Preparation Of Micro-arc Oxidated Ceramic Coating On Titanium Alloy And Deposition And Conversions Of Hydroxyapatite

In the research field of biomedical implant material, titanium alloy substrate surface bioactivity ceramic coating have been paid an attention, while Hydroxyapatite is considered to be suitable for surface coating of this complex materials because its excellent biologic specialities. This type of complex materials can utilize both mechanical properties of substrate and bioactivity and biocompatibility of HA.In this paper, the process that relate to micro-arc oxidation technology, electro-deposition technology, as well as alkali treatment conversion principle of Ca and P elements is tried in order to prepare the coating which has good combination with the substrate and is rich in HA content on the surface of TC4 titanium alloy. And that using analyses methods such as SEM, EDS, XRD etc, the influence of the process condition on the morphology, chemical composition and the phase structures of ceramic coating is studied.The results show that, in the ion electrolyte whit felicitous and using the electrical parameters of micro-arc oxidation matching the electrolyte, a ceramic coating with rich Ca and P elements can be obtained. The proper formula of electrolyte is as follows: calcium acetate 0.36 mol/L, sodium glycero-phosphate 0.16 mol/L. The corresponding technical parameters are as follows: positive voltage 400V, negative voltage 80V, pulse frequency 800Hz, processing time 15 minutes. Under this condition, the prepared ceramic coating has a porous morphology on the surface, and Ca, P elements are relatively high in ceramic coating, moreover, the content ratio of Ca and P element is by 1.8 close to that of HA.HA can be deposited on micro-arc oxidation ceramic coating by using direct current pulse power in the conductive solution contains HA particles. The most deposition amount of HA are gained at positive voltage of 250V, frequency of 200HZ, deposition time of 40 min, the adding amount of HA 2 g/L. Through NaOH alkali treatment, the conversion of Ca and P elements of ceramic coating which prepared by either micro-arc oxidation or micro-arc oxidation / electro-deposition to HA can be achieved, and processing time, alkali solution temperature and solution concentration are the main factors which influence the conversion effect of HA. The proper parameters of alkali treatment for the two types of coating are respectively: processing time 2 days, alkali solution temperature 70℃, alkali solution concentration 0.20 mol / L; processing time 6 days, alkali solution temperature 70℃, alkali solution concentration 0.10 mol / L.Taking the HA content of the coating as main index and surface morphology as reference, the effect of three processes of micro-arc oxidation / electro-deposition, micro-arc oxidation / alkali treatment, micro-arc oxidation / electro-deposition/alkali treatment is compared. The result shows that HA contents are highest in the ceramic coating processed through micro-arc oxidation / electro-deposition / alkali treatment, moreover the surface morphology is suitable for implant material.