Bending strength and fracture surface topography of natural fiber-reinforced shell for investment casting process

Abstract

I nvestment casting has been widely used to manufacture castings for centuries, due to its advantages of producing high quality castings with excellent surface finish, dimensional accuracy, and near-net shape. Especially, it is useful for castings with complex cavities in its body, which could not be fabricated by forging or machining, or where machining would be too wasteful of materials. Its applications include art castings, turbine blades and many more industrial components [1] . Jones and Yuan [2] pointed out that, in order to achieve a higher ability to resist cracking during dewaxing and casting, an investment casting mould must have sufficient green strength to withstand wax removal without failure as well as high thermal shock resistance to prevent cracking during metal pouring. Heat permeability is required to promptly evacuate air and other entrapped gases during metal filling. At the same time, it is possible to break shells quite easily without causing any damage to castings when the molten metal in the shell has solidified Abstract: In order to improve the properties of silica sol shell for investment casting process, various contents of cattail fibers were added into the slurry to prepare a fiber-reinforced shell in the present study. The bending strength of fiber-reinforced shell was investigated and the fracture surfaces of shell specimens were observed using SEM. It is found that the bending strength increases with the increase of fiber content, and the bending strength of a green shell with 1.0 wt.% fiber addition increases by 44% compared to the fiber-free shell. The failure of specimens of the fiber-reinforced green shell results from fiber rupture and debonding between the interface of fibers and adhesive under the bending load. The micro-crack propagation in the matrix is inhibited by the micro-holes for ablation of fibers in specimens of the fiber-reinforced shell during the stage of being fired. As a result, the bending strength of specimens of the fired shell had no significant drop. Particularly, the bending strength of specimens of the fired shell reinforced with 0.6wt.% fiber reached the maximum value of 4.6 MPa.

The Influence of Shell Mold Composition on the As-cast Macro- and Micro-structure of Thin-Walled IN713C Superalloy Castings

“…Molds should be adequately porous and gas permeable, required to evacuate air and other entrapped gases promptly during melt pouring. For these reasons, some research has been undertaken to develop a fabrication method for reinforcing thin molds (Ref [13][14][15]. One trend in the development of binders in investment casting is the introduction of ceramic or polymer fibers in the slurry for increasing mold strength ( Ref 13).…”

Analysis of the slurry and ceramic properties for investment casting obtained with domestic colloidal silica binders

“…Для определения механических свойств изготавливали керамические образцы в виде параллелепипедов для испытаний на изгиб [24].…”

“…Обычно «сырая» прочность керамики примерно в 2 раза меньше, чем в прокаленном состоянии [17,18,25]. Полученные значения очень близки к результатам других работ [10,17,24].…”

“…6. Соотношение между значениями вязкости суспензии, определенными с помощью вискозиметра ВЗ-4 (X ) и ротационного вискозиметра (Y ) Наиболее часто применяют керамические формы с прочностью на изгиб от 3-10 МПа [10,17,24,31]. Использование исследуемых связующих материалов позволит обеспечить указанные значения даже в неспеченном состоянии, за исключением вариантов, где суспензия обладает низкой условной вязкостью (~20 с) и ис-пользуется крупная фракция плавленого кварца (ПК 0,5-1,0 мм).…”

“…Цветная металлургия • 2023 • Т. 29 • № 2 • С [15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”