Single crystal investment casting technologies have been utilized for aircraft gas turbine blades where high yields are commonly achieved. These yields are the result of 30 years efforts in understanding the relationship between alloy, geometry and process conditions. The goal of this program was to develop and improve technologies for single crystal and directionally solidified castings to benefit large industrial and utility gas turbine engines. One focus was on defining and implementing advanced vacuum induction melting (VIM) furnace enhancements that provide improved control of temperatures during solidification. The emphasis was on improving the thermal gradients during the solidification phase. Casting efforts have demonstrated an increase in the maximum thermal gradient of 20 to 30%, and approximately 100% increase in the minimum thermal gradient. The second focus was investigation of the resistances to improving thermal gradients and solidification rates during the investment casting process. Addressing these resistances to heat transfer in a casting process provide guidance on where improvements can be made. A sensitivity evaluation using finite-element-modeling has shown the relative levels of the significant factors.
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