Investigation of Thin-Walled IN718 Castings by Counter-Gravity Investment Casting

Abstract

Adjusted pressure casting is one kind of counter-gravity precision forming method in which the filling processes are at low counter-pressure while the solidification process are at high pressure. It aims at increasing the filling capacity for complex thin-walled castings and also provides an opportunity of introducing automatic control into the process by changing the pressure under which the metal is forced into the mold cavity. The filling capacity and solidification microstructure of complex thin-walled IN718 castings has been studied by experimental and numerical simulation. The results show that the liquid metal can flow through the mold cavity easily by imposing very low pressure. The average grain size of the 200mm×200mm×1mm thin walled IN718 casting piece varies from about 500μm to 800μm under different crystallization pressures. The average grain sizes are much smaller than those in the gravity casting process. Therefore, adjusted pressure casting is the promising technology for producing the complex thin-walled superalloy castings.