Control of microstructures and properties of dc magnetron sputtering deposited chromium nitride films

Chromium nitride coatings have been prepared by a conventional DC magnetron reactive sputtering process in nitrogen–argon mixed atmospheres. The sputtering pressure and target voltage versus nitrogen flow rate curves were established in order to control the structures and properties of chromium nitride coatings. A good correspondence among the sputtering pressure, target voltage evolutions and the phase developments with respect to nitrogen flow rate has been found. The stoichiometric Cr2N and CrN coatings were confirmed by EPMA and XRD analysis. Cryogenic fracture cross-section SEM images show columnar growth morphologies. Stoichiometric chromium nitrides present high hardness and elastic modulus as well as high H3/E2 ratio in a nano-indenter test. Adhesion and tribological properties were evaluated by scratch and pin-on-disk tests, respectively. Chromium nitrides present normal adhesion failure critical load (Lc2) between 10 and 20 N and friction coefficients ranging from 0.5 to 0.75.