Thin films of Mo2N/Ag nanocomposite—the structure, mechanical and tribological properties

Abstract Thin films of Mo2N/Ag composites were deposited on steel substrates by the reactive, double source magnetron sputtering. Their structure, chemical and phase composition were examined by X-ray diffraction, EDS/WDS analysis and scanning microscopy. Raman microscopy was used for the local phase identification at the coating surface after high temperature tribological tests carried out up to 400 °C in laboratory air of normal humidity. An addition of silver induced pronounced Mo2N crystallite size refinement accompanied by the slight hardness increase with the maximum at 2.5 at.% of Ag content. An addition of silver led also to the nitride lattice deformation and its partial transformation into β-phase. Except the room temperature tribological tests, where the soft metal addition resulted in an increase of friction, silver plays a positive role manifesting in friction coefficient reduction. After 400 °C friction tests, the silver molybdate phase, Ag2Mo4O13, has been found in the oxide scale covering silver rich (> 15 at.% of Ag) composite coatings. Hardness and tribological properties of Mo2N/Ag composite coatings are discussed in terms of their structure and the phase composition.