Plasma sprayed nano-hydroxyapatite coatings on titanium alloys

Titanium alloys due to have excellent mechanical and biological properties can be a good replacement for bone tissues. However, lack of appropriate bonding between bone and titanium implant leads to separation from the bone. Also hydroxyapatite can be the best material for bone replacing due to chemical and structural similarity to mineral part of bone and good biocompatibility. One cannot use them in load-bearing sites such as bone and teeth due to poor mechanical properties. So the best way for producing biomedical implants is taking advantages of good mechanical properties of titanium implants and biological properties of hydroxyapatite. Therefore hydroxyapatite particles will be coated on titanium or its alloy substrates. In this study hydroxyapatite powder particles coated on titanium alloy substrate. Plasma sprays coating method due to its good properties, easy operation and low cost, will be used in commercial hydroxyapatite coating on the substrate implant. The problems of hydroxyapatite coating using this method are: formation of other calcium phosphate phases, poor adhesion of the coating and the substrate¡ formation of micro-cracks in the coating due to residual stresses caused by the high temperature process. To this end, hydroxyapatite has been coated on pre-heated titanium alloy in order to improving hydroxyapatite properties. Results indicate that residual stresses decreases in interface and adhesion improved by pre heating substrate.