Wear and corrosion resistance of CrN/TiN superlattice coatings deposited by a combined deep oscillation magnetron sputtering and pulsed dc magnetron sputtering

Deep oscillation magnetron sputtering (DOMS) is a novel high power impulse magnetron sputtering technique, which offers large voltage oscillation packets to generate a stable high-power discharge plasma with high ionization under virtually arc-free conditions. CrN/TiN superlattice coatings were deposited using a combined DOMS and pulsed dc magnetron sputtering (PDCMS) in a closed field unbalanced magnetron sputtering configuration. The Cr target was powered at 400W by DOMS and Ti target was powered at 2000W by PDCMS. The negative substrate bias (V-s) ranged from 0 V to -100 V. As the V-s was increased, CrN/TiN superlattice coatings showed a single phase face-centered cubic structure with a strong (111) texture. Correspondingly, the coatings exhibited the dense microstructure with well-defined interfaces between CrN and TiN layers. The increase in V-s led to a decrease in grain size and an increase in the compressive residual stress. The hardness and Young's modulus of the coatings increased with increasing V. The H/E* and H-3/E*(2) ratios and critical loads L-C in scratch test showed an initial increase, followed by a decrease. The wear mechanism changed from severe adhesion wear to abrasion wear. The coating deposited at V-s = -60 V exhibited mild abrasion wear with the lowest friction coefficient of 0.27 and the lowest specific wear rate of 0.5 x 10(-6) mm(3) N-1 m(-1) due to high hardness, H/E* and H-3/E*(2) ratios, L-C1 and L-C3 of 36 GPa, 0.094, 0.316, 15.3N and 24N, respectively. The coatings also exhibited increasing pitting corrosion resistance with lower current density and higher corrosion potential in 3.5 wt% NaCl aqueous solution. Combined DOMS + PDCMS techniques can provide the engineering surfaces for the industrial applications with the combined improvement in wear and corrosion resistance. (C) 2015 Elsevier B.V. All rights reserved.