Nanostructured molybdenum nitride-based coatings: Effect of nitrogen concentration on microstructure and mechanical properties
School of Engineering
ARC Number : DP150102417
Molybdenum nitride (MoNx) coatings were deposited onto AISI M2 tool steel substrates (hardened to HRC 60) by magnetron sputtering. The nitrogen content was controlled by means of a closed-loop optical emission monitor. The coating microstructure was examined by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. This showed that the increased nitrogen content led to a transformation from body-centered cubic α-Mo phase to γ-Mo2N phase (NaCl-B1 type) and then to a face-centered cubic MoN phase. The mechanical and tribological properties of these coatings were evaluated by nano-indentation, wear and scratch testing. The γ-Mo2N coating showed the highest hardness and the highest values of H (hardness)/E* (effective elastic modulus) and H3/E* ratio. During scratch and wear tests, the γ-Mo2N coating exhibited the best resistance to deformation and the lowest wear rate.