Microstructures and corrosion behaviors of Zr modified CrN coatings deposited by DC magnetron sputtering

Zirconium modified chromium nitride coatings with various Zr contents have been prepared by a DC reactive magnetron sputtering technique. The detailed investigations in terms of composition, phase structure, morphology and corrosion properties have been performed by GDOES, XRD, SEM and electrochemical measurements, respectively. The as-deposited coatings with Zr contents ranging from 0 to 3.2 at. % form nanocrystalline solid solutions, where Zr substitute Cr in the CrN lattice. With increasing Zr contents, the lattice parameters increase but the grain sizes show little effects. All the coatings exhibit dense compact columnar structures in SEM cross-sectional observations. Electrochemical measurements in 3.5% NaCl solutions revealed that the additions of Zr into CrN coatings improved their chemical inertness. The coated samples with much low corrosion current densities in nA/cm2 range show their excellent protective characteristics to the stainless steel substrates. The corrosion mechanism, however, was due to the slight pitting corrosions, which were mainly localized in the growth defects.