No description available.

Published Article / Titanium has fired the imagination of engineers and designers for decades by its 'ideal' combination of high strength, low density and good corrosion resistance. However, its application has unfortunately been limited to those niche markets where performance is more important than cost, such as in the aerospace, military, medical and off-shore oil drilling fields. Extensive efforts have been and still are being expended on ways to make this metal cheaper. There are promising new processes but these have yet to be demonstrated commercially. Nevertheless, there has been a global surge in interest in titanium over the past decade, and in South Africa the government has recently made this a particular focus for research and development funding. With the increased availability of higher quality titanium powder, metal injection moulding offers an attractive method for producing small, intricate components at a reasonable cost. This paper will present an overview of the metal injection moulding process and discuss the particular challenges related to the use of titanium and titanium alloy powders. The state of the global and local industry and markets will also be reviewed.

No description available.

Published Article / Metal injection moulding (MIM) offers advantages for mass production of components over conventional production methods for parts with complex shapes and large production runs. The MIM process includes mixing a fine metallic powder with a polymeric binder to produce a homogeneous feedstock. This enables the production of metallic components in a similar manner to plastic injection moulding. After undergoing a process of binder removal the components undergo a conventional sintering cycle. As significant shrinkage occurs (as much as 30%) this must be considered when designing the die cavity. This paper describes the design and manufacture of a die to produce tensile specimens. Extensive injection moulding trials to produce acceptable tensile components were undertaken. The complexities and possible implications of the design of a mould on the process are discussed. The outcomes of this research will be used by the CSIR for further development and application of the MIM technology for manufacture of high value components, such as dental implants.

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. / The works done during this PhD focuses on the study of the thermo-physical behavior of bio sourced polymer blends loaded with Inconel 718 powder (feedstock) to be shaped by the Metal Injection Molding process (MIM). First, a review of the researches related to the MIM process was conducted to identify innovative materials and processes that can improve the MIM process. Thus, the use of polyethylene glycol (PEG), selected for its properties of solubility in water, and bio sourced polymers, in order to reduce the environmental impact, were selected. The bio sourced polymers have been selected in accordance with the conditions of the injection molding process, and the choice was made to use polylactic acid (PLA) and polyhydroalkanoates (PHA and PHBV). Similarly, the supercritical CO2 as solvent was chosen to reduce the time of binder removal as well as increasing the quality of components produced. Thermo-physical, mechanical and rheological characterizations were made to determine the behavior of the different feedstock formulations. The results showed a degradation of the PEG and of the stearic acid under the conditions of use of the biopolymers, during the mixing and the injection stages. The use of feedstock made of bio sourced polymers have improved the homogeneity of the injected components, but they have generated defects during the debinding step. These defects have been eliminated by the use of CO2 in the supercritical state as solvent of the PEG. This method has significantly decrease the time of binder removal and improved the quality of the final components. Finally, densified components have the mechanical properties corresponding to Inconel 718.