Development of Bio-implant materials by Plasma-Spray Coating of Apatite and Their Evaluation

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In order to fabricate substitute artificial bone materials, the author tried plasma-coating of hydroapatite layer on metallic materials. However, the plasma-sprayed layers are so porous that body liquid penetrates to the substrates and attacks them. Moreover, because of extremely high temperature of ca.2,000℃, hydroapatite layer may easily decomposes and lose contact to the substrates. The author solved these problems and developed the plasma-sprayed hydroapatite coating materials. (1)The reaction of H3PO4 and Ca(OH)2 could not give hydroapatile but aging and heat-treatment promoted change into hydroapatite. (2)Plasma-spraying of, hydroapatite formed the coating layer without hydroapatite. However, controlling of the powder radius improved formation of hydroapatite. (3)Plasma-sprayed hydroapatite was amorphous, but crystallized by 3 hour and 800℃ heat-treatment. (4)Corrosion test of the hydroapatite-coated pure titanium, commercial Ti rod and SUS316 stainless steel was performed in 3.5%NaCl solution. Only the pure titanium was improved by hydroapatite coating. This is probably because joint between the hydroapatite layer and the substrate was tight. It was also found that the heat diffusion treatment improved their jointing.