Bioceramics coating on Ti–6Al–4V alloy by microwave processing

Abstract

A novel method of hydroxyapatite (HA) coating on Ti–6Al–4V alloy by microwave (MW) processing has been developed to form an adherent coating within ∼25 min. The X-ray diffraction pattern of the coated sample shows the presence of HA and titanium oxides. Scanning electron micrograph indicates that the thickness of the coating is to be ∼150 μm with a good interface with the alloy. The compositional analysis using energy dispersive X-ray spectroscopy also confirms the formation of a composite coating of apatite and titanium oxides. The MW active nature of the non-stoichiometric titanium oxides seems to influence the bonding of HA with the titanium oxide grown on the alloy surface. The presence of the Widmanstätten structure of the substrate as observed by optical microscopy indicates that the process temperature of the coating may be above β transus temperature of the alloy. The alloy substrate also shows an increase in the hardness and Young's modulus which may be due to diffusion of oxygen and/or nitrogen during the coating process into the alloy.