Wear-corrosion characteristics of unimplanted and nitrogen-implanted Ti-6A1-4V alloy

Unimplanted and nitrogen–implanted Ti–6A1–4V was subjected to what were believed to be wear/corrosion conditions in an environment simulating body fluids, and tests were designed to measure separately the wear and corrosion components. These tests were unsuccessful because when cathodic polarization occurred via hydrogen ion reduction (or when cathodic protection was used to prevent corrosion), the formation of titanium hydride prevented meaningful measurements. Likewise, if cathodic polarization occurred via reduction of dissolved oxygen, rapid repassivation introduced an undesired complication into the scheme of events. However, anodic dissolution tests conducted under wear conditions at an imposed potential of +0.4V (SCE), within the passive range, showed dissolution rates which correlated very well with implanted microstructures. A fluence of lxl022 nitrogen atoms m−2 gives a microstructure consisting almost entirely of titanium nitride, and the wear, corrosion, and wear/corrosion properties are judged to be excellent. Lower fluences give less desirable properties.