Effect of acid passivation and H2 sputtering pretreatments on the adhesive strength of sol–gel derived Hydroxyapatite coating on titanium surface

Abstract

In this study, in order to increase the adhesive strength of a Hydroxyapatite (HA) coating, deposited on the surface of commercially pure titanium, acid passivation and hydrogen sputtering pretreatments were used. The pure titanium surfaces were passivized by acid solution and treated by hydrogen sputtering, at a temperature of 300 °C for 1 h. Ca(NO3)2·4H2O and NH4H2PO4 were chosen as starting precursors for Ca and P sources. HA coatings on the titanium surface were deposited using the sol–gel method and sintered in air at the temperatures of 750oC-900 °C for 1 h. XRD, SEM, EDS and AFM analysis techniques were used for structural and morphological characterization. Scratch test was performed for determining the adhesion of HA coatings. The experimental results indicated that compact and crack free HA coating, which has a Ca/P ratio of 1:6, was formed on pure Titanium (Ti) surface. The adhesive strength values of the HA coating, pretreated with H2 sputtering and acid passivation were found to be 72.84 MPa and 55.83 MPa at temperature of 900 °C, respectively. It was observed that H2 plasma sputtering pretreatment, improved the adhesive strength of the HA coatings compared to pretreatment with acid passivation.