The binder plays the most important role in the metal injection molding (MIM) process. It provides fluidity of the feedstock mixture and adhesion of the powder to keep the molded shape during injection molding. The binder must provide strength and cohesion for the molded part and must be easy to remove from the molded part. Moreover, it must be recyclable, environmentally friendly and economical. Also, the miscibility between polymers affects the homogeneity of the injected parts. The goal of this study is to develop a feedstock of superalloy Inconel 718 that is environmentally friendly. For these different binders, formulations based on polyethylene glycol (PEG), because of his water solubility property, and bio sourced polymers were studied. Polyhydroxyalkanoates (PHA) were investigated as a bio sourced polymer due to its miscibility with the PEG. The result is compared to a standard formulation using polypropylene (PP). The chemical and rheological behavior of the binder formulation during mixing, injection and debinding process were investigated. The feedstock was characterized in the same way as the binders and the interactions between the powder and the binders were also studied. The results show the well adapted formulation of polymer binder to produce a superalloy Inconel 718 feedstock.

In the MIM process the binder play the most important role. It provides fluidity of the feedstock mixture for injection molding and adhesion of the powder to keep the molded shape. The binder must provide strength and cohesion for the molded part, must be easy to be removed from the molded part, and must be the recyclable, environmentally friendly and economical ones. The goal of this study is to develop a binder environmentally friendly. For this, a study of formulation based on polyethylene glycol, because of is water debinding properties, was made. Polylactic acid and Polyhydroxyalkanoates were investigated as bio sourced polymers. The chemical, miscibility and rheological behavior of the binder formulation were investigated.

Produce in large quantities small precision components with complex shape which would be costly to produce by alternative methods. MIM is a process which combines the versatility of plastic injection moulding with the strength and integrity of machined, pressed or otherwise manufactured small, complex metal parts. MIM consists in shaping powder particles and sintering them. During the injection phase, segregation appears in the feedstock and defects will be appear in the component during the sintering. To limit this effect, during decades a vast variety of binder systems have been developed. Binder systems are formulated as a mixture of different organic or inorganic substances with several functions. Binder system has the main commitments of giving the necessary rheological behavior to the feedstocks for injection moulding to transport the powder particles into the mould cavity and the cohesion of the green part. In this paper a study of chemical interactions between polymers in binder and in Inconel feedstocks was investigated by Fourier Transform InfraRed spectroscopy (FTIR) and by differential scanning calorimetry (DSC). These methodologies were also investigated to study the thermal behavior of the binder at a temperature close to the temperature of injection. Analyzes shows relationship between chemical interactions and miscibility of polymer and different rheological and mechanical behavior. All methodologies revealed no interactions between the different component of the binder and the powder. This result shows the necessity to develop a better formulation of binder to improve the homogeneity of the feedstock and reduce the segregation during injection phase.

Ces travaux de thèse concernent l’étude du comportement thermo-physique de mélanges de polymères biosourcés chargés de poudre d’Inconel 718 mis en forme par Moulage par Injection de poudre Métallique. Des matériaux et procédés innovants pouvant permettre une amélioration du procédé ont été étudiés. L’utilisation de polyéthylène glycol (PEG), choisi pour ses propriétés de solubilité dans l’eau, et de polymères biosourcés, pour diminuer l’impact environnemental, ont été choisi. Les nuances de polymères biosourcés ont été choisies adaptées aux conditions du procédé de moulage par injection, il s’agit d’acide polylactique et de polyhydroalcanoates. De même, l’utilisation du CO2 à l’état supercritique comme solvant, a pour objectif de diminuer le temps de déliantage ainsi que d’augmenter la qualité des composants réalisés. Les résultats obtenus ont montré une dégradation du PEG et de l’acide stéarique lors des cycles de mélangeage de de moulage par injection dans les conditions d’utilisation des polymères biosourcés. L’utilisation des mélanges chargés composés de polymères biosourcés ont permis d’améliorer l’homogénéité des composants injectés, mais ont engendré des défauts lors de l’étape de déliantage. Ces défauts ont pu être éliminés par l’utilisation de CO2 à l’état supercritique comme solvant du PEG. Ce dernier procédé a permis une diminution importante du temps de déliantage ainsi qu’une amélioration de la qualité des composants finaux. Les composants densifiés possèdent les propriétés mécaniques correspondantes à l’Inconel 718.