Pinning growth of TiN films toward porous Ti matrix

Golden-TiN materials have attracted significant attentions as functional films in cutting tools and decoration surface due to its colored surfaces, ultra-high hardness, superior corrosive resistance, etc. With regards to its poor surface toughness, low interfacial adhesion and tedious technological procedures, challenges involved in TiN films have seriously restricted the scope of engineering applications. Herein it is generally considered that constructing honeycomb-like porous Ti matrix by anodizing was expected to support more adsorbing space for N₂ gas through nano-pores. Meanwhile, the long-term isothermal aging treatments were used to motivate [Ti] + [N]_ad. → TiN chemical bonds, facilitating the pin-holes growth of TiN along the as-anodized nano-pores. Meanwhile, different aging temperature at 500, 600 and 700 °C in air was used to assess chemical composition and properties of TiN films. As a consequence, results manifested that a low-purity TiN film with pyramid-like texture was successfully achieved under isothermal aging at 600 °C for 3 h at 0.8 MPa N₂ gas pressure, also depicting an increasing interfacial strength of ~ 39.5 N from scratch tests for TiN-Ti films due to in-deep diffusion by TiN pinning growth. In view of tribological tests that the friction coefficient of TiN film was in a much lower range of 0.2 ~ 0.3 and its lowest value of wear rate was 1.1 × 10^–4 mm³/(N·m) for TiN films at 600 °C, which was reduced by 50% compared to bare Ti substrate. Overall, an effective and well-designed approach was carried out for TiN-Ti gradient films on porous Ti surface, thus creatively proposing a concise way for low-purity TiN films within excellent mechanical properties to satisfy the most requirements of engineering devices without high costs.