This paper reports on the effect of sintering temperature on the density, hardness and strength of Co30Cr6Mo fabricated by Metal Injection Molding (MIM). Palm stearin and polyethylene have been used as the binder system. The feedstock was injected by injection molding machine to produced micro dumbbell shape part. The specimens were solvent debound in n-hepthane for 15 minutes and thermally debound in argon atmosphere for an hour. The sintering was carried out in vacuum furnace at temperature 1250 °C, 1300 °C and 1350 °C for an hour. The density, hardness and tensile strength were then measured. The specimens that have been sintered at 1350 °C showed highest density and tensile strength compared with samples sintered at 1250 °C and 1300 °C. The samples which has been sintered at 1350 °C has highest relative density (93 %), compared with the same sample sintered at 1250 °C (87 %) and 1300 °C (76 %). As the temperature increased, the tensile strength increased gradually 400 MPa to 700 MPa and the micro hardness also increased from 200 Hv to 540 Hv. The morphology of sintered specimen showed that the morphological bonding between powder particles becomes denser at highest sintering temperature of 1350 °C.
Powder injection molding (PIM) is among the most known forming techniques that use material powders. This technique has been widely evaluated for the production of large scale and small components using metal and ceramic powders. Nano particles have larger surface-to-volume ratio compared with large-sized particles, thus they display high surface area. Some merits in the application of nano-sized particles in the PIM process includes increasing its comparative density at a low sintering temperature, decreasing sintering temperature, decreasing grain size of sintered bodies, increasing hardness value, and improving surface properties. However, it also has several disadvantages, which include increasing the viscosity behaviour of feedstock, oxidation, and agglomeration. This article reviews current studies on the effects of nano-sized particles on the PIM process and finding solutions to address its disadvantages.
This research studies the effect of injection moulding parameters on the density of green body of Cobalt-30Chromium-6Molybdenum (Co-30Cr-6Mo) for powder injection moulding (PIM) feedstock. In this paper 20 micron Co-Cr-Mo powder was mixed with a palm stearin and polyethylene binder system. L18 orthogonal array by Taguchi Method was used to optimize and predict the future performance. Several injection parameters were optimized such as injection temperature, holding pressure, injection temperature, and mould temperature and injection time. The result shows that the optimum combination of these parameters will produce higher density micro parts. The optimum parameters for 67% powder loading of 20µm Co-30Cr-6Mo powder is 180oC injection temperature, while injection pressure, mold temperature, packing time and injection time are 10 bar, 100oC, 5 s and 7 s respectively.
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