The effect of sintering temperature to the quality of hydroxyapatite coating on cobalt alloys as the candidate of bone implant prosthesis

Total hip replacement (THR) that is widely used today is the cemented type, which its application will lead to aseptic loosening. To avoid the occurrence of aseptic loosening, THR coated with hydroxyapatite (HA) is required because HA is osteoconductive which can stimulate the growth of osteoblasts. This study aims to determine the optimum sinter temperature which produce HA coating suitable as implant material. To achieve these objectives, the electrophoretic deposition (EPD) conducted coating method at concentrations of HA 1, 0M, voltage of 100V for 30 minutes and then sintered at temperatures are 550°C, 700°C and 900°C respectively detention for 10 minutes. The results showed that the treatment of sintering after the coating process through the EPD method affect the characteristics of the layer thus formed. Sintering process affects the crystallinity of the HA layer. The higher the sintering temperature the higher its crystallinity. The higher the crystallinity the stronger the HA layer attached to the substrate cobalt alloy. Based on this research, the selected sintering temperature was 900 °C for 10 minutes which produced a layer of HA with the best characteristics that meet the standard of implant prosthesis, the crystallinity of 89.4%, thick layer of 70.80 ± 4.18 μm, adhesion strength of 21.87 ± 0.23 MPa, the corrosion rate of 0.025 mpy and 70.3% cell viability.