Influences of heating condition and substrate-surface roughness on the characteristics of sol-gel-derived hydroxyapatite coatings

A prepared transparent HA solution was coated on Ti6Al4V substrates by a spin-coating technique. The crystallization of the sol-gel-derived HA coated on the metallic substrates could be done at relatively low firing temperatures (as low as 600 degreesC). The characteristics of the HA-coated layer were dependent on the surface roughness of substrates and heating conditions such as firing temperature, holding time, heating rate, and atmosphere. The heat treatment at a slow heating rate (<2 degreesC/min.) and a long heating time (> 10 hrs) at 600 degreesC in air produced the uniform surface and improved the crystallinity. The HA layer coated on 20 mum grit-blasted substates was more uniform and had fever cracks after firing, compared with that coated on 100 mum grit-blasted rougher substrates.