Hydroxyapatite coatings by pulsed ultrasonic spray pyrolysis

Hydroxyapatite coatings on 316L stainless steel substrates were prepared using ultrasonic spray deposition with substrate temperature kept at 300 °C. Two spray patterns, continuous and pulsed (intermittent), were used coupled with precisely control of substrate movement. It was determined that the ability to form continuous and relatively dense, well bonded coatings, was related primarily to the control of the flowrate of precursor solution and temperature and movement of the substrate. The microstructure and bonding strength of the coatings were evaluated in relationship with continuous and pulsed (intermittent) spray routes. Coatings prepared by continuous spray contained relatively large cracks while coatings by pulse spray exhibited finer cracks and higher bonding strength.