An Investigation into the Surface Finish of Laterally Face Milled Cobalt-chromium-molybdenum Alloys
Lees, Sam Brian
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The surface finish of multiple machined dental alloy specimens has been analysed, evaluated and compared. The dental alloy used in this investigation was cobalt-chromium-molybdenum (CoCrMo). CoCrMo is a popular biomedical material commonly found in artificial joints and dental implants. Lateral side milling was used to machine the specimens while four different cemented tungsten carbide (WC) mills were used at varying rotational spindle speeds to provide a comprehensive look into how different configurations would affect the surface quality of this alloy. In dental applications a high quality surface finish of the implant is crucial to minimize plaque and food build up and therefore an in-depth investigation into the link between machining specifications and surface finish was needed. Cutting forces of each experiment were supplied with the milled specimens. Scanning electron microscopy of each specimen and mill in this study was then undertaken. Furthermore, micro hardness testing, and roughness testing were undertaken on the dental alloys to create a comprehensive results profile. It was observed that in general, roughness increased with increasing spindle speed, though multiple data sets were incomplete. Obtained cutting forces were shown to vary for each mill and spindle speed. The primary observation from this study was that surfaces that appeared to be smooth were microscopically rough with chip rewelding, mill vibrations, mill wear, and the minimum chip thickness mechanism dictating the extent of the surface roughness. Finally, a DLC mill coating was found to be not suitable for milling CoCrMo.