Cailiao Baohu (Nov 2022)
Effect of Micro Arc Oxidation on the Corrosion Behavior of TC4 Titanium Bolt/45 Steel Connection
Abstract
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.
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