Investigation of casting–ceramic shell mold interface thermal resistance during solidification process of nickel based superalloy

Abstract

The study of thermal resistance (TR) at the casting-mold interface has been performed to describe the solidification process aimed at the improvement of technology and the reduction of defect quantity of investment castings. The analysis of thermal resistance at casting–mold interface between the solidifying IN 713C nickel superalloy plate casting and ceramic shell mold has been presented. The temperature measurements in the plate casting of IN 713C nickel superalloy and the ceramic shell mold were carried out to determine the casting–mold interface heat transfer coefficient (IHTC) with the use of inverse heat conduction method. The calculations were performed using a ProCAST software. It was found that the casting–mold IHTC (7962Wm−2K−1) was the highest for the alloy in the liquid state and then it intensively decreased during solidification and cooling followed by its increase close to the end of the solidification process forming another peak on the obtained curve. The formation mechanism of gap between the ceramic mold and Ni based superalloy casting as well as another peak were proposed taking into account the occurrence of mixed oxide scale at the interface. On the basis of numerical simulation, it was found that the IHTC had less influence on cooling rate of casting than the thickness, thermal conductivity and emissivity of the mold for the applied technological parameters of the process.