Superhard metallic coatings

Abstract The letter reports on the surface hardening of bulk soft metal materials by protective coatings made of the same metal as bulk but with up to 6 times higher hardness than that of the bulk material. This surface hardening is demonstrated by covering of the Ti substrate with a low hardness H bulk  ≈ 5 GPa by a 1200 nm thick Ti coating with a high hardness H coating  ≈ 30 GPa. The protective hard Ti coatings were sputtered by a new sputtering technology based on extremely high pressures (≥1000 GPa), high temperatures exceeding the melting temperature T m of the coating material and extremely high cooling rate of the created coating (≥10 10 K/s). The principle of this technology realized at an atomic level is described in detail.