Fatigue durability and corrosion resistance of TiO2 films on CoCrMo alloy under cyclic deformation

Smooth and dense TiO2 films with different thickness (45 nm and 300 nm respectively) were deposited on a flat CoCrMo substrate by high power impulse magnetron sputtering (HiPIMS). A cantilever resonance method was developed to load cyclic stress on the sheet samples to investigate the fatigue durability of the TiO2 films. The evolution of pre-cracks, which were introduced intentionally in the TiO2 films, was studied at the same time. After cyclic deformation, the corrosion resistance of the TiO2 film coated CoCrMo alloy was investigated by potentiodynamic polarization tests. The results showed that there were no peelings, cracks or delamination of both film types after 1.08 × 107 loading cycles with the maximum stress of 200 MPa. For the evolution of the pre-cracks in the thicker TiO2 films (300 nm), new cracks emerged near the pre-cracks in the films, while for the pre-cracks in the thinner TiO2 films (45 nm) not any new cracks were observed. The thinner films seemed to show better fatigue durability than thicker films. The potentiodynamic polarization tests revealed that the corrosion resistance of the thinner TiO2 films (45 nm) was not degraded even after 1.08 × 107 loading cycles with the maximum stress of 20 MPa.