CrN, CrN/SiC, and CrN/DLC Coatings Deposited by a Novel Arc Plasma Acceleration Process: Processing and Properties

CrN monolayers along with CrN/SiC and CrN/diamond-like carbon (DLC) duplex layers were deposited by arc plasma acceleration on 4340 steel substrates. The layers exhibit a dense microstructure with a low density of surface defects and macroparticles. The tribological properties were evaluated with dry ball-on-disk sliding tests against an alumina counterface at room temperature. The CrN monolayer exhibits a coefficient of friction, µ = 0.28 ± 0.02, while CrN/SiC and CrN/DLC duplex layers both demonstrate much lower µ = 0.07 ± 0.01. The wear rates of the coatings were very low and measured as 0.53, 0.73, and 0.79 µm3/Nm, respectively, for CrN, CrN/DLC, and CrN/SiC. Corrosion resistance was evaluated in both cyclical environmental testing as well as quantitatively via electrochemical impedance spectroscopy. The corrosion resistance in both cases is compared to standard electroless Ni and electroplated Cr coatings. The highest level of corrosion resistance was observed for the CrN monolayer and CrN/SiC duplex layer. Both exhibit improved corrosion resistance over electroless Ni and electroplated Cr coatings. This high level of corrosion resistance is remarkable for physical vapor deposited thin nitride layers. The arc plasma acceleration deposited materials show great promise for applications in which a combination of low friction, wear resistance, and corrosion resistance are required.