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1602 |
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Nanomechanical assessment of commercially produced plasma sprayed hydroxyapatite coatings |
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Karlis Gross / Uni of Melbourne, Australia S. Saber-Samandari / Dept of Mechanical and Manufacturing Engineering, Uni of Melbourne, VIC 3010, , Australia K.S. Heemann/ Dept of Mechanical and Manufacturing Engineering, Uni of Melbourne, VIC 3010, , Australia |
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Hydroxyapatite coatings are used on orthopaedic prostheses to provide improvements such as faster bone growth and strong bonding to the surrounding bone. The standards allow a wide range of coatings to be applied on implants with requirements only for the coating structure, chemistry and bond strength. Further improvements of these coatings needs the use of micro and nanocharacterization techniques. Nanoindentation has not been applied to any great extent on thermally sprayed coatings, and offers potential for revealing the micromechanical properties of splats and the entire coating. Hydroxyapatite coatings from four different implants were cross-sectioned, polished and nanoindented using a Berkovic indentor to determine the properties of different areas within the coating. New data has been made available on the mechanical properties (hardness and elastic modulus) of the amorphous and crystalline areas. The amorphous phase has revealed a hardness of 2 compared to 4 for the crystalline portions formed during coating formation. Reference to powder feedstock reveals that a wide range in mechanical properties can be set at the powder stage and the inclusion of such partially melted powders can provide an elastic modulus match between the different microstructural components within the coating. Furthermore, the control of powder microstructure and coating crystallinity provide a good means of matching the modulus to the surrounding bone for good implant stabilization. |