Tribo-corrosion performance of filtered-arc-deposited tantalum coatings on Ti-13Nb-13Zr alloy for bio-implants applications
Tantalum coatings were deposited on Ti-13Nb-13Zr alloy by filtered cathodic vacuum arc deposition in order to improve the alloy's wear and corrosion resistance under load-bearing, biomedical applications. The Ta coating exhibits an amorphous structure, which transforms into a mixture of alpha and beta phases as the substrate is heated to 300 °C during deposition. Tribo-corrosion tests were performed using a ball-on-disk tribometer under simulated joint fluid at 37 °C by sliding the uncoated and Ta-coated surfaces against alumina balls. The Ta coatings showed a significant reduction in the coefficient of friction under these test conditions. The wear rates of the Ta-coated disk surfaces are slightly lower than those of the bare Ti-13Nb-13Zr alloy, while the wear rate of the alumina balls was one order of magnitude higher when it slid against the Ta-coated samples than when it was slid against the Ti-13Nb-13Zr alloy. The wear debris generated from the Ta-coated samples sliding against alumina was comparatively smaller than that generated by the uncoated alloy against alumina. The wear characteristics of the Ta coatings do not favour using such coatings on implant materials. The Ta coatings exhibited a strong capacitive response which is proposed to enhance corrosion protection of the Ti-13Nb-13Zr alloy.