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

The generation of wear particles is now considered one of the most important failures in total arthroplasty. It is especially needed to study damage process of the particles at slight movement and lower load for long-term service of implanted materials. The wear and abrasion behavior of particles on Ti-6Al-4V coated with diamond-like carbon (DLC) were appropriately simulated in the present paper by fretting wear and nano-scratch test. The coatings with a thickness of 2.5 mum were deposited with an r.f.-plasma enhanced chemical 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 coatings were performed using a Nano Indenter XP system with attachments of continuous stiffness measurements (CSM) and lateral force measurements (LFM). Tribological properties of the coatings were evaluated by a fretting wear test. 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 recovered fully elastic at lower load (60 mN) and were ploughed and delaminated only partially at higher load (400 mN). Nevertheless, there was wear debris concurrently generated during the nano-scratch and fretting test, which was more evident at high loads for a definite coatings, indicating an essential necessity of the work to improve the wear resistant of the coatings to avoid the generation of wear debris. The friction coefficient of DLC coatings against corundum obtained by fretting test decreased with the increase of relative humidity, it was below 0.1 in an aqueous condition, this may be beneficial to their biomedical applications in body fluids. (C) 2001 Elsevier Science B.V. All rights reserved.