Higher in-flight particle velocities enhance in vitro tribological behavior of plasma sprayed hydroxyapatite coatings

Hydroxyapatite (HA) coatings were deposited onto Ti6Al4V substrates via atmospheric plasma spraying under systematically varying spray parameters, leading to different in-flight particle velocities. Morphology, composition, and tribological properties of the coatings were then studied. The coatings deposited at higher in-flight particle velocities exhibited smoother surface topography, better inter-particle bonding and higher Young's modulus and hardness. Ball-on-disc tribological results showed that the friction and wear of the HA coatings significantly decreased with increased in-flight particle velocity under both dry and wet (Hanks' solution) conditions. All HA coatings exhibited lower friction and wear during the wet sliding due to the lubricating effect of the solution.