Ti6Al4V钛合金渗碳层在HF中的腐蚀行为

用真空感应渗碳方法对Ti6Al4V钛合金进行高速渗碳,研究了渗碳层在HF溶液中的腐蚀行为。对腐蚀前后渗碳层的相结构和形貌的分析发现：对Ti6Al4V钛合金高速渗碳后,在表面生成一层TiC和CTi_0.42V_1.58复合化合物相的渗碳层。因为表面有渗碳层,Ti6Al4V钛合金在浓度为0.2%的HF中?泡其腐蚀速率从4.65×10^-10 g·m^-2·h^-1降低到3.3×10^-10 g·m^-2·h^-1。电化学腐蚀测试结果表明,其自腐蚀电位从未渗碳时的-0.94 V升高到-0.68 V,腐蚀电流密度从4.10 mA·cm^-2降至1.65 mA·cm^-2,极化电阻从6.36 Ω·cm²增大到15.8 Ω·cm²,R_t从0.2 Ω·cm²增大到5.7 Ω·cm²。渗碳层具有n型半导体特性,未渗碳样品具有p型半导体特性。Ti6Al4V钛合金渗碳后,在腐蚀过程中电子转移的阻力增大,使耐蚀性提高。F^-对Ti6Al4V钛合金渗碳层的腐蚀机理,主要是析氢腐蚀。

Corrosion Behavior of Carburized Ti6Al4V Ti-alloy in HF Solution

The rapid carburization of Ti6Al4V titanium alloy was carried out by vacuum induction carburizing method. The corrosion behavior of carburized Ti-alloy in HF solution was investigated. Results show that after rapid carburization a layer of TiC and CTi_0.42V_1.58 composite compound was formed on the surface of T-alloy, and in comparison with the blank Ti-alloy, the corrosion rate in 0.2% HF solution decreases from 4.65×10^-10 g·m^-2·h^-1 to 3.3×10^-10 g·m^-2·h^-1 for the carburized Ti-alloy. Correspondingly, the free-corrosion potential increased from -0.94 V to -0.68 V, the corrosion current density decreased from 4.10 mA·cm^-2 to 1.65 mA·cm^-2, the polarization resistance increases from 6.36 Ω·cm² to 15.8 Ω·cm² and R_t increases from 0.2 Ω·cm² to 5.7 Ω·cm². The corrosion product of carburized layer mainly exhibits n-type semiconductor characteristics, and that of the blank Ti-alloy exhibits p-type semiconductor characteristics. The corrosion mechanism of F^- on the carburized layer of Ti6Al4V Ti-alloy is mainly hydrogen evolution corrosion.