Tribological behavior of uncoated and DLC-coated CoCr and Ti-alloys in contact with UHMWPE and PEEK counterbodies

• Zr-DLC presented better adhesion and low residual stress compared to DLC coatings.
• No significant differences were found in the wear of UHMWPE for all material combinations.
• Zr-DLC and DLC coatings delaminated when tested against PEEK counterbodies.
• The presence of biological fluids together with high cyclic shear stress caused interface fatigue.

There are very few studies of PEEK wearing against DLC. In this study, DLC and Zr-DLC coatings were deposited by magnetron sputtering onto Ti alloy substrates. Coated and un-coated Ti alloy samples were tribologically tested in multidirectional pin-on-disk equipment against UHMWPE and PEEK. CoCr alloy was also tested as control. Each of the materials was tested for 2 million cycles (Mc) in bovine serum lubricant (37 °C). Gravimetrical weight loss and changes in surface profile were similar when tested against UHMWPE. However, Zr-DLC samples delaminated after 1.2 Mc. When tested against PEEK, both coated samples delaminated, despite that the coatings maintained their structural integrity. The synergetic effect of stress-induced corrosion through biological fluid and high cyclic shear stress may have caused interface fatigue and subsequent delamination of both coatings.