CaP coating of porous sintered Ti6Al4V powder compacts using biomimetic and sol-gel methods

Abstract

In this study, two methods of CaP coating, dip coating and biomimetic, on porous Ti6Al4V powder compacts to be used in novel spinal cages were experimentally investigated. The powder compacts produced by sintering of compacted green powders contained 37% open porosity with an average pore size of 63 micrometers. Dip-coating solutions were prepared using sol-derived and commercially available HA powders.Biomimetic CaP coatings were performed in 1(at 37°C, Ph . 7.4) °, 5 (at 37°C, pH .6.0) and 10x (at room temperature, pH . 5.8) simulated body fluid (SBF).The porous Ti6Al4V powder compacts were successfully coated using HA dip coating solutions. The optimum soaking times were 3 and 1-minute for sol-derived and milled and unmilled comercial HA powders, respectively. Increasing soaking times further started to fill the originally open pores. The thicker deposit and cracks were observed at the sintering necks of the particles was believed to be due to capillary effects drawing the coating solution into this concave region. Milling of HA powder induced more homogenous coating layer on the Ti6Al4V particles.Increasing Ca and P concentrations in SBF increased the rate of CaP nucleation.Alkaline (NaOH) and heat-treatment (600oC for 1 hour) further accelerated CaP formation. The complete coating of treated and untreated compacts was 14 and 21 days using 1xSBF, 24 and 36 hours using 5xSBF and 4 and 6 hours using 10xSBF, respectively. When considered crack free and homegenous coating layer, dip coating using milled commercial HA powder was found to be the most appropriate method for the coating present powder compacts.