Properties of fiber reinforced plaster molds for investment casting
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https://doi.org/10.1007/s41230-020-0056-9
Properties of fiber reinforced plaster molds for investment casting Jie Ren1, *Xiang Chen1, 2, Yan-xiang Li1, 2, Yuan Liu1, 2, Hua-wei Zhang1, 2 1. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China 2. Key Laboratory for Advanced Materials Processing Technology, Tsinghua University, Beijing 100084, China
Abstract: In order to improve the performance of plaster molds for investment casting, a diverse content of glass fiber and polypropylene (PP) fiber was incorporated into the slurry for the preparation of a fiber-reinforced mold. The green and fired bending strengths, thermal expansion properties, permeability, and thermal shock resistance of the mold were examined, and the scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) was applied for the observation of fracture morphology. With appropriate content, the introduction of glass fiber was proved to increase the green bending strength and fired bending strength, restrain the thermal expansion and improve the thermal shock resistance of the mold, while the polypropylene fiber added was able to raise the green bending strength and the permeability, reduce the thermal expansion and heighten the thermal shock resistance as well, though the fired bending strength would be weakened slightly. Evenly distributed fibers were capable of enhancing the mechanical properties of the matrix, but agglomerations and bundles of fibers resulting from excessive addition had a negative impact. Meanwhile, it was also manifested that micropores left by ablative polypropylene fibers could improve the permeability and reduce the thermal expansion of the mold, and the fired bending strength would be decreased slightly by the deterioration of continuous structure. Three different ratios of hybrid fiber were employed in plaster molds, which can meet altered requirement of castings. The samples modified with hybrid fiber possessed lower thermal deformation, higher air permeability, and better resistance of thermal shock, while the mechanical strength was equal to the fiber free sample or slightly increased. Key words: plaster mold investment casting; fiber-reinforced; bending strength; thermal expansion; permeability; thermal shock resistance
CLC numbers: TG221+1
Document code: A
P
laster mold investment casting, as an advanced casting technology, has been widely applied in aviation, electronics, etc. Due to its simple preparation, effortless demolding, and promising replication of investment casting molds, plaster molds are commonly employed in the manufacture of thin-walled complex castings with high precision demand [1-3]. According to the requirements of molds suggested by Jones and Yuan [4], a qualified mold is supposed to have sufficient strength and thermal shock resistance to withstand the impact of external forces during various processes in casting, while high dimensional stability
*Xiang Chen Male, born in 1970, Ph.D., Professor. His research interests mainly focus on cast
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