Using Fused Silica as the Primary Coat of Ceramic Shell Mold for Investment Casting by Electrophoretic Deposition

• Main Authors: Chai-Chou Tsai, 蔡佳洲
• Other Authors: Koho Yang
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/13536812729372305763

碩士 === 國立高雄應用科技大學 === 模具工程系 === 100 === Fused silica has been used as the primary coat for investment casting by electrophoretic deposition (EPD). With the application of EPD, the arrangement of powder particles was improved to acquire a better surface roughness. The EPD process has the following advantages, such as: simple facility, low cost, high deposition rate, high surface finish and a variety of complex surface shape of conductive substances can be coated. In this study, EPD process was used to fabricate a fused silica primary coat on the conductive plastic, and was set for drying. Then, the conventional shell building process, i.e., dipping, stuccoing and drying were practiced and repeated for several times to obtain a certain thickness as the backup layers for the ceramic shell mold. The effects of applied voltage, current, time, pH, powder concentration and additives on deposition weight and thickness were studied, and the effects of add dispersant in suspension. Owing to the low physical bond strength of the powder, the EPD layer is easily to peel off; therefore, to increase the adhesion force of the layer by chemical bond, the polymer material has been added. The surface roughness, modulus of rupture (MOR, high temperature strength and fired strength) and high temperature permeability of the ceramic shell mold were examined, the effects of applied drying time on different processes, then observed and analysis wetting of ceramic shell mold and metal. Finally casting of aluminum alloy. The experimental results：Deposition weight of Fused silica was increased with the increase voltage, and deposition rate of Fused silica was reduce with the increase deposition time. It had to stable the suspension and increase the adhesion force of the layer that adding anionic type stearic acid and binder PVB. Comparison of the ceramic shell mold fabricated by EPD process with the conventional shell building by lost wax process, it were shorten the drying time and Improve the surface roughness to get batter surface roughness of casting by EPD, but high temperature permeability and MOR of the ceramic shell mold were somewhat less.