January 25, 2019

Influence Of HVOF Parameters On Hap Coating Generation: An Integrated Approach Using Process Maps

The first-of-its-kind use of the active learning (AL) framework in thermal spray is adapted to enhance the prediction accuracy of the in-flight particle characteristics. The successful AL framework implementation via Bayesian Optimisation is beneficial in, first, reducing the An experimental approach based on design of experiments, process maps and the analysis of deposition first stages to improve the biocompatibility of High-Velocity Oxygen Fuel (HVOF) hydroxyapatite (HAp) coatings is here presented. A two-level design of three factors (23) was performed using the stand-off distance (SOD), the fuel‑oxygen ratio (F/O) and the powder feed rate (PFR). The effect of these experimental factors on the first stages of the coating formation was investigated to study the physical state of the particles before and after impacting the substrate. This study allowed the selection of the most suitable deposition parameter combinations to obtain HAp coatings with optimal crystallinity (>45%), Ca/P ratio (approx. 1.67), phase content (>95% of HAp), which guarantee the coatings mechanical stability and biocompatibility. The behavior of the coating within simulated body fluid (SBF) and cell culture (hFOB) was studied to analyze the apatite layer formation and the extracts cytotoxicity on human osteoblasts, respectively. The results show that the F/O ratio is the most influential factor on temperature and velocity on the in-flight particles and therefore on the coating properties. The SBF results confirmed the formation of an apatite layer after 14 days of immersion. Finally, the mitochondrial activity, measured by the MTS assay, and cell membrane integrity measured by LDH liberation assays, show that the coating released material does not induce toxicity on the exposed cells.

Link to publication

Originally published at Surface and Coatings Technology (volume 358, 25 January 2019, Pages 299-307)

By J.A. Hermann-Muñoz, J.A. Rincón-López, G.A. Clavijo-Mejía, A.L. Giraldo-Betancur, J.M. Alvarado-Orozco, A. De Vizcaya-Ruiz, J. Muñoz-Saldaña

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