Abstract
The continuous improvements in micro-forging technologies generally involve process, material, and tool design. The field assisted sintering technique (FAST) is a process that makes possible the manufacture of near-net-shape components in a closed-die setup. However, the final part quality is affected by the influence of friction during the ejection phase, caused by radial expansion of the compacted and sintered powder. This paper presents the development of a pre-stressed tool system for the manufacture of micro gears made of aluminum. By using the hot isostatic pressing (HIP) sintering process and different combinations of process parameters, the designed tool system was compared to a similar tool system designed without a pre-stressing strategy. The comparison between the two tool systems was based on the ejection force and part fidelity. The ejection force was measured during the tests, while the part fidelity was documented using an optical microscope and computed tomography in order to obtain a multi-scale characterization. The results showed that the use of pre-stress reduced the porosity in the gear by 40% and improved the dimensional fidelity by more than 75% compared to gears produced without pre-stress.
Highlights
Micro-sintering enables the manufacture of micro-scale components with a complex shape and geometry
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This paper has presented the development of a pre-stressed tool system for the manufacture of micro gears made of aluminum [32]
Summary
Micro-sintering enables the manufacture of micro-scale components with a complex shape and geometry. The use of the pre-stress for a sintering tool was justified by the possibility of reducing the internal diameter of the die during the process. The designed tool system was tested under different sets of process parameters such as punch pressure (four levels: 75 MPa, 100 MPa, 125 MPa, and 150 MPa), sintering temperature (four levels: 450 ◦C, 500 ◦C, 550 ◦C, and 600 ◦C), and holding time (four levels: 10 min, 15 min, 20 min, and 25 min). A similar percentage force reduction was observed by varying either the punch pressure or theTsaibnlteer2i.nAgvtermagpeereajetuctrieo.n force reduction during the ejection as a function of the process parameters
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