Deposition of NbN thin films onto high-speed steel using reactive magnetron sputtering for corrosion protective applications

Hard niobium nitride films were deposited onto high-speed steel (HSS) using reactive magnetron sputtering. Experiments were carried out by varying the nitrogen partial pressure. The porosity and corrosion behavior of the NbNx/HSS samples were studied by a copper decoration test and by potentiodynamic corrosion tests in 0.8 M NaCl solution (pH 7), respectively. The corrosion tests revealed that the NbN/HSS system has a very broad passivation range with a low current density. Further film properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), scratch testing and microhardness measurements. Good adhesion and very high plastic universal-hardness values in the range of 34 000–53 000 N/mm2 were found for the NbN thin films.