Papers by Keyword: Binder System

Abstract: The demand for components manufactured by Metal Injection Molding (MIM) has been increased due to a diverse range of applications on the high temperature mechanical properties and corrosion/oxidation resistance. Super alloy utilize the inherent physical properties of heat-resisting alloy based on iron-nickel, or cobalt specifically high purity and fine particle size distributions, which can enhance sintering and maximize the density of the final component. The development of super alloy Inconel 718 (IN718) using MIM is discussed. IN718 powder with binder formulation consists of polyethylene (PE) / palm stearin (PS) were mixed homogeneously and injected to produce green compacts. The binders then were removed through solvent extraction process from various heating temperature and duration of time. The binder removal was quantified by weight loss measurements and the evolution of pore structure for the debound specimens was observed using scanning electron microscope (SEM). Result shows that complete extraction of PS from the green parts can be concluded during 60 °C of heating and 6 hours of immersion in heptane.

Abstract: MIM technique is described in which allows for the production of highly porous metallic foams with porosity levels up to 90%. It makes use of the pressure built up by the decomposition of a foaming agent which is incorporated in a foamable precursor copper material obtained by powder compaction. A suitable behaviors feedstock that refers to its rheological is one of the key factors to ensure the successful of MIM technique and to predict failure, whether due to the binder component and compositions, powder loading or unsuitable process parameters. Potassium carbonate and polyethylene is added and were mixed homogeneously to form a copper feedstock. The rheological results in term of shear rate, shear stress, viscosity, melting rate and softening temperature which related to pseduoplastic behaviors have been conducted using a capillary rheometer (CFT-500D, Shimadzu) at various temperature and loads. The result has indicated that the viscosity of the feedstock is decreased with increasing shear rate thus proved the feedstock to be pseudoplastic.

Abstract: Inconel 718 has been widely used as a super alloy in aerospace application due to the high strength at elevated temperatures, satisfactory oxidation resistance and heat corrosion resistance. In this study, the Inconel 718 with different solid loading (System A - 50/50 vol.% and System B - 60/40 vol.%) has been fabricated using high technology of Metal Injection Moulding (MIM) process due to the cost effective technique for producing small, complex and precision parts in high volume compared with conventional method through machining. Through MIM, the binder system is one of the most important criteria in order to successfully fabricate the Inconel 718. Even though, the binder system is a temporary, but failure in the selection and removal of the binder system will affect on the final properties of the sintered parts. Therefore, the binder system based on palm oil derivative which is palm stearin has been formulated and developed. The rheological studies of the mixture between the powder and binders system have been determined properly in order to be successful during injection into injection moulding machine. After moulding, the binder holds the particles in place. The binder system has to be removed completely through debinding step. During debinding step, solvent debinding and thermal pyrolysis has been used to remove completely of the binder system. The debound part is then sintered to give the required physical properties.

Abstract: Micro powder injection molding has been accepted as a potential forming technology for large-scale production of miniature components in industries. However, mold filling capability is often poor due to the blind hole structure of the die cavity, which restricts the widespread application of this technique. In this paper, ZrO₂ micro gears with addendum circle ranging from 900μm to 200μm were studied. Instead of using traditional PW-HDPE-SA binder as in powder injection molding, thermoplastic binder system is optimized here for better replication of micro gear. It is found that the dimensional accuracy and demold after injection molding can be improved by utilizing proper binder system. ZrO₂ feedstock with a powder loading of 46vol.% and the binder system consisting of BW, HDPE and SA was successfully injection molded and demolded, which indicates good mold filling capability and sufficient demolding strength. The binder system was successfully removed by debinding process in two steps, solvent debinding followed by thermal debinding. Debound components free of defects were obtained. Keywords: Micro powder injection molding, ZrO₂ feedstock, Binder system, Molding filling capability, Demolding strength

Abstract: The influence of a binder system to the rheological behavior of a Metal Injection Molding (MIM) feedstock is presented in the paper. The binder systems used are: a) PEG & PMMA b) Palm stearin & LLDPE and, c) Tapioca starch & LLDPE. The viscosity and shear rate of the feedstocks were measured at various range of temperature and shear rate across the L/D = 10 capillary rheometer. The flow behavior index, n and activation energy, E of each feedstock were measured to show its significance as MIM feedstock. Generally, the result indicates all feedstock exhibits a shear thinning behavior and the binders are suitable as MIM binder. Additionally, the present paper has discovered that the binder system does not have much influence to the activation energy. In order to show the relevance of the rheological behavior to the actual injection molding performance, green parts has been injection molded and the result shows an agreement with the rheological behavior result.

Abstract: Metal Injection Molding (MIM) is a cost-effective technique for producing small, complex, precision parts in high volumes. MIM consists of four main processing steps: mixing, injection molding, debinding and sintering. In the mixing step, the powder titanium alloy (Ti6Al4V) medical grade is mixed with a binder system based on palm stearin to form a homogeneous feedstock. The rheological studies of the feedstock have been determined properly in order to success during injection into injection molding machine. After molding, the binder holds the particles in place. The binder systems then have to be removed completely through debinding step. Any contamination of the binder systems will affect the final properties of the parts. During debinding step, solvent extraction debinding has been used to remove partly of the binder systems. The debound part is then sintered at high temperature under control atmosphere furnace. The properties of the sintered craniofacial implants then was measured and compared. The sintered craniofacial implants also then were determined in term of in-vitro cytotoxicity study using mouse fibroblast lines L-929. The results show that the sintered craniofacial implants of titanium alloy produced by MIM fullfill the in-vitro cytotoxicity test.