In-vitro electrochemical and bioactivity evaluation of \SS316L\ reinforced hydroxyapatite functionally graded materials fabricated for biomedical implants
By Muhammad Akmal and Muhammad Asif Hussain and Haris Ikram and Tahir Sattar and Sarah Jameel and Ju Young Kim and Fazal Ahmad Khalid and Jung Won Kim
Published in Ceramics International
2016
Abstract
Three sets of \FGMs\ of stainless steel 316L (SS) reinforced with micro-, nano- and mixed (1:1 mass ratio) hydroxyapatite (HA) were fabricated by powder metallurgy route. The concentration of the \HA\ was varied from 0 to 20 wt% with the increment of 5 wt% in all sets to strengthen the discrete layers of FGMs. The sintered densities along the discrete layers of \FGMs\ continually decreased as a function of \HA\ content which enhanced the bioactivity of the \FGMs\ towards the end with high content of HA. All \FGMs\ experienced an excellent corrosion response in the 0.9% NaCl solution with high passivity. Heavy diffusion of chromium (Cr) form \SS\ to \HA\ made the matrix Cr deficient. The chromium depletion regions around the interface of \SS\ and \HA\ caused an active corrosion behavior of \FGMs\ in 0.1 M \HCl\ solution. \FGMs\ with micro-sized \HA\ demonstrated the better corrosion properties than that of other FGMs. After being immersed in the simulated body fluid (SBF) solution for 7 days, the apatite layer formed on the surface of \FGMs\ with micro-sized \HA\ had a mature spherical morphology and leaf like shape for the other two FGMs. The apatite morphology and gained weight results proved the highest bioactivity for micro-sized \HA\ reinforced FGMs.