Abstract: A hydroxyapatite/hydroxyfluorapatite (HA/FHA) double layer was coated on Al_2O_3 by a powder slurry method. Each layer(HA,FHA) was deposited on Al_2O_3 repeatedly to induce a uniform layer and the final heat treatment was carried out above 1300 ℃ to consolidate the coating layer. During this process, without the FHA-intermediate layer, a severe reaction between HA and Al_2O_3 occurred to form tri-calcium phosphate and calcium aluminates. SEM, XRD and bonding tests of the coatings were performed. The results showed that the FHA layer between the HA layer and the Al_2O_3 substrate was effective in suppressing the reaction between HA and Al_2O_3.The obtained HA/FHA double coating was micro-porous and relatively rough, but was firmly adhered to the Al_2O_3 substrate, having a bonding strength of approximately 30 MPa after heat treatment above 1300 ℃.

Key words: hydroxyapatite%hydroxyfluorapatite%coating%bonding strength%alumina