High temperature oxidation behavior of a sputtered pure Ni nanocrystalline coating at 700-900 °C

A nanocrystalline coating of Ni was deposited on a pure Ni substrate via magnetron sputtering. The oxidation behavior of the Ni substrate and the nanocrystalline coating was studied in air at 700-900 °C. The samples were examined by scanning tunneling microscopy, scanning electron microscopy with energy dispersive X-ray and X-ray diffraction. The mass gain in the coated sample was higher than that without the coating. The study showed that the nanocrystallization in pure Ni promoted oxidation during early stage, after that, the oxidation rates are about the same in samples with or without the nanocrystalline layer. The oxidation mechanism was also discussed.