Mo 2N/Cu thin films — the structure, mechanical and tribological properties

• Published in: Surface & coatings technology Vol. 200; no. 22; pp. 6288 - 6292
• Main Authors: Suszko, T., Gulbiński, W., Jagielski, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2006
• Subjects: Copper; High temperature friction; Magnetron deposition; Microhardness; Molybdenum nitride; Nanocomposite; Tribological properties; Molybdenum nitride; Tribological properties; Magnetron deposition; Nanocomposite; Copper; Microhardness; High temperature friction
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2005.11.041

Thin, nanocomposite films of copper doped molybdenum nitride (γ-Mo 2N) were deposited by double source, reactive magnetron sputtering. Their structure, microhardness and tribological properties in the wide temperature range (20–400 °C) were studied. An addition of copper results in the refinement of nitride crystallites from 12 nm for pure Mo 2N to the level of 6 nm for copper content close to 22 at.%. At low copper concentrations (around 1–3 at.%) slight increase of microhardness has been observed. Free, metallic copper phase has not been identified in diffraction patterns up to the highest concentrations (22 at.%). Most probably copper is dispersed at the grain boundaries in form of nano-clusters with the size below the X-ray diffraction limit. Tribological properties of molybdenum nitride films depend on copper content. It is particularly visible during 100 °C sliding tests. At that temperature the wear rate decreased significantly for copper concentration higher than 6 at.%. Simultaneously, the oxidation rate of this nanocomposite material seems to be promoted by copper. However, the oxidation product containing MoO 2, MoO 3 and traces of copper molybdate CuMoO 4, shows much better adhesion to the native coating than pure molybdenum oxide.