Ultrasonically nanostructured electric-spark deposited Ti surface layer on Ti6Al4V alloy: enhanced hardness and corrosion resistance

A complex approach for the production of corrosion resistant nanostructured surface layer on the Ti6Al4V alloy is reported in this article. Surface modification was conducted using sequential application of electric discharge surface alloying (EDSA) with α-titanium and ultrasonic impact treatment (UIT) induced the nanostructuring of the EDSA-formed Ti-layer. X-ray diffraction and TEM analysis show that the applied modifications form the outmost surface layer of ~20 μm thick comprised the nanoscale grain structure with a grain size of 10-30 nm. Additionally, the UIT-induced mechanochemical oxidation of the modified surface was observed by SEM with energy dispersive X-ray microanalysis. The produced nanostructured α-titanium surface layer shows enhanced microhardness and better corrosion behaviour in saline solution than those of the original and UIT-processed Ti6Al4V alloys. Thus, the complex treatment applied can be recommended for the surface finishing of the products made of multi-phase titanium alloys, such as biomedical implants.