Structural, tribological and antibacterial activities of Ti–Cu–N hard coatings prepared by plasma surface alloying technique

In this work, Ti–Cu–N hard coatings were deposited on AISI316L stainless steel (SS) substrates by plasma surface alloying technique with a Ti–Cu alloy target. The morphology, composition and structure were investigated by SEM, GDOES and XRD. Microhardness and coating/substrate adhesion were analyzed by microhardness tester and scratch test. Tribological performance of the Ti–Cu–N coatings and SS substrate was investigated by using ball-on-disk tribometer. The viability of bacteria attached to the antibacterial surface was tested using the spread plate method. The results indicated that the concentration of Ti and Cu gradually decreased from the surface coatings to substrate, and the maximum copper concentration in the alloyed surface was about 20 wt.%. X-ray diffraction analysis showed that the coatings were composed of TiN and copper crystalline phases. Scratch test showed that the Ti–Cu–N coatings possessed good adhesion with the substrate. The microhardness of the Ti–Cu–N coatings was about 1030 HV0.025, which was about 4.5 times as much as that of the SS substrate. Wear resistance of the Ti–Cu–N coatings was improved obviously during the sliding tests against GCr15, and showed micro-abrasion wearing. The Ti–Cu–N coatings exhibited excellent antibacterial ability, and an effective reduction of 99.9% of Escherichia coli (E. coli) within 12 h was achieved by contact with the alloyed surface, which may be attributed to the release of copper ions when the Ti–Cu–N coatings in contact with bacterial solution.