Thermal stability, mechanical and corrosion behaviour of niobium-based coatings in the ternary system Nb–O–N

The influence of oxygen in the system Nb–O–N on properties like thermal, mechanical, corrosion and degradation behaviour was studied with respect to the O/N ratio in the films prepared by reactive magnetron sputtering. With increasing O/N ratio the hardness, the Young's Modulus and the residual stress strongly decreased. Furthermore the friction coefficient decreased in pin-on-disk tests against a 100Cr6 ball and was lowest for NbON coatings with medium oxygen content. The thermal stability in vacuum was excellent for the coatings up to 800 °C except for coatings with an O/N ratio of ≥ 12.8. These high oxygen-containing coatings crystallised at about 600 °C. The corrosion resistance of the Nb-based coatings in NaCl-containing media strongly improved with increasing O/N ratio, presumably due to the amorphous structure of the oxygen-containing coatings.