• VN/TiN−Ni nano-multilayered films with a deposition time ratio of 10:12 achieve a hardness of 25.9 GPa, elastic modulus of 317 GPa, and fracture toughness of 1.88 MPa·m1/2.
• Fracture toughness is improved by approximately 50% compared to monolithic VN films, attributed to coherent interfaces and phase separation in the TiN−Ni layer.
• The TiN−Ni layer grows epitaxially on the VN layer, forming a coherent interface that enhances mechanical properties.
• Modulation layer thickness critically influences the microstructure and mechanical behavior of the nano-multilayered films.