Effect of TiO₂ addition on surface microstructure and bioactivity of fluorapatite coatings deposited using Nd:YAG laser

Abstract

To study the effect of titania (TiO2) addition on the surface microstructure and bioactivity of fluorapatite coatings, fluorapatite was mixed with TiO2 in 1:0.5 (FA + 0.5TiO2), 1:0.8 (FA + 0.8TiO2), and 1:1 (FA + TiO2) ratios (wt%) and clad on Ti-6Al-4V substrates using an Nd:YAG laser system. The experimental results show that the penetration depth of the weld decreases with increasing TiO2 content. Moreover, the subgrain structure of the coating layer changes from a fine cellular-like structure to a cellular-dendrite-like structure as the amount of TiO2 increases. Consequently, as the proportion of TiO2 decreases (increase in fluorapatite content), the Ca/P ratio of the coating layer also decreases. The immersion of specimens into simulated body fluid resulted in the formation of individual apatite. With a lower Ca/P ratio before immersion, the growth of the apatite was faster and then the coating layer provided a better bioactivity. X-ray diffraction analysis results show that prior to simulated body fluid immersion, the coating layer in all three specimens was composed mainly of fluorapatite, CaTiO3, and Al2O3 phases. Following simulated body fluid immersion, a peak corresponding to hydroxycarbonated apatite appeared after 2 days in the FA + 0.5TiO2 and FA + 0.8TiO2 specimens and after 7 days in the FA + TiO2 specimen. Overall, the results show that although the bioactivity of the coating layer tended to decrease with increasing TiO2 content, in accordance with the above-mentioned ratios, the bioactivity of all three specimens remained generally good.

Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

“…5, some ions still remain within the CL. It is noted, however, that some of the P ions produced in the FA decomposition process simply vaporize in the high-temperature cladding process [21,22]. Observing the results presented in Fig.…”

“…Many studies have shown that laser cladding enhances the bonding strength between bioceramic materials such as HA and FA and metallic substrates and hence inhibits the disintegration and detachment of the coating layer [21][22][23][24][25]. In a previous study [22], the present group investigated the effects of TiO 2 addition on the surface microstructure and bioactivity of FA coatings deposited on Ti6Al4V substrates using an Nd:YAG laser.…”

“…In a previous study [22], the present group investigated the effects of TiO 2 addition on the surface microstructure and bioactivity of FA coatings deposited on Ti6Al4V substrates using an Nd:YAG laser. In the present study, an investigation is performed into the bonding interface, phase composition and bioactivity properties of Al 2 O 3 -reinforced FA coatings deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process with a constant laser power/travel speed (P/V) ratio of 2:1 and three different settings of the laser power and travel speed, namely 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min.…”

Effects of Laser Power Level on Microstructural Properties and Phase Composition of Laser-Clad Fluorapatite/Zirconia Composite Coatings on Ti6Al4V Substrates

“…Nonetheless, as shown in Figure 9, some ions still remain within the CL. It is noted, however, that some of the P ions produced in the FA decomposition process simply vaporize in the high-temperature cladding process [37,38,39,40]. Observing the results presented in Figure 9, it is seen that the distributions of Zr in the CL and TL, respectively, are roughly the same.…”

“…Consequently, the present study investigates the microstructural properties and phase composition of composite FA coatings containing 20 wt % yttria (3 mol %) stabilized zirconia (ZrO 2 , 3Y-TZP) deposited on Ti6Al4V substrates using a laser-cladding technique. As in previous studies by the present group [38,39,40], the laser cladding process is performed using an Nd:YAG laser system.…”