Impact of holding time and heating rate on the creep behavior of silicon-based ceramic cores during preheating

High-performance aerospace engines require extremely precise turbine blades, making it essential to understand the factors and mechanisms that influence the creep deformation of ceramic cores. In this study, silicon-based ceramic cores were preheated and insulated in a muffle furnace. By combining simulations and experiments, we found that both extending the holding time and increasing the heating rate resulted in greater creep deformation of the ceramic cores. Analysis of the heating microstructure and phase transformation revealed that a longer holding time reduced the volume of cristobalite, decreased the viscosity of the liquid phase, facilitated the reaction between corundum and molten quartz, and enhanced the relative sliding between phases. Conversely, a higher heating rate led to a reduced content of corundum, which in turn decreased the liquid phase viscosity and weakened the Zener pinning effect of mullite, thus impairing its ability to hinder viscous flow. As a result, the primary mechanism for the increase in creep deformation during preheating of silicon-based cores is the reduction in liquid phase viscosity. Based on these findings, we propose a “stepped” heating method that reduces the heating rate while maintaining constant heating time. This approach achieves a more uniform heating rate and effectively reduces the amount of creep deformation.