Friction and Wear Characteristics of Micro-Arc Oxidation Coating on Ti6Al4V Alloy—A Review

Ti6Al4V alloy is widely used in artificial joints, artificial bones, and dental implants due to its elastic modulus similar to that of bone, good biocompatibility and non-cytotoxicity, low density, and excellent fatigue resistance. However, its utility is constrained by the low surface hardness and inadequate wear resistance. Micro-arc oxidation (MAO) technology emerges as a surface modification method characterised by a straightforward process and superior processing efficacy, making it particularly favoured in enhancing the wear resistance of Ti6Al4V. This paper commenced by elucidating the fundamental principles of micro-arc oxidation. Subsequently, it examined the impacts of crucial parameters such as electrolyte type, concentration, processing voltage, current, time, and electrolyte additives on the friction and wear properties of Ti6Al4V alloy MAO coatings, proposing three mechanisms for optimising wear resistance. The primary strategies for augmenting the microhardness and wear resistance of Ti6Al4V alloy MAO coatings involved pore reduction even sealing, lubrication enhancement, and hard compound generation. Following this, the article synthesised the friction and wear attributes of MAO coatings in conjunction with diverse modification techniques, alongside a review of fretting wear characteristics of Ti6Al4V alloy MAO coatings. Lastly, conclusions and prospects were presented to furnish a foundation for future exploration into the wear resistance of Ti6Al4V alloy MAO coatings in scholarly endeavours.