Tribological behaviour of duplex treated Ti-6Al-4V: combining nitrogen PSII with a DLC coating

摘要

The chemical structure and tribological behaviour of Ti-6Al-4V plasma source ion implanted with nitrogen then DLC-coated in an acetylene plus hydrogen-glow discharge (bias voltage - 10 to - 30 kV) were investigated. The as-modified samples have aTiNIH:DLC multilayer architecture (coating resistivity 1.6×10{sup}9 to 2.4×10{sup}11Ω/cm) and exhibit higher hardness, especially at low loads or plastic penetrations in the order of deposition bias voltage - 10, -20 and - 30 kV. At a lower contactload (1 N) and higher sliding speed (0.05 m/s), frictional properties in most cases improved, as did wear properties. At a higher contact load (5 N) and lower sliding speed (0.04 m/s), friction showed almost no improvement, and wear propertiesdeteriorated. When the material of the counterbody was then changed from AISI 52100 to Ti-6Al-4V modified as the disc (contact load 5N unchanged, sliding speed decreased), the friction coefficient decreased (but showed no improvement compared with theunmodified sample), while wear properties deteriorated further, and wear was changed from just the disc to both disc and ball, abrasive and adhesive dominated. Transfer films, mainly made up of wear debris transferred from the disc wear surfaces, wereformed on the wear scars of the counterbodies. The deterioration of wear properties of the modified samples at the higher contact load is considered to be caused by the "thin ice" effect.