Comparison between shot peening and abrasive blasting processes as deposition methods for hydroxyapatite coatings onto a titanium alloy

In this study, a flow of hydroxyapatite (HA) is combined with either a shot peening or an abrasive blasting processes and comparative testing has been undertaken to determine which technique yields increased coating coverage and adhesion onto a titanium alloy substrate. Both processes were shown to effectively deposit a layer of crystalline HA onto the titanium substrates at a number of air pressures and blasting heights. It was observed for both processes that an increase in particle kinetic energy produced corresponding enhancements in both deposition rate and surface roughness. The surface morphology obtained using the two treatments was significantly different with an increase in the average roughness (Ra) of ≈ 75% for samples treated with abrasive particles over shot peen particles. The shot peening process however produced a smoother layer of laminar apatite, which was readily removed from the surface using a scratch adhesion test technique. In contrast the combination of a jet of HA and abrasive powders resulted in an increase in surface abrasion and increased interlocking of the HA into the metal surface was observed. The resulting mechanical and chemical bonding resulted in enhanced HA adhesion.