Cold spray deposition of hybrid composite coating on magnesium for implant application
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Date
2016-06
Authors
Tang, Chin Wui
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Abstract
Magnesium is a light weight material which makes it prospective to become a suitable replacement to denser metal such as steel, titanium and aluminium in orthopaedic implant application. However major drawback is its high and localised corrosion rate in biological environment, and it would fail prematurely due to its poor mechanical integrity. Hence, an osteoconductive approach is adopted to apply hydroxylapatite-alumina (HAPAl2O3) hybrid composite coating on the Mg substrate via Cold Spray Technique. The percentage of alumina in the HAP-Al2O3 hybrid composite towards its bioactivity and mechanical properties (hardness and coating strength) is studied. Its bioactivity and corrosion behaviour of the HAP-Al2O3 hybrid composite coating is also investigated in in vitro biological environment. The result showed successful deposition of Al2O3 which forms HAP-Al2O3 hybrid composite coating. The sample composition with the highest coating thickness is sample HAP-10 wt%Al2O3, with coating thickness of 38.12 ± 2.58 μm. The increasing percentage of Al2O3 in the sample showed a decreasing thickness in the hybrid composite coating. The Vickers microhardness value of the hybrid composite coating increases with increasing Al2O3 weight percentage in the coating. Meanwhile, the coating bond strength decreases with increasing Al2O3 weight percentage in the coating. Sample HAP-10 wt%Al2O3 has the highest coating bond strength, of 12 ± 0.50 MPa. For the in vitro SBF immersion test, sample HAP-10 wt%Al2O3 showed a good bioactivity due to the formation of calcium-deficient hydroxyapatite (CDHAP).