Nano-scratch and fretting wear study of DLC coatings for biomedical application

The generation of wear particles is now considered one of the most importan t failures in total arthroplasty. It is especially needed to study damage p rocess of the particles at slight movement and lower load for long-term ser vice of implanted materials. The wear and abrasion behavior of particles on Ti-6Al-4V coated with diamond-like carbon (DLC) were appropriately simulat ed in the present paper by fretting wear and nano-scratch test. The coating s with a thickness of 2.5 mum were deposited with an r.f.-plasma enhanced c hemical vapor deposition method. The analytic techniques employed to assess DLC coatings characterization include SEM, ATM, Raman and IR spectroscopy. Assessment of hardness, elastic modulus, abrasion and adhesion of the coat ings were performed using a Nano Indenter XP system with attachments of con tinuous stiffness measurements (CSM) and lateral force measurements (LFM). Tribological properties of the coatings were evaluated by a fretting wear t est. It was concluded that the DLC coatings had a smooth surface morphology with a rms of 6.8 nm and possessed good adhesion to the substrate, they re covered fully elastic at lower load (60 mN) and were ploughed and delaminat ed only partially at higher load (400 mN). Nevertheless, there was wear deb ris concurrently generated during the nano-scratch and fretting test, which was more evident at high loads for a definite coatings, indicating an esse ntial necessity of the work to improve the wear resistant of the coatings t o avoid the generation of wear debris. The friction coefficient of DLC coat ings against corundum obtained by fretting test decreased with the increase of relative humidity, it was below 0.1 in an aqueous condition, this may b e beneficial to their biomedical applications in body fluids. (C) 2001 Else vier Science B.V. All rights reserved.