Tribocorrosion Behavior Study Of Micro-arc Oxidation Coatings On Ti6Al4V Alloys

Ti6Al4V alloys are widely used in aerospace,marine and biomedical applications due to their good mechanical properties,corrosion resistance and biocompatibility.However,in the application of marine detectors and biomedical human implants,they are susceptible to the effects of looth wear and corrosion(ie,tribocorrosion).Thus,modification process should be carried out to their surface.In this paper,micro-arc oxidation(MAO)was utilized to the surface modification of Ti6Al4V alloys.In addition,the tribocorrosion behavior of MAO coatings prepared in silicate electrolyte system with graphene oxide(GO)additive and MAO coatings containing Ca and P elements with various voltages were respectively studied.In the study of adding GO into silicate electrolyte system,it was confirmed that the MAO coatings were consisted of rutile and anatase TiO2 and the relative content of rutile TiO2 increased with the increase of GO amount.Besides,the corrosion behavior of the MAO coatings prepared in the silicate electrolye system was dominated by the diffusion process of corrosive ions in 3.5%NaCl aqueous solution.Thus,the utilizing of GO additive promoted the GO particles inserting into the MAO coatings and the existing of GO particles in MAO coatings inhibited the penetration of corrosive ions from coating to substrate,thus promoting the elevation of corrosion resistance of MAO coatings.In addition,according to results related to tribocorrosion,it can be determined that GO addictive in these MAO processes improved the tribocorrosion resistance of MAO coatings.Due to the low coefficient of friction,high open circuit potential and the lowest wear volume,the MAO coating with 10 mL/L GO performed the best tribocorrosion resistance among these samples.In the study of effect of various voltages on MAO coatings conataing Ca and P elements,it was found that the MAO coatings were consisted of outter porous layer and inner barrier layer.The thickness and corrosion resistance of MAO coatings increased as the voltage increased from 380 V to 400 V.However,as the voltage varied from 400 V to 420 V,there was not significant variation for the thickness of MAO coatings and the corrosion resistance declined.Besides,it can be found that the hardness of coating increased with the increase of applied voltage.After the analysis of tribocorrosion behavior of MAO coatings,it can be found that the open circuit potentials of samples with 380 V and 420 V didn’t varied significantly,thus the tribocorrosion behaviors were tended to the wear processes.The tribocorrosion behavior of sample with 400 V can be described as the micro-cracks produced by wear process inducing the decline of corrosion resistance,which leading to the more wear effect.This phenomenon was also called as synergistic effect of wear and corrosion.