The Investigation of NiTi Tribological Behaviour in the Body Simulated Environment

Alloys based on NiTi are now widely used for biomedical applications due to such unique properties as superelastisity and shape memory effect. Recent research has also revealed that this material also has good tribotechnical properties and its wear resistance was reported to be 3-30 times higher in comparison with titanium alloys and medical grade steels. However in most experiments NiTi was predominantly tested against dissimilar materials like tungsten carbide. At the same time tribotechnical behaviour of NiTi against titanium alloys especially in the body simulated fluids are much less investigated, whereas this information could be useful for the designing of some medical devises.

In the present work we studied tribotechnical behaviour of NiTi (55.8wt.Ni, A_f=35⁰C) against Ti-6Al-4V alloy. The influence of diamond-like (DLC) and TiN coatings deposition on the wear resistance of this friction pair was also investigated. Tests were conducted using ball-on-disc configuration at the frequency 1 Hz, P=10N, reciprocation movement, amplitude 12 mm using diluted calf serum as a lubricant.

It was revealed that in the described conditions NiTi against Ti-6Al-4V alloy friction pair has just 2-3 times less volume wear loss in comparison with Ti-6Al-4V/Ti-6Al-4V friction pair (10.5 and 31.8 mm³ correspondingly, sliding distance 15.3 km). It was found that the deposition of DLC and TiN coatings significantly reduces volume wear of both counter-bodies. As a result the volume loss of the whole friction pair was found to decrease 45-50 times in comparison with the initial state.