Characterization of the surface layer modified in ti6-al7-nb alloys by plasma nitriding using cathodic cage

Abstract

Using titanium as the base metal of biomaterials has gained attention due to its excellent mechanical properties, biocompatibility, and resistance to corrosion and wear. In this research, Ti6-Al7-Nb (wt%) alloy has been superficially modified by cationic cathode plasma nitration (CCN) in order to improve the pre-existing biocompatible characteristics in the alloy. Four treatment conditions and a standard sample, for comparative purposes, were chosen. Nitriding was implemented using a cathodic cage technique at a different time and temperature conditions, and at constant pressure. Samples 1 and 2 were treated at a temperature of 300°C for 1h and 2h, while samples 3 and 4 were treated at 400°C for 1h and 2h, respectively. The characterization techniques used were: SEM, EDS, XRD, microhardness, and roughness. The results regarding SEM and EDS techniques revealed the formation of a TiO2 film for three samples. The XRD analysis showed the existence of a peak related to the formation of titanium nitride (TiN), in various proportions, for all analyzed samples. The formation of the film also confirms a hardness increase for conditions 1, 2 and 3. The analysis of the roughness demonstrated results for rounded peaks for samples 1, 2 and 4, where sample 4 revealed the lowest roughness value. In light of the results, it was possible to verify that the nitrided samples had their properties, partially or integrally, improved in relation to the standard one.