Surface treatment by electric discharge machining of Ti–6Al–4V alloy for potential application in orthopaedics

This study investigated the properties of Ti–6Al–4V alloy after surface treatment by the electric discharge machining (EDM) process. The EDM process with high peak currents proved to induce surface macro-roughness and to cause chemical changes to the surface. Evaluations were made of the mechanical properties by means of tensile tests, and of surface roughness for different peak currents of the EDM process. The EDM process with peak current of 29 A was found to induce sufficient surface roughness, and to have a low adverse effect on tensile properties. The chemical changes were studied by scanning electron microscopy equipped with an energy dispersive X-ray analyser (EDX). The surface of the benchmark samples was obtained by plasma-spraying a titanium dioxide coating. An investigation of the biocompatibility of the surface-treated Ti–6Al–4V samples in cultures of human osteoblast-like MG 63 cells revealed that the samples modified by EDM provided better substrates for the adhesion, growth and viability of MG 63 cells than the TiO2 coated surface. Thus, EDM treatment can be considered as a promising surface modification to orthopaedic implants, in which good integration with the surrounding bone tissue is required.

► EDM process with optimised peak current of 29 A to impose surface roughness.
► Experiments: mechanical tests, SEM, biocompatibility and cell viability tests.
► Carbon enriched surface layer was observed on EDM-treated samples.
► EDM processed surface is optimum for the adhesion and growth of human bone cells.