Tribomechanical Properties of a Carbon-Based Nanolayer Prepared by Nitrogen Ion Beam Assisted Deposition for Finger Joint Replacements

This paper presents the tribomechanical test results of Ti6Al4V alloy modified by carbon-based nanolayers with a thickness of 20 nm and 40 nm, prepared by nitrogen ion beam assisted deposition. The presence of carbon and nitrogen compounds was observed in the modified surface after ion bombardment. Nonstoichiometric TiNx was mainly detected near the interface nanolayer/titanium substrate and in the substrate itself. Ion bombardment led to an improved surface hardness of ~13 GPa in comparison to unmodified Ti6Al4V titanium alloy (~5.5 GPa) and alloy coated by carbon nanolayer without nitrogen ion assistance (~7 GPa). The decreasing of friction coefficient was achieved from 0.5–0.6 for untreated Ti6Al4V alloy to 0.1 for treated Ti6Al4V alloy. Wear testing using a joint wear simulator proved that the modified Ti6Al4V alloy has a higher resistance compared to the unmodified Ti6Al4V alloy. The primary local wear fault of the treated surface was observed after 240,000 cycles in comparison to enormous wear on the untreated surface after just 10,000 cycles. Treating the Ti6Al4V load-bearing components of implants with carbon-based nanolayers assisted by nitrogen ions is very promising in terms of extending the lifetime of implants and thereby reduces patient burden.