微弧氧化对TC4钛螺栓/45钢连接腐蚀行为的影响

Effect of Micro Arc Oxidation on the Corrosion Behavior of TC4 Titanium Bolt/45 Steel Connection

为了解决TC4钛螺栓/45钢偶对因电位差而引发的连接腐蚀问题,在恒流模式下,分别用单极性脉冲和双极性脉冲在TC4钛螺栓表面制备出致密程度不同的陶瓷层,对比研究了微弧氧化对TC4钛螺栓与45钢连接腐蚀行为的影响。通过涡流测厚仪、SEM、XRD和电化学阻抗测试表征了陶瓷层的厚度、微结构、相组成和阻抗值,采用盐雾试验研究了不同连接偶中45钢的腐蚀程度。结果表明:双极性脉冲模式提高了陶瓷层的致密性和绝缘强度,双极性脉冲陶瓷层的阻抗值比单极性脉冲陶瓷层提高了4.15倍,比TC4基体试样提高了19.78倍,而其相组成与单极性脉冲陶瓷层相比未发生改变。微弧氧化处理延长了钛螺栓/45钢连接偶的连接腐蚀寿命,经盐雾腐蚀1 000 h后,与双极性脉冲钛螺栓偶合的45钢表面几乎无腐蚀痕迹,抗连接腐蚀性能最佳。

In order to solve the problem of connection corrosion caused by potential difference between TC4 titanium bolt and 45 steel couple, ceramic coatings with different compactness were prepared on the surface of TC4 titanium bolt using unipolar pulse and bipolar pulse respectively in constant current mode, and the effect of micro arc oxidation on the corrosion behavior of the connection between TC4 titanium bolt and 45 steel was studied. Moreover, the thickness, microstructure, phase composition and impedance of ceramic coatings were characterized by eddy current thickness gauge, SEM, XRD and electrochemical impedance test. The corrosion degrees of 45 steel in different coupling pairs were studied by salt spray test. Results showed that the bipolar pulse mode improved the compactness and dielectric strength of the ceramic coating, the impedance value of bipolar pulse ceramic coating was 4.15 times higher than that of the unipolar pulse ceramic coating, and 19.78 times higher than that of the untreated TC4 substrate. Meanwhile, the phase composition of bipolar pulse ceramic coating was the same as that of the unipolar pulse ceramic coating. Micro arc oxidation treatment prolonged the corrosion life of titanium bolt/45 steel coupling pair, and after 1 000 h of salt spray corrosion, the surface of 45 steel coupled with bipolar pulse titanium bolt had almost no corrosion trace, indicating that the corrosion resistance of the connection was the best.