Studies On The Bioactive Ceramic Coatings On Ti6Al4V Alloys By Micro-arc Oxidation

In recent years, Orthopedic diseases brought great suffer to patients. Joint replacement surgery is an effective method of disease treatment. The important work of scientists is research and development artificial joint implants, which can improve the life quality of patients. At present, because of Ti-6A1-4V alloy has small elastic modulus, high strength, good biocompatibility, non-toxic, non-magnetic and other excellent performance, it become the most commonly used medical metallic material. But Ti-6A1-4V alloy are biologically inert material, It is still insufficient in the application process. its surface need to be modified.The porous biological ceramic coating containing Ca and P element was fabricated in electrolytic solutions by micro-arc oxidation technology on biomedical Ti-6AI-4V alloys.In this paper, the effect of electrolyte system and electrical parameters for micro-arc oxidation ceramic coating microstructure morphology and elemental composition of the coating were systematic study.The results show that:the best recipe for electrolyte is as follows:K2HPO4·3H2O 6.8 g/L, Ca(CH3COO)226.5 g/L, EDTA-2Na 20 g/L, Na2SiO36 g/L; corresponding optimal electrical parameters is as follows:current density 10A/dm2, pulse frequency 650Hz, oxidation time 10min. The micro-arc oxidation ceramic coating by this process conditions has high surface porosity, best wear resistance and corrosion resistance, best biocompatibility, porosity up to 14.93% and Ca to P atomic ratio of 1.71, which is very close to that of HA (1.67).Micro-arc oxidation ceramic layer was mainly composed of anatase TiO2 and rutile TiO2. Calcium concentration slightly affects the porosity of the film and the atomic ratio of Ca to P. Adding EDTA-2Na to the electrolyte, Ceramic coating has higher surface porosity and bigger aperture than before. The optimal concentration of EDTA-2Na was 20 g/L.Compared to four different electrolyte system, The micro-arc oxidation coating that produced in the solution of Na2SiO3 system has excellent properties. Experiments conducted in the same electrolyte system. As the current density increased, the pulse frequency reduced and oxidation time increased, the relative content of rutile TiO2 in ceramic coating increase, the film porosity and pore size increase initially and then decrease.When current density kept at 10 A/dm2, frequency kept at 650 Hz and reaction time from 5 min to 10 min, the best wear and corrosion resistance were obtained.