In this study, Co, Cr, and Ni were selected as the equal-atomic medium entropy alloy (MEA) systems, and Si was added to form CoCrNiSi0.3 MEA. In order to further improve its wear and corrosion properties, CrN film was sputtered on the surface. In addition, to enhance the adhesion between the soft CoCrNiSi0.3 substrate and the super-hard CrN film, a Cr buffer layer was pre-sputtered on the CoCrNiSi0.3 substrate. The experimental results show that the CrN film exhibits a columnar grain structure, and the film growth rate is about 2.022 μm/h. With the increase of sputtering time, the increase in CrN film thickness, and the refinement of columnar grains, the wear and corrosion resistance improves. Among all CoCrNiSi0.3 MEAs without and with CrN films prepared in this study, the CoCrNiSi0.3 MEA with 3 h-sputtered CrN film has the lowest wear rate of 2.249 × 10−5 mm3·m−1·N−1, and the best corrosion resistance of Icorr 19.37 μA·cm–2 and Rp 705.85 Ω·cm2.

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Polycrystalline HfZrO2 (HZO) film can be fabricated on as-extruded Mg–Ca alloy, which is identified by the results of XRD and TEM. HZO film can improve the corrosion resistance of as-extruded Mg–Ca alloy to further result in a decrease in the corrosion rate of Mg–Ca alloy. Corrosion current density, pH value evaluation, and the corrosion surface image provide evidence of improvement in corrosion rate. Compared with ZrO2 film, HZO film shows better short-term corrosion resistance. The results of WST-1 assay and LDH assay show that HZO film has low toxicity and is suitable for the protective coating of biological implants.