Impact of Hydroxyapatite Powder Particle Size on Mechanical and Electrochemical Properties of Flame-Sprayed Coatings for Titanium Implants

Hydroxyapatite (HA) coatings on titanium substrates are widely investigated for biomedical applications due to their biocompatibility and osteoconductivity. This study explores the impact of HA powder particle size on the mechanical and electrochemical properties of flame-sprayed coatings. HA powders were synthesized via a wet chemistry method and characterized using x-ray diffraction, FTIR, and scanning electron microscopy. Flame spraying was employed to deposit HA coatings of varying particle sizes (0-37 µm, 37-63 µm, 63-104 µm, and 104-125 µm) onto titanium substrates. Mechanical properties such as surface roughness, adhesion strength, wear resistance, and Vickers hardness were evaluated, revealing that coatings with smaller particle sizes exhibited smoother surfaces, higher adhesion strengths, superior wear resistance, and greater hardness. Electrochemical properties were assessed through potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid, demonstrating that coatings with finer particle sizes displayed enhanced corrosion resistance compared to those with larger particles. Overall, this study underscores the critical role of HA powder particle size in optimizing the performance of flame-sprayed HA coatings for biomedical applications.