Insights into nano-ZrO2 reinforced self-antibacterial Ti-3Cu composites via laser metal deposition: content-optimized bioactive nano-ZrO2 integrated for wear resistance, in vitro antibacterial and biological properties.

Ti alloys are sensitive to fretting wear, which leads to early failure of their implants. Wear is a major factor in determining the long-term clinical performance. This work explored the increase of wear resistance in antibacterial Ti-Cu alloys, by incorporating biocompatible nano-ZrO2 using laser metal deposition (LMD). The content of the reinforcing nano-ZrO2 played a crucial role in performance. There was good densification quality for ≤3 wt%. The densification quality declined and there were macrocracks for ≥5 wt%. Both the prior β grains and the α grains initially decreased in size followed by coarsening as the ZrO2 content increased, with the minimum at 3 wt%. The yield strength increased with increasing ZrO2 content, and the elastic modulus increased from 5 wt%. The wear rate decreased initially and then increased with increasing ZrO2 contents, reaching the lowest wear rate at 3 wt%. The corrosion resistance in body fluid was a minimum between 3 and 5 wt%, with less or more leading to a decrease in corrosion resistance. In vitro antibacterial tests and MC3T3-E1 cell culture assays indicated that ZrO2 contents of up to 10 wt% achieved good antibacterial effects while maintaining good biocompatibility. The comprehensive test results allowed screening and optimization of the processability and wear-related performance. 3 wt% ZrO2 contents provided the best overall performance. The mechanisms for various content bioactive nano-ZrO2 integrated for wear resistance, in vitro antibacterial and biological properties were explored. This work aimed to understand how ZrO2 concentrations influenced the overall performance and to identify the optimal content for wear resistance and related biofunctionality.