A study of the corrosion behaviour and protective quality of sputtered chromium nitride coatings

Nitride based hard coatings are widely used for mechanical applications. Among these coatings, chromium nitrides are especially interesting because they combine good tribological properties with relative chemical inertness. Corrosion-resistant nitrogen-doped chromium thin films were deposited by using an industrial magnetron reactive sputtering device. A precise control of the composition has permitted separate synthesis of the defined compounds that exist in the binary diagram Cr-N: Cr2N and CrN. Potentiodynamic methods were used to investigate the corrosion protection provided on AISI 304 stainless steel by various coatings. At the same time, coating microstructure was investigated by XRD and SEM/EDS as well as its tribological properties (hardness and wear resistance). The CrN coatings exhibit the higher wear resistance whereas the Cr2N films show the better hardness. Cr2N coatings or CrN coatings have an inert intrinsic behaviour either in acidic or in chloride solutions. However, their capability of protecting the substrate from any corrosion is limited due to defects and porosity. However, as a function of deposition parameters, these coatings can enhance the substrate lifetime in aggressive environments. (C) 2000 Elsevier Science S.A. All rights reserved.