生体用コバルト-クロム合金の微細組織に及ぼす元素添加の影響
Introduction |
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Cobalt base superalloys were originally developed for use in the gas turbine industry. However, mainly because of the recent advances in medicine and surgical technique, the biomedical applications as implant materials have now become the main usages of the Co-Cr-Mo (CCM) alloys, due to their excellent biocompatibility, mechanical properties, corrosion and wear resistance. For example, CCM casting alloy has been used in the femur component of artificial knee joint. A wrought CCM alloy has been used for hip heads, hip stems, metal-on metal hip joint bearings and knee stems. It is estimate that over 50% of the total hip replacement devices implanted thus far are cast CCM alloys. However, in the as cast condition Co alloy exhibit a relatively high frequency of failure owing to their apparent brittleness. Further improvements have lead to adoption in the medical field of wrought CCM alloys with ultra high strength and improved fatique and wear properties. In addition, the mechanical strength of these alloys can be enhanced further by heat treating without detrimental effect to their corrosion resitance. |
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Research Briefs |
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In the present work, the effect of alloying elements, heat treating process on microstructure and mechanical properties of biomedical CCM alloy during heat treatment process will be examined. It is therefore necessary to examine the effects of heat treatments and hot forging on the microstructure and the mechanical properties of CCM alloy. The main objectives of this experiment are to investigate the effect of Si, Mn, Si and Mn, Mg on microstructure (the formation of carbides and intermetalic phases) of CCM alloy and analyze the possibility of the mechanical properties improvement by controlling the phases and the precipitates in the CCM a lloy with Si, Mn and Mg addition. In this study, to obtain basic data to develop a new forging process, will be examined how pre-heating, aging and hot forging affect the microstructure and mechanical properties of CCM alloy. Electroytic etching with a sulphuric acid solution will be used to reveal the microstructure. Microstructure changes were analyzed by optical microscopy, SEM/EDX, X-ray diffraction analysis and transmission electron microscopy. The precipitates particles will be analyzed using transmission electron microscope with electrical extraction. |
 X-ray showing cast hip replacement in position [CDI, 2006] |
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 Microctructure of as-cast alloys Co-28Cr-6Mo-0.25C-1Mg |
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