Structure and properties of NbN/MoN nano-multilayer coatings deposited by magnetron sputtering

Abstract

NbN/MoN nano-multilayer coatings with MoN layer thickness ranging from 1.0 to 4.3 nm were deposited using a closed field unbalanced magnetron sputtering system by varying Mo target current. The structure of the coatings was investigated by X-ray diffraction, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. The mechanical and tribological properties of the coatings were evaluated by nano-indentation and ball-on-disc wear tests. It was found that all of the as-deposited NbN/MoN multilayer coatings exhibit fcc B1-NaCl structure and the preferred orientation of the coatings changed from (111) to (200) as MoN layer thickness exceeds 2.1 nm. The NbN/MoN multilayer coatings with MoN layer thickness 1.0 nm exhibit a superhardness with value of 40.0 GPa. Further increase of MoN layer thickness results in a decrease in coating hardness. The NbN/MoN multilayer coatings exhibit lower coefficient of friction and better wear resistance compared to NbN single layer coatings. A low COF of 0.53 and wear rate of 0.7 × 10−6 mm3/Nm can be achieved in the NbN/MoN multilayer coatings with a MoN layer thickness of 4.3 nm.