Production of plasma electrolytic oxide coatings on Ti6Al4V alloy in aluminate-based electrolytes

Titanium alloys have been adopted as standard materials in aviation, biomedical and chemical industries owing to their outstanding properties involving high-specific strength, high corrosion resistance and biocompatibility. But, an important shortcoming related to the application of titanium alloys is their poor wear resistance. When titanium slides against itself or other metals it tends to gall and cause adhesive wear damage. In this study, oxide coatings were produced on Ti6Al4V using plasma electrolytic oxidation technique. Different electrolyte compositions were formulated to develop hard coating with less porosity and high load bearing capacity. The nano-indentation test was carried out to determine the micromechanical properties of the coatings. The scratch test was utilised to determine the adhesion strength of coatings. Dry sliding wear tests were performed against alumina ball. Test results showed that tungstate additive increased the wear resistance of plasma electrolytic oxidation coating while the addition of pyrophosphate reduces its wear resistance.