Mechanical and tribological properties of CrN/TiN multilayer coatings deposited by pulsed dc magnetron sputtering

• CrN/TiN coatings were synthesized at various Cr target powers of 70–1000 W.
• At 400 W, the coating showed the best mechanical and tribological properties.
• The coatings showed high HF levels and LC due to high H/E* and H3/E*2 ratios.
• Tribological properties were related to H/E* and H3/E*2 ratios and residual stress.
• Increased stress-related LC3 led to oxidative wear changing from severe to mild.

CrN/TiN multilayer coatings were deposited by pulsed dc magnetron sputtering (PDCMS) in a closed field unbalanced magnetron sputtering system. The Ti target power was maintained at 2000 W while the Cr target power was varied from 70 to 1000 W. As the Cr target power was increased, CrN/TiN multilayer coatings with the Cr/(Cr + Ti) ratio of 0.037–0.573 had a single phase face-centered cubic structure with a texture evolution from (111) to (220). The residual stress of the coatings increased from − 1.03 GPa to − 5.65 GPa. The hardness and the H/E* and H3/E*2 ratios of the coatings exhibited an initial increase with the increasing Cr target power, then followed by a decrease. The coating with a Cr/(Cr + Ti) ratio of 0.30 reached the highest hardness and the H/E* and H3/E*2 ratios of 31 GPa, 0.0832 and 0.214, respectively. The coating also showed a dominant oxidative wear with the lowest friction coefficient and specific wear rate of 0.41 and 2.3 × 10− 6 mm3 N− 1 m− 1, respectively. The increase in the H/E* and H3/E*2 ratios led to the increase in the toughness and cohesion/adhesion strength of the coatings with the increased HF levels and critical loads (LC1, LC2 and LC3). However, the coatings with similar H/E* and H3/E*2 ratios exhibited different tribological properties due to the different critical loads LC3 resulted from the increased compressive residual stress. The improvements in toughness and cohesion/adhesion strength promoted the reduction in the crack initiation and propagation, and oxidative wear during dry sliding tests.