Preparation and performance analysis of Ti-25Nb-3Zr-2Sn-3Mo microarc oxidized macro-micro-nano tertiary structure film layers

After undergoing microarc oxidation, titanium alloys exhibit significantly enhanced biocompatibility, making them a subject of extensive research in the field of biomedical applications. In this study, a two-step microarc oxidation method was used to prepare a film layer with both macro-micro-nano tertiary structures on β-type titanium alloy Ti-3Zr-2Sn-3Mo-25Nb (TLM), using a phosphate-nitrate mixed electrolyte for the first step of microarc oxidation and a borate body electrolyte for the second step of microarc oxidation. The effects of NaOH concentration, microarc oxidation voltage, and time on the size and distribution of macropores prepared by microarc oxidation in the first step were investigated by SEM, energy dispersive spectroscopy, XRD, and metallurgical microscopy. The wettability of the prepared three-level structured film and its ability to induce hydroxyapatite deposition were evaluated through contact angle testing and simulated body fluid immersion experiments. The overall research findings indicate that the two-step microarc oxidation process yielded macropores with diameters ranging from 200 to 400 μm, along with micro-nanostructures measuring 2–15 μm and 10–100 nm. The increase in the NaOH concentration in the electrolyte decreased the size of the macropores. The increase in the microarc oxidation time increased the size of macropores; the voltage affected the distribution and number of macropores. The prepared macro-micro-nano tertiary structured membrane layers have excellent wettability and the ability to induce hydroxyapatite precipitation, indicating that they possess good biocompatibility. This study provides a reference for the medical development of alloys.