrolysis temperature and duty cycle, the grain size of boronized layer changes from fine to coarse; when the current density increases, the grain size of boronized layer becomes smaller; the electrolysis time is shorter (30min) substrate surface does not form alloy layer. The boronizing layer is mainly composed of TiB and TiB2, and the boronized layer grows preferentially on the (111) crystal plane, and the diffraction peak of the B phase of the boronized layer is shifted to a large angle due to the solid solution of V element with a smaller atomic radius in Ti with a larger atomic radius. The optimum technological parameters of boronizing on the surface of TC4 titanium alloy by molten salt electrolysis are as follows: current density 60 Ma / cm 2, duty cycle 20, electrolysis time 90 min, electrolysis temperature 840 鈩，
本文编号：2151949
[Abstract]:In order to improve the hardness of TC4 titanium alloy, boronizing layer was prepared on the substrate of TC4 titanium alloy (Ti6Al4V) by molten salt electrolysis and FCl NaK-Na2B4O7 molten salt system. The molten salt with NaCl-KCl-NaF-Na2B4O7 molar ratio of 2: 1: 0.04 was selected to carry out electrolytic boronizing on the surface of the sample. The current density and duty cycle were studied by means of weight gain method, glow discharge spectrometer, scanning electron microscope and X-ray diffraction analyzer. The effects of electrolysis time and electrolysis temperature on the deposition rate, thickness, composition, morphology and phase composition of boronized layer were studied. The hardness and corrosion resistance of the matrix and boronized samples were measured by microhardness meter and electrochemical workstation. At the same time, the boronizing process was studied from the point of view of thermodynamics and kinetics. The results show that the deposition rate of boronized layer and the thickness of boronized layer increase with the increase of electrolysis time and temperature, and when the current density changes from small to large, The deposition rate and thickness of boronized layer increased first and then decreased, and the deposition rate and thickness of boronized layer reached the peak value at 60 m A/cm2 of current density, and the deposition rate decreased with the increase of duty cycle. However, the thickness of the permeable layer under different duty cycle has little difference. Boronized layer does not contain Al, while V is easily solid solution in boride. With the increase of electrolysis time, the increase of electrolysis temperature and duty cycle, the grain size of boronized layer changes from fine to coarse; when the current density increases, the grain size of boronized layer becomes smaller; the electrolysis time is shorter (30min) substrate surface does not form alloy layer. The boronizing layer is mainly composed of TiB and TiB2, and the boronized layer grows preferentially on the (111) crystal plane, and the diffraction peak of the B phase of the boronized layer is shifted to a large angle due to the solid solution of V element with a smaller atomic radius in Ti with a larger atomic radius. The optimum technological parameters of boronizing on the surface of TC4 titanium alloy by molten salt electrolysis are as follows: current density 60 Ma / cm 2, duty cycle 20, electrolysis time 90 min, electrolysis temperature 840 鈩，
本文编号：2151949
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