Metal injection moulding of hip stem CoCrMo alloy powder using palm stearin binder system

Metal Injection Moulding (MIM) has undergone development of various binder systems with the aims of shortening the overall debinding time duration. In the present work, binder system based on biopolymer has been utilised in injection moulding of hip stem CoCrMo alloy powder. The feedstock consisted of CoCrMo powder with mean diameter particle size of 16 μm and binder which comprised of major fraction of wax and minor fraction of polyethylene. The moulded part was immersed into n-heptane at 60 °C in order to remove the palm stearin, followed by sintering in a controlled vacuum atmosphere. Results showed that solvent extraction debinding technique allowed complete removal of palm stearin from the injection moulded part within 5 hours without swelling or distortion of the debound part. Lower heating rate is needed during thermal pyrolysis in order to retain the shape due to the thickness of the part

Physical and mechanical properties of injection molded co-cr-mo alloy powder for orthopedic applications

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 oC. Co-Cr-Mo powder was mixed homogeneously with palm oil based binder with powder loading of 65 vol% and was injection molded using vertical injection molding machine with the nozzle temperature of 160 °C to produce green compacts. The binders were then removed by solvent extraction process and sintered in vacuum condition at 10-5 mbar at 1380 °C. Results indicated that sintered density and tensile strength varies from 8.1 g/cm3 to 8.2 g/cm3 and 546 MPa to 797 MPa respectively. The mechanical properties comply with the international standard (ASTM F75)