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采用熔盐电解法对TC4合金表面渗硼。用质量比为8∶2的无水硼砂-无水碳酸钠熔盐体系在1500~4500 A/m2的电流密度下进行渗硼试验,利用XRD对渗硼试样表面进行物相分析,用扫描电镜观察渗硼试样的断面形貌并用能谱(EDS)进行元素分析,研究了电流密度对渗层结构的影响,并对TC4合金的渗硼机理进行了分析。结果表明,电流密度为3500 A/m2时渗硼效果较好,渗层外层结构均匀密实,主要物相是TiB2,内层为TiB,渗层中还检测到少量V2B3。综合考虑试验结果及反应的标准吉布斯自由能计算推测出TC4合金渗硼时,在电流作用下,先在合金表面还原生成Na,然后Na将B2O3中的B置换,与合金的Ti反应生成TiB2及TiB。
Molten salt electrolysis is used to infiltrate the surface of TC4 alloy. The boronizing test was carried out at a current density of 1,500- 4,500 A / m2 with an anhydrous borax-anhydrous sodium carbonate molten salt mass ratio of 8: 2. The surface of the boronized sample was analyzed by XRD. The scanning electron microscope The cross-sectional morphology of boron-infiltrated samples was observed by electron microscope and the elemental analysis was carried out by energy dispersive spectroscopy (EDS). The effect of current density on the structure of the infiltrated layer was studied. The boronizing mechanism of TC4 alloy was also analyzed. The results show that the boronizing effect is better when the current density is 3500 A / m2, and the outer layer structure is uniform and compact. The main phase is TiB2, the inner layer is TiB, and a small amount of V2B3 is also detected in the layer. Taking into account the experimental results and the standard Gibbs free energy calculations, it is inferred that when the TC4 alloy is infiltrated, Na is reduced to the surface of the alloy under the action of electric current, then Na replaces B in the B2O3 and reacts with the Ti of the alloy TiB2 and TiB.