Air-based sputtering deposition of TiN(O)/a-TiNxOy multilayer films for enhanced mechanical properties and corrosion resistance

Extensive research has explored multilayer films for their distinctive mechanical and functional properties. This study employs an air-based sputtering technique, using air as a reactive gas under low vacuum conditions, to produce TiN(O)/a-TiNxOy multilayer films. By alternately adjusting the air/Ar flow ratios, the multilayer films with various modulation periods were created. The crystalline TiN(O)/amorphous TiNxOy multilayered structure was confirmed via cross-sectional microscopy and electron energy loss spectroscopy images and mappings. Hardness (H) and elastic modulus (E) initially increased, peaked, and then decreased with the modulation period, reaching a maximum hardness of 31.2 GPa and an elastic modulus of 343 GPa. The enhancements may be attributed to internal compressive stress, interface strain effects, and the inhibition of dislocation propagation throughout the films. Higher H/E ratios (0.09–0.11) and H3/E2 ratios (0.23–0.28 GPa) suggest enhanced resistance to elastic and plastic deformation, surpassing those of single-layered TiN(O). This enhancement is primarily attributed to the hard/soft multilayer design. Potentiodynamic polarization tests revealed improved corrosion resistance with decreasing modulation period, reaching optimal values Ecorr at −0.089 V and Icorr at 0.272 μA/cm2. This improvement is mainly ascribed to the multilayer design, which inhibits direct corrosion through grain boundaries. This air-based sputtering technique offers a facile approach for producing complex multilayer films, promising enhanced mechanical properties and corrosion resistance of coatings for various applications.