The Effect of Fused Silica Crystallization on Flexural Strength and Shrinkage of Ceramic Cores for Investment Casting

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 degrees C to 1400 degrees C for various dwelling times (6 h to 48 h). Sintering above 1300 degrees C for 12 h and dwelling time over 24 h at 1200 degrees 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 degrees C for 12 h endured wax patterning and shell molding, and was manufactured successfully.