Preparation and Properties of Micro-Arc Oxidation Coatings on Friction-Stir-Processed ZK60 Mg Alloys with Hydroxyapatite Particles

To address the challenges of excessively fast degradation and relatively poor biocompatibility of biomedical magnesium alloys, in this study, Mg/HA magnesium alloy treated by different friction stir processing (FSP) techniques served as the substrate for fabricating a micro-arc oxidation (MAO) coating. SEM, EDS, XRD, and XPS were employed to characterize the coating’s microstructure, phase composition, and element distribution, while its comprehensive properties were evaluated via electrochemical tests, nanoindentation, friction–wear experiments, contact angle measurements, and antibacterial assays. Results indicate that MAO coatings on all substrates exhibit a dense, uniform grayish-white macroscopic morphology with 3–5 μm pores. Cross-sectional observations reveal a metallurgical bond between the coating and substrate, with minor blind pores and microcracks distributed in the coating, and different coatings show similar thickness and high density. The coatings mainly consist of Ca3(PO4)2, CaCO3, Mg, MgSiO3, and MgO. HA powder is uniformly dispersed in the substrate treated by 1500-3 FSP passes, promoting more Ca2+ and PO43− release during the MAO process. This yields the highest Ca/P ratio, endowing the coating with excellent biological performance to induce osteocyte growth. All coatings have good wear/corrosion resistance and a maximum adhesion of 14.485 N. Notably, MAO coatings on substrates with 1500-3 and 1700-3 FSP passes are moderately hydrophilic, facilitating cell adhesion/spreading and meeting biomedical implants’ short-term antibacterial rate requirements.