Superhard V-Si-N coatings (>Â 50Â GPa) with the cell-like nanostructure prepared by magnetron sputtering

By using reactive magnetron co-sputtering deposition, we prepared V-Si-N coatings from a pulsed-DC-excited vanadium source and an RF-DC-coupled Si source. The process was run at 773 K under a relatively high partial pressure of nitrogen (0.3 Pa) and generated intense ion bombardment at the substrate (Ji/JMe ~ 4.5). These favorable process conditions led to the formation of dense and smooth V-Si-N coatings with high hardness values (> 33 GPa). We performed high-resolution transmission electron microscopy (HRTEM) studies for the coating with 5.5 at.% Si and identified a cell-like nanostructure, in which nanocrystalline VN grains were encapsulated by < 1-nm-thick silicon nitride layers. This cell-like nanostructure, together with an extremely dense and featureless growth structure, rendered the 5.5 at.% Si coating > 50 GPa nanoindentation hardness and > 80% elastic recovery.