Ti/Ti-N Hf/Hf-N and W/W-N multilayer films with high mechanical hardness

TLDR

The authors developed Ti/Ti‑N, Hf/Hf‑N, and W/W‑N multilayer films with ultrathin metal and metal‑nitride layers to achieve hardness far exceeding that of single‑layer nitride films. The high hardness arises from grain size restriction in the thin layers, and the films were fabricated on room‑temperature substrates by a simple sputtering process. The multilayer films exhibited hardness between 3500 and 5000 kg mm⁻², surpassing the 2200–2800 kg mm⁻² typical of single‑layer films, and showed improved adhesion, fewer defects, and potential for hard‑coating applications.

Abstract

Ti/Ti-N, Hf/Hf-N, and W/W-N multilayer films with very thin individual metal and metal-nitride layers were developed, with hardness of the structure much higher than that of single-layer nitride films. Hardnesses with value between 3500 and 5000 kg/mm2 or higher were observed in the multilayer films. This is an improvement over that of single-layer metal-nitride films where hardnesses between 2200 and 2800 kg/mm2 are typically achieved. The improvement is thought to be due to the fact that the grains are restricted to a very small size in the thin individual layers of the sandwich structure. The multilayer films, in general, have better adhesion and less defects than the single-layer films. These films were prepared on room-temperature substrates by a simple sputtering process and have potential applications, as in hard coatings.