Structure and antibacterial properties of CrN-Cu coating with the discontinuous Cu layers by multi-arc ion plating

The CrN-Cu coatings were synthesized on titanium substrates via multi-arc ion plating. A discontinuous Cu layer was successfully incorporated into the CrN coating by controlling the deposition parameters to improve the coating structure and endow the coating antibacterial properties. The total thickness of the CrN-Cu coating was 5.53 μm. The CrN-Cu coating consists of two phases, CrN and Cu, with a discontinuous Cu layer in the form of clusters surrounded by differently oriented CrN grains. X-ray photoelectron spectroscopy revealed the chemical bonding states of Cr-N and Cr-O, as well as those of metallic copper and copper oxide. The addition of copper reduced the residual compressive stress from 1.49 GPa to 1.00 GPa, increased the interfacial bond strength (critical load LC3 from 28.62 N to 61.73 N), and reduced the coefficient of friction from 0.43 to 0.38. Despite the slight decrease in nanohardness owing to the soft copper interlayer, the coating demonstrated excellent antibacterial efficacy owing to the controlled release of copper ions (0.240 mg/L after 24 h of immersion), reaching 99.75% and 99.87% for E. coli and S. aureus, respectively.