HYDROXYAPATITE/TRICALCIUM PHOSPHATE BI-LAYERED COATINGS ON MAGNESIUM ALLOY AZ31: STUDY OF CORROSION RESISTANCE AND BIOMINERALIZATION

• Main Author: Oki Firmansyah, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53640
• Institution: Institut Teknologi Bandung

Magnesium Alloys (Mg) have biodegradable ability and clinically proven as a low load-bearing implant. Also, bone-like mechanical properties of Mg alloys may avoid the stress-shielding phenomenon. The biggest challenge of Mg alloys as an implant is fast corrosion rate in the physiological environment. In order to increase the corrosion resistance, several methods such as purification, alloying, surface treatment, and coating deposition have been used. Corrosion resistance of Mg alloy could be improved using Calcium phosphate (CaP) material like hydroxyapatite (HAp) as a coating layer both in vivo and in vitro trial. However, HAp has poor bioactivity and osteoconductivity due to lower dissolution rate. Beta-tricalcium phosphate (?-TCP) has faster dissolution rate than HAp, which may speedup bone healing. In this study, HAp and ?-TCP bi-layered coating were used to coat Mg alloy (AZ31). HAp is applied as first stable layer to increase the corrosion resistance of Mg. At the same time, ?-TCP is used as the second or outermost layer to improve bioactivity. This research aims to improve Mg corrosion resistance, evaluate biodegradation, and biomineralization behaviour of HAp/TCP bi-layered coating on AZ31 alloy. The High-Velocity Oxygen-Fuel spraying (HVOF) method is carried out to obtain bi-layered coating with an excellent layer structure, low porosity, high density, and high adhesion strength. As the results of this study, bilayered coatings were formed with high density and crystallinity. Potentiodynamic polarization test showed corrosion resistance improvement with Ecorr and Icorr values to -1.312 V and 30.25 ?A/cm2, which is better than other single-layered HAp coating on Mg alloys. Immersion test in SBF solution revealed that bone-like apatite formation on the coating. The apatite layers formation indicates excellent mineralization of Mg substrate due to the presence of HAp/TCP bi-layered coating. This study shows that HAp/TCP bi-layered coatings could improve corrosion resistance and mineralization of Mg alloy as an implant material with promising advanced biodegradation ability.