During plasma spraying, partial hydroxyapatite (HA) decomposes and partial constituent of the coatings transforms into amorphous phase, which greatly reduce the crystalline HA content of the coatings. Experimental results indicate that the content of crystalline HA in the coatings can be increased significantly by saturated steam treatment. Owing to the existence of steam, the reaction [3Ca3(PO4)2+CaO+H2O→Ca10(PO4)6(OH)2] will take place during treatment, and with the increase in processing temperature and the increase in holding period, the content of the crystalline HA increases obviously. In addition, HA nanocrystals can be obtained with suitable processing parameters.
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