Tribological properties and mechanism of micro-arc oxidation films on the surface of TC4 oil well tubes

With the increasing development of high-inclination wells in the Zhidan Oilfield, improved oil tubing performance is of paramount importance. In this study, we address the limited friction and wear resistance of TC4 alloy tubing by employing a micro-arc oxidation (MAO) surface treatment to produce an oxide ceramic coating. The tribological performance of the MAO-treated TC4 was systematically evaluated under varying normal loads, revealing that both the friction coefficient and wear volume increase with increasing load. Compared to TC4 alloy, the MAO-treated alloy exhibited significantly improved wear resistance. When tested against TC4 counterpart balls, the dominant wear mechanisms were identified as adhesive and abrasive wear. In contrast, pairing with GCr15 steel balls additionally introduced fatigue wear. Furthermore, the cutting-to-plasticity ratio (fcp) decreased from 0.9 for untreated TC4 to 0.8 for MAO-TC4, indicating a reduction in micro-cutting and a relative enhancement in micro-ploughing, which resulted in narrower and shallower wear scratches. These results demonstrate that MAO treatment markedly improves the friction and wear resistance of titanium alloy tubing, thereby meeting the rigorous operational requirements of high-inclination wells in the Zhidan Oilfield. This strategy provides a promising and innovative approach for enhancing the surface performance of titanium alloy well pipes under demanding service conditions.