Structural-phase and stressed state of vacuum-arc-deposited nanostructural Mo–N coatings controlled by substrate bias during deposition

The effect of substrate bias on the structural-phase and elastic stress-strained state during the formation of vacuum-arc-deposited nanostructural coatings of the Mo–N system has been studied. An increase in the bias potential leads to (i) predominant [111] orientation of the growing molybdenum nitride crystals with a NaCl-type cubic lattice ($\gamma$-Mo$_2$N phase) and (ii) the appearance of a second phase with a body-centered cubic crystal lattice that is characteristic of pure molybdenum. The elastically strained (stressed) state of the coating is determined not only by the conditions of deposition, but also by the mechanical properties of a substrate. In order to provide for formation of coatings in a high-elastic-strained (stressed) state, it is necessary to deposit coatings onto substrates with high elastic moduli, which prevent metal flow at the interface. These highly stressed coatings with grain sizes within 9–14 nm possess high hardnesses that reach up to 45–50 GPa.