Electrodeposition of Hydroxyapatite Coating on Ti6Al4V Alloy: Mechanistic Investigation of the Substrate Crystallographic Texture Effect

Abstract

Hydroxyapatite (HAp) coating electrodeposition was performed on three orthogonal surfaces of duplex-annealed Ti6Al4V alloy. This approach made it possible to investigate the effect of substrate crystallographic texture on hydroxyapatite coating properties exclusively from its microstructure. The coating characteristics were evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, laser surface profilometry, and potentiodynamic polarization test. The results showed that the presence of ("10" "1" ̅"0" ) low-surface energy planes leads to the smaller HAp deposits of 39±4 µm due to the higher nucleation rate during electrodeposition. The highest surface roughness value of 75±1 µm, as well as the lowest degree of crystallinity, equal to 23.5%, belonged to the surface in which ("0001" ) and (112 ̅0) planes of high-surface energy placed in parallel to the surface. The electrochemical test results showed that the protective efficiency of HAp coatings was the highest for the surface with ("10" "1" ̅"0" ) planes in parallel. This was attributed to the increased thickness and the low porosity content of the coating.