基于卤素效应的阳极氧化技术提高Ti48Al5Nb合金抗高温氧化性能

Enhancement of High Temperature Oxidation Resistance of Ti48Al5Nb Alloy via Anodic Anodization in NH_4F Containing Ethylene Glycol

采用电化学阳极氧化技术在含NH_4F的乙二醇电解液中对Ti48Al5Nb合金进行阳极氧化处理,以获得富铝含氟阳极氧化膜。研究了阳极氧化处理对Ti48Al5Nb合金在1000℃空气中的氧化行为及氧化膜组成和结构的影响。结果表明:阳极氧化处理的Ti48Al5Nb合金经高温氧化后表面可形成连续、致密的Al_2O_3氧化膜,且氧化膜与基体具有良好结合力,有效阻止了氧向内扩散,进而显著提高了合金的抗高温氧化性能。经1000℃氧化100 h后,阳极氧化试样增重由未经阳极氧化处理试样的26.73 mg/cm^2降至1.18 mg/cm^2。同时,阳极氧化处理改变了合金的氧化机制,抑制了氧化膜/基体界面处富Nb层的出现。阳极氧化提高Ti48Al5Nb合金抗高温氧化性能是由于氧化膜中F在高温氧化过程中表现出的"卤素效应"所致。

Ti48Al5Nb alloy was electrochemically anodized in electrolyte of ethylene glycol with NH4F to prepare anodic films containing fluorine and aluminum.The influence of anodization treatment on the oxidation behavior,the composition and structure of the oxide scale of the anodized Ti48Al5Nb alloy were then characterized.Results shown that a continuous and dense Al2O3 oxide scale will generate on the anodized Ti48Al5Nb alloy after high temperature oxidation.And this oxide scale has good adhesion with the substrate,therefore can efficiently prevent the inward diffusion of oxygen,resulting the enhanced high temperature oxidation resistance.After oxidation at 1000℃for 100 h,the weight gain of the anodized Ti48Al5Nb alloy was dramatically decreased from 26.73 mg·cm-2 for the bare Ti48Al5Nb alloy to 1.18 mg·cm-2.Moreover,it is shown that anodization also changes the oxidation mechanism,leading to the disappearance of the Nb-enriched layer at the interface between the oxide scale and substrate.The enhanced high temperature oxidation of the anodized Ti48Al5Nb is derived from the halogen effect based on the fluorine compounds existed in the anodized film.