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Cobalt-chromium alloys are commonly used for surgical implants because of their high strength, superior corrosion resistance, non-magnetic behavior, and biocompatibility. Cobalt-Chromium-Molybdenum (Co-Cr-Mo) applications include prosthetic replacements of hips. This paper presents the attempt to produce metallic implant using Co-Cr-Mo powder by MIM process, focusing on the effects of different heating rate during sintering process at 1380°C. Co-Cr-Mo powder were mixed homogeneously with palm oil and conventional binders respectively with powder loading 65 vol% and was injection molded using vertical injection molding machine with the nozzle temperature of 160°C to produce green compacts. The binders then was removed by solvent extraction process and sintered in vacuum condition at atmosphere 10-5 mbar at temperature 1380 °C with varied heating rate; 0.5°C/min, 1.0°C/min and 3.0°C/min . Results indicated that sintered density and tensile strength varied from 8.100 gcm-3 to 8.200 gcm-3 and 546.971 MPa to 798.767 MPa respectively. The mechanical properties comply with the international standard (ASTM F75).

Tendency of injection moulded parts to necessitate a long debinding time which consequently leads to an increase of defects formation has been a major obstacle for the economic process of Metal Injection Moulding (MIM). In the present study, a novel binder system based on waste rubber has been formulated in injection moulding of Molybdenum High Speed Steel (M2 HSS). The feedstock consisted of M2 HSS powder with mean diameter particle size of 16μm and binder which comprised of palm stearin, polyethylene, waste rubber and stearic acid. The moulded part was immersed into n-heptane at 60°C in order to remove the palm stearin and stearic acid, followed by sintering in a controlled vacuum atmosphere. Results showed that solvent extraction debinding technique allowed complete removal of palm stearin and stearic acid from the injection moulded part within 3 hours without swelling or distortion of the debound part. In addition, this study has demonstrated that, the novel binder system has successfully shorten the debinding time through a single stage debinding process whilst the sintered part possessed approximate density of 8.1 g/cm3 and hardness of 76.9 HRC.

Two starch/wax based binders were formulated for metal injection moulding of 316L stainless steel. The formulations difffer in term of the starch type which substitute the backbone polyethelene. Feedstock having powder loading of the stainless steel powder up to 65 vol.% can be injection moulded successfully. Solvent debinding was performed in water at a temperature of 60°C for 3 hours and followed by immersion n-heptane for duration of 2 hours to remove the residual wax. The remaining binder was thermally extracted at 4500 with heating rate of 3°C/min, with no defects. The parts were then sintered in vacuum atmosphere within a temperature range of 1300°C to 1380°C. Approximately, 6.8 g/cm3theoretical density, hardness of 188.8 HV and tensile strength of 229.3 MPawere achieved for cassava starch/wax based binder while rice starch/wax based binder possessed 8.6g/cm3theoretical density, hardness of 385 HV and tensile strength of 462.1 MPa.