The growth of anti-friction and wear-resistance TiO2 nanotube arrays driven by residual stress

Ti-based materials have attracted considerable attention for potential applications in biomedicine due to their excellent chemical inertness, biocompatibility and corrosion resistance. However, the poor friction properties of oxide films (e.g. TiO2) on Ti-based materials significantly deteriorate their service life. Here, the effect of residual stress improves the frictional properties of TiO2 nanotubes were studied. The results show that the residual stresses at the surface of the non-peened sample and the samples peened by steel balls with diameters of 4 and 6 mm are 10.17, 49.97 and 65.31 MPa, respectively. The increase in residual stress improves the growth rate of the TiO2 nanotubes. Meanwhile, with increasing residual stress, the friction coefficient and the wear rates decreases. It is noteworthy that a bridge between theoretical calculations and the experimental testing of surface residual stress is established. The results suggest that the surface with 10% biaxial compression can represent the surface state after shot peening with a 6 mm diameter steel ball. In addition, shot peening could increase the film formation rate of the Ti13Nb13Zr surface and effectively promote the formation of TiO2 nanotubes. Our findings show how the friction performance of TiO2 can be improved by using the residual stress on the surface and provide insights for the rational design of high-performance TiO2 biomedical materials.