Papers by Keyword: Coarse Powder

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Authors: A.P.G. Nogueira, Ricardo Machado, Paulo A.P. Wendhausen, Diego Fernando Portaluppi
Abstract: Research on determined alloys produced by metal injection molding has been done for cost reduction purposes through the use of powders with bigger particle size. However, regarding feedstock homogeneity, certain limitations are presented when coarse particles are used. For instance, homogeneity strongly influences rheological behavior of the feedstock and dimensional control of the sintered part. Therefore, the purpose of this work was to evaluate effectiveness of a modified binder system with the addition of a surfactant polymer which makes the feedstock more homogeneous. This study was carried out on a FeNiP alloy currently processed by MIM, where 50%wt of the iron powder was replaced with course powder having a particle size distribution of D90 less than 47 ,m. Effectiveness of binder systems using a Melt Flow Index (MFI) and the behavior of dimensional accuracy at sintered part were analyzed. Results showed more feedstock homogeneity and less dimensional deviation when a surfactant agent was used.
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Authors: José M. Contreras, Antonia Jiménez-Morales, José M. Torralba
Abstract: The MIM technology is an alternative process for fabricating near net shape components that usually uses gas atomised powders with small size (< 20 μm) and spherical shape. In this work, the possibility of changing partially or totally spherical powder by an irregular and/or coarse one that is cheaper than the former was investigated. Different bronze 90/10 components were fabricated by mixing three different types of powder: gas atomised spherical powder (usual MIM powder < 22 μm) and two water atomised irregular powders (size < 35 μm and < 140 μm). The blends were made by using only two types of powder in each mixture with the following volume proportions (100/0, 67/33, 33/67, 0/100). The influence of the particle size and shape on the powder packing density and sintering stage was analyzed through the apparent density of the powder blends, as well as, densification, hardness and porosity of the sintered parts. The addition of irregular and/or coarse powder was found to affect the moulding process, although good densifications and hardnesses were obtained in the sintering step. Therefore it could be a promising way to diminish production costs in this technology.
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