Applying and Characterization of Physical - Chemical Properties of HA and TiO2 Coatings on Ti-6Al-4V Alloy
In current research, single HA, single TiO2, and double layer HA/TiO2 coatings was applied on Ti-6Al-4V substrate by AC/DC magnetron sputtering method with obtained optimum parameters. The parameters were: power 175 W to coat single HA layer, optimum Ar/O2 ratio of 30/70 for coating TiO2 thin film, both which applied for HA/TiO2 multilayer coating sample. In addition, the effect of heat treatment temperature on hydroxyapatite layer growth was investigated. Phase formation, morphology, and roughness of coatings surface were investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Force Microscope (AFM), respectively. Also, the effect of exposing samples to simulated body fluid (SBF) was studied. SEM images confirmed the formation of calcium phosphate precipitations on the surface of coatings. The XRD patterns and EDS analysis results showed the precipitations formed on surface of coatings were calcium phosphate phases. The corrosion test showed that the corrosion resistance of heat-treated HA/TiO2 multilayer coating was improved, 0.041 A.cm-2 in comparison with 0.015, 0.007, and 0.003 for single HA, untreated multilayer, heat-treated multilayer at 500ºC and 800ºC, respectively. SEM micrographs showed that at same periods of soaking samples into SBF, more precipitation formed on HA/TiO2 coating in than HA coating which indicates the improvement of bioactivity of Ti implants with applying the HA coatings, also showing 300 nm thick layers of HA and TiO2 on the alloy surface. AFM results showed that surface roughness of uncoated Ti alloy was improved by applying coatings of single HA, single TiO2, and multilayer HA/TiO2. The results of AFM also demonstrates that the single HA and single TiO2 coatings had similar surface roughness ( 64 Å) while untreated multilayer coating had an improved roughness of 73.5Å. The surface roughness was increased drastically for heat-treated multilayer sample at 800ºC due to positive effect of heat treatment on hydroxyapatite coatings surface properties.
Iranian Journal of Ceramic Science & Engineering, Volume:6 Issue:1, 2017
9 - 25
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