Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

IF 1.1 Q4 ELECTROCHEMISTRY Surface Engineering and Applied Electrochemistry Pub Date : 2023-07-05 DOI:10.3103/S1068375523030134

E. V. Likrizon, S. A. Silkin, A. I. Dikusar

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引用次数: 1

Abstract—

Experimental study of the anodic dissolution of titanium and its alloys over a wide range of current densities, including pulsed currents (up to 100 A/cm²), under controlled hydrodynamic conditions and surface temperature in nitrate and chloride solutions, showed that the process is mediated by electrochemical formation of an anodic oxide film (AOF), which undergoes chemical dissolution. The AOF has a bilayer structure (two barrier films: at the interface with the metal and solution). It is described by PDM-III (Point Defect Model). Under certain conditions, it is possible to achieve a steady state in which the film growth rate is compensated by the rate of its chemical dissolution (during a pulsed treatment). In this case, there is a 100% current efficiency in terms of titanium ionization in the oxidation state of four. Under the conditions of the described experiments, i.e., when using direct current, the rate of the AOF electrochemical formation exceeds that of its chemical dissolution, which leads to a decrease in the current efficiency, which does not exceed 75%. Due to the temperature dependence of the electrical resistance of the barrier film at the interface with the solution, which determines its thickness, the current efficiency increases with an increase in the flow rate of the electrolyte. When the thermokinetic instability (TKI) of the AOF is reached (thermal explosion caused by positive feedback: the rate of electrochemical reaction–surface temperature–the rate of electrochemical reaction), the interaction of electrolyte components with the surface free from the film leads to “anomalous” anodic dissolution of the AOF with a current efficiency exceeding 100%. Regardless of the nature of the electrolyte, the TKI conditions are reached at ~1 A/cm². It has been shown that the dissolution rate in nitrate solutions for certain pulsed treatment parameters (relative pulse duration of 2, dc = 50%) (and the displacement of cathode tool in electrochemical machining) may exceed the machining rate with direct current of the same density by more than a factor of two.

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被动氧化膜结构和表面温度对电化学加工电解液中铬镍和钛合金阳极溶解速率的影响：第 2 部分。钛合金在硝酸盐和氯化物溶液中的阳极溶解

摘要--在广泛的电流密度范围内，包括脉冲电流（高达 100 A/cm2），在硝酸盐和氯化物溶液中，在受控的流体动力学条件和表面温度下，对钛及其合金阳极溶解的实验研究表明，该过程是由阳极氧化膜（AOF）的电化学形成介导的，该氧化膜会发生化学溶解。阳极氧化膜具有双层结构（在与金属和溶液的界面上有两层阻挡膜）。它由 PDM-III（点缺陷模型）描述。在某些条件下，有可能达到一种稳定状态，在这种状态下，薄膜的生长速度会得到其化学溶解速度的补偿（在脉冲处理过程中）。在这种情况下，氧化态为 4 的钛电离电流效率为 100%。在所述实验条件下，即使用直流电时，AOF 的电化学形成速度超过其化学溶解速度，导致电流效率下降，不超过 75%。由于阻挡膜与溶液界面处的电阻与温度有关，而温度又决定了阻挡膜的厚度，因此电流效率会随着电解液流速的增加而提高。当达到 AOF 的热动力学不稳定性 (TKI)（由正反馈引起的热爆炸：电化学反应速率-表面温度-电化学反应速率）时，电解质成分与脱离薄膜的表面相互作用，导致 AOF 的 "反常 "阳极溶解，电流效率超过 100%。无论电解质的性质如何，在 ~1 A/cm2 时都能达到 TKI 条件。研究表明，在某些脉冲处理参数下（相对脉冲持续时间为 2，直流 = 50%）（以及电化学加工中阴极工具的位移），硝酸盐溶液中的溶解速率可能会超过相同密度直流电加工速率的 2 倍以上。

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来源期刊

Surface Engineering and Applied Electrochemistry Engineering-Industrial and Manufacturing Engineering

CiteScore

1.70

自引率

22.20%

发文量

审稿时长

6 months

期刊介绍： Surface Engineering and Applied Electrochemistry is a journal that publishes original and review articles on theory and applications of electroerosion and electrochemical methods for the treatment of materials; physical and chemical methods for the preparation of macro-, micro-, and nanomaterials and their properties; electrical processes in engineering, chemistry, and methods for the processing of biological products and food; and application electromagnetic fields in biological systems.