Thermal stability of PVD hard coatings

Hard coatings deposited by physical vapour deposition based on the transition metal nitrides are nowadays widely applied to reduce tool wear. The aim of this paper is to show how microstructural parameters like grain size, stress and chemical and phase composition influence the thermal stability of different hard coatings. This is demonstrated using single-phase coatings like TiN, (Ti, Al, V)N and CrN as well as the dual-phase nanocomposite coatings CrN-Cr₂N and TiN-TiB₂. It is shown that the resistance against recovery and recrystallization can be improved by introducing a high density of phase boundaries, as is the case for nanocomposite coatings.