Effect of solid loading and dipping time on microstructure and shear strength of hydroxyapatite coatings deposited via dip coating technique

Abstract

Stainless steel (SS) 316L has been used in the biomedical field, especially as a bone plate. Although SS 316L provides high mechanical and corrosion resistance, the low biocompatibility of SS 316L hampers its application for permanent bone implants. This research investigates the effect of hydroxyapatite loading and dipping time on microstructure and shear strength of hydroxyapatite layer coated on SS 316L surface. Hydroxyapatite powder and aquadest were mixed with sago starch to form suspension with stirring rate at 150 rpm for 20 hours. Subsequently, the stainless steel plate was dipped into the suspension and put into the oven at 110°C for 10 minutes, followed by sintering at 800°C for 1 hour. The coating process was carried out with variations in the hydroxyapatite addition of 8, 10, and 12 grams and dipping time variations of 2, 6, and 10 seconds. Then, the microstructure of stainless steel coated hydroxyapatite was analyzed with X-ray diffraction, scanning electron microscopy, and autograph. The result shows that the increase in hydroxyapatite and the dipping time increase the hydroxyapatite layer on stainless steel. The hydroxyapatite with the thickest layer is 65 µm for 12 gr hydroxyapatite addition and dipping time of 10 seconds. Moreover, shear strength of the layer increase with hydroxyapatite addition and dipping time. The maximum shear strength obtained in this study is 244 kPa.