Fabrication of the Primary Coat of Ceramic Shell Mold for Investment Casting by Using Electrophoretic Deposition with Cylindrical Electrode

摘要

The surface roughness of casting is dependent on the primary coat of ceramic shell mold in the precision metal casting process. And the electrophoretic deposition (EPD) process has the following advantages, such as: simple facility, low cost, high deposition rate and high surface finish, therefore, this process has been widely applied to the fabrication of ceramic film. In this study, the EPD process was prepared to deposit the Al_2O_3 primary coat on the surface of the solid conductive plastics substrate. Then, the conventional dipping, stuccoing and drying operation of lost wax process were practiced repeatedly to build a certain thickness of ceramic shell mold. The effects of applied voltage, deposition time on the deposition behavior were also studied. The effect of thickness on permeability of ceramic shell mold was also studied. After the ceramic shell mold was prepared, the metal casting practice was operated. The surface roughness tester, modulus of rupture (MOR) measurement apparatus and high temperature permeability measurement apparatus were applied to measure the surface roughness, rupture strengths (high temperature strength and fired strength) and high temperature permeability of the ceramic shell mold; then, the surface roughness of the casting was also measured, too. The results showed: The permeability of ceramic shell mold was increased with the increase of the deposition thickness. With the same grain size of refractory, the surface of the ceramic shell mold fabricated by EPD process showed better surface roughness than that of the conventional shell building operation. As to the MOR, there was no significant difference between these two processes. The surface of the casting prepared by the EPD process had the superior surface roughness.