Preparation of Ceramic Composite Coatings on Ti-6Al-4V Alloy by Surface Nanocrystallization/Micro-Arc Oxidation

Abstract

Nanostructured surface layer was produced on the Ti-6Al-4V alloy by surface mechanical attrition treatment (SMAT) technique, and then the ceramic composite coatings of surface nanocrystallization/ micro-arc oxidation (SNC/MAO) were prepared on the nanocrystallized surface of Ti-6Al-4V alloy by pulsed single-polar micro-arc oxidation in NaAlO2 solution. The phase composition, morphology of surface and section and element content of the nanostructured surface layer and the ceramic coatings were investigated by XRD, TEM, SEM and EDS, respectively. The results showed that after the SMAT technique treatment for a short period of time, the surface layer was refined into ultrafine grains. The thickness of the coatings on the substrate treated by SMAT technique is about 10μm by micro-arc oxidation, which is thicker than the ones on the substrate untreated by SMAT technique, and the ceramic coatings are mainly composed of Al2TiO5. Besides, a bright interface layer comes out between the substrate and the coating when the substrate treated by SMAT technique. The influences of the SMAT technique on the surface morphology of the ceramic coatings also changed. The coatings using the SMAT technique were more compact and less porous than the ones on the substrate untreated by SMAT technique. The content of elements in the nanostructured surface layer on Ti-6Al-4V alloy had changed after the SMAT technique: the content of Ti increased, the content of V decreased, and the content of Al changed a little. The contents of Al and P in the coating increased while the content of Ti decreased.