Papers by Keyword: MIM

Abstract: In this study to the authors knowledge 1^st time, Metal Injection Molding (MIM) technique was used to introduce the magnesium alloy WE43 into binder-based powder metallurgical (PM) processing. Towards later adoption to binder-based 3D-printing technologies, Fused Granular Fabrication (FGF) technique, respectively for biomedical application. Metal Injection Moulding (MIM) is a binder based economic near net shape prototyping technique for production of complex shaped parts in high number and high reproducibility, and hence perfect as a “gold standard” for the introduction of new Mg-alloys into binder passed PM processing. In doing so, dogbone shape tensile test specimen were manufactured by MIM, subsequently solvent debound and conventional sintered in argon atmosphere. Next to the as sintered specimens (asS), solid solution heat treatment (T4) and precipitation hardening heat treatment (T6) were performed on additional specimens. Tensile tests pointed out high strength and ductility of as sintered and heat treaded specimens of up to 226 MPa UTS at 7.6% elongation at fracture. The microstructure was investigated using SEM imaging technique equipped with energy disperse x-ray energy analysis (EDX) for secondary phase analysis. Hence, the magnesium alloy WE43 could be identified as a high strength and ductility alloy for binder based PM processing for future additive manufacturing approaches in biomedical applications of patient adapted implants.

Abstract: In recent years, metal injection molding (MIM) has been adopted as a process for manufacturing a solenoid valve which is a component of an electronic fuel injector, and PB permalloy components have been commercialized. However, Ni, an element of PB permalloy, is expensive material, making it difficult to produce the fuel injector component at a low cost. As a solution to this problem, we studied the magnetic and mechanical properties of Fe-Cr-Si alloys by MIM process. These results revealed that the magnetic and mechanical properties were improved by reducing Cr content. However, reducing Cr content is expected to reduce corrosion resistance of the alloys. In this study, Fe-Cr-Si-Mo alloy specimens containing Mo to improve corrosion resistance are manufactured by MIM process, and we investigated the magnetic and mechanical properties. These results revealed that Fe-10Cr-3Si-2Mo alloy is a material with an excellent balance between magnetic and mechanical properties.

Abstract: In recent years, metal injection molding (MIM) has been adopted as a process of manufacturing a solenoid valve which is a component of an electronic fuel injector, and PB permalloy component has been commercialized. However, Ni that is an element of PB permalloy is expensive material, and it makes difficult to produce the injector component in low cost. To reduce the production cost, we can use Fe-Cr alloys, although there are few studies on Fe-Cr alloys by MIM process. In this study, Fe-Cr-Si alloy specimens were manufactured by MIM process and the magnetic and mechanical properties were investigated. From these results, we found that high performance Fe-Cr-Si alloy can be obtained by setting Si content to 3% and reducing Cr content.

Abstract: Ti 6-4 and other Titanium alloys have great potential for Metal Injection Molding of high performance parts. Markets like Automotive, Aerospace, 3C and sporting goods can benefit from the low density and high strength of Titanium. A new feedstock has been developed that incorporates pre-alloyed Ti 6-4 and discrete additions that simplify MIM processing and enhance properties. Processing and sintering parameters are presented together with mechanical and metallurgical properties of completed parts.

Abstract: Feedstock preparation is one of the most crucial steps that will influence the metal injection molding process. In this study, the properties of Cu and space holder powder were determined. Powder morphology was captured using Scanning Electron Microscopy (SEM). Three different ratios of feedstocks were premixed with potassium carbonate as space holder using Turbulence Shaker mixer prior to mixing with constant binder system consist of waste rubber (WR). Mixes of three feedstocks with from 40, 50 and 60 wt. % were carried out in Brabender Plasticoder. All feedstocks were mixed at constant powder loading. The feedstocks were successfully injection molded using Vertical Injection Molding machine at 200°C.

Abstract: 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).

Abstract: 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 16μm and binder system 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 paraffin wax and stearic acid, followed by sintering in a controlled vacuum atmosphere. Results showed that solvent extraction debinding technique allowed complete removal of paraffin wax and stearic acid from the injection moulded part within 5 hours without swelling or distortion of the debound part. Lower heating rate needed during thermal pyrolysis in order to retain the shape due to the thickness of the part.Keywords: CoCrMo, MIM, wax, debinding,

Abstract: Controlled thermogravimetric pyrolysis of a metal injection moulding (MIM) feedstock was performed in order to characterize the associated thermal debinding processing in an inert atmosphere. The feedstock was formulated using Ti-6Al-4V metal powders and a newly developed MIM binder system. The catalytic effect of the metal powder on the decomposition of the binder components in the MIM feedstock is observed. The thermogravimetric analysis also reveals that thermal debinding is characterized by a multistage degradation behaviour of the binder system. In order to determine the kinetic parameters of the degradation step Ozawa and Ozawa-Flynn-Wall methods were applied. Activation energies with the degree of thermal debinding are deduced and discussed in terms of the decomposition of the binder components in the MIM feedstock.

Abstract: This study has examined the effects of using TPNR backbone polymer on the morphology and mechanical properties of the metal injection moulding feedstock 316L stainless steel with paraffin wax (PW) and palm stearin (PS) respectively as the main binder and stearic acid as a lubricant during mixing and injection moulding process. Tensile behaviour indicates that the green sample of feedstock PW/TPNR/SA system gives higher value compared to PS/TPNR/SA system. Morphology studies showed that green samples of PS/TPNR/SA exhibited brittleness fracture compared to PW/TPNR/SA system.

Abstract: Metal injection moulding (MIM) feedstock is a mixture of metal powder and binder. The function of the binder system is to provide flow ability of the metal particles and shape retention of the moulded parts. The behaviour of the feedstock depends greatly on the binder formulations and its composition. In these studies, the possibility of using thermoplastic natural rubber (TPNR) as a binder system has been preliminarily investigated. The TPNR binder containing of natural rubber (NR) and polyethylene (PE) were studied at variable compositions. The characterization includes of mixing parameter, mixing torque and SEM micrograph of TPNR. Results show that the optimum composition of NR is about 40% in volume fraction of TPNR binder. The rheological results of the feedstock are considered to be used in MIM process as bio-composite binder.