The effect of fused silica crystallization on flexural strength and shrinkage of ceramic cores for investment casting

Abstract

Complex designed silica-based ceramic cores were fabricated by ceramic injection molding. Slow heating rate (0.2K/min) for debinding restrained bloating on the surface of ceramic cores. To investigate effect of sintering conditions on mechanical properties of ceramic cores, green bodies were sintered at temperatures in a range from 1150 °C to 1400°C for various dwelling times (6 h to 48 h). Sintering above 1300°C for 12 h and dwelling time over 24 h at 1200°C reduce the flexural strength and increase the linear shrinkage of ceramic cores. Cristobalite, formed by high sintering temperature or long dwelling time, induces reduction of mechanical properties due to its phase transformation, which is accompanied by volume contraction and microcracking. Ceramic core sintered at 1200°C for 12 h endured wax patterning and shell molding, and was manufactured successfully.This work was supported by the Power Generation and Electricity Delivery Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), which was granted financial resources from the Ministry of Trade, Industry and Energy, Republic of Korea (2014101010187B)