【摘要】：為了提高TC4鈦合金的硬度,利用熔鹽電解法,采用FCl NaK-Na2B4O7熔鹽體系,于TC4鈦合金(Ti6Al4V)基體上制備滲硼層。選用NaCl-KCl-NaF-Na2B4O7摩爾比為2:2:1:0.04的熔鹽于試樣表面進(jìn)行熔鹽電解滲硼,運(yùn)用增重法、輝光放電光譜儀、掃描電子顯微鏡及X射線衍射分析儀等分析手段,分析研究了電流密度、占空比、電解時(shí)間和電解溫度等工藝參數(shù)的變化對(duì)滲硼層沉積速率、厚度、成分、形貌和物相組成的影響,利用顯微硬度計(jì)和電化學(xué)工作站測(cè)量了基體和滲硼試樣的硬度和耐腐蝕性,同時(shí)從熱力學(xué)和動(dòng)力學(xué)角度對(duì)滲硼過(guò)程進(jìn)行了探究。研究結(jié)果表明:電解時(shí)間增長(zhǎng),電解溫度增高,滲硼層的沉積速率增大,同時(shí)所制備的滲硼層的厚度增高;當(dāng)電流密度由小到大變化時(shí),滲硼層的沉積速率和所制備滲硼層的厚度都呈現(xiàn)先增大后減小的趨勢(shì),且沉積速率和滲層厚度都在電流密度60m A/cm2時(shí)達(dá)到峰值;伴隨著占空比上升,沉積速率降低,但不同占空比下所得滲層的厚度相差不大。滲硼層不含Al,而V則易固溶于硼化物中。伴隨著電解時(shí)間的延長(zhǎng),電解溫度的升高以及占空比的變大,滲硼層表面晶粒由細(xì)小變得粗大;當(dāng)電流密度升高,滲硼層晶粒變小;電解時(shí)間較短(30min)基體表面沒(méi)有形成合金層。滲硼層主要由TiB和TiB2組成,滲硼層在(111)晶面上擇優(yōu)生長(zhǎng);因較小原子半徑的V元素固溶于較大原子半徑的Ti中造成滲硼層的Ti B相的衍射峰向大角度偏移。采用熔鹽電解法于TC4鈦合金表面進(jìn)行滲硼的最優(yōu)工藝參數(shù)為:電流密度60mA/cm2,占空比20%,電解時(shí)間90min,電解溫度840℃,電解周期1000μs。經(jīng)滲硼處理后基體硬度和耐腐蝕性均得到改善。滲硼過(guò)程存在的反應(yīng)中,Ti+2B=TiB2優(yōu)先進(jìn)行;隨著溫度升高,硼在TC4鈦合金里擁有更大的擴(kuò)散系數(shù),擴(kuò)散激活能約為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，

本文編號(hào)：2151949