文摘
Titanium alloys are widely used in the aerospace and biomedical industries. Micro-dimple arrays, as a kind of surface texture, have been applied on titanium alloy surfaces to enhance tribological behaviour as well as to affect the biological performance of titanium implants. Through-mask electrochemical micromachining (TMEMM) is a promising approach to generate micro-dimple arrays on metal surfaces. In general, sodium bromide and methanol–sulfuric acid, which could dissolve the passive oxide layer on titanium alloy surfaces, are used as electrolytes to generate micro-dimple arrays. However, these electrolytes are caustic, which can damage the equipment, and are unfavourable for industrial applications. In this paper, an environmentally friendly NaNO3 electrolyte was employed to generate micro-dimple arrays on titanium alloy surfaces in TMEMM with a reusable mask; this made the process more efficient and safer. Experiments showed that there was serious stray corrosion on the titanium alloy surfaces when the micro-dimple arrays were generated using direct current. To obtain high-quality micro-dimple arrays, a pulsed current was employed in TMEMM. The results showed that machining parameters of applied voltage of 24 V, pulse duty cycle of 10 % and frequency of 100 Hz were appropriate to improve the machining quality. Micro-dimple arrays with no stray corrosion were thus generated. Moreover, the electrolyte temperature also influenced the machining accuracy, and a low electrolyte temperature of 20 °C was useful to reduce the undercutting of micro-dimples and improve machining localization. With the optimized parameters, micro-dimples with a diameter of 110 μm and depth of 20 μm were generated.
