Simulation of the temperature distribution on the mold surface and inside casting during high-gradient directional solidification

Abstract

In order to determine the temperature gradients in ingots fabricated by the directional solidification (DS) using an UVNS-6 installation produced by VIAM (Moscow), single-crystalline ingots made of VZhM3 nickel superalloy have been prepared. Herewith, DS technologies with liquid-metal cooling (LMC) and without it are used (the Bridgman–Stockbarger method). A tin melt is used as the LMC. Readings of thermocouples installed on the surface of a ceramic mold are recorded during ingot DS. The DS of ingots made of VZhM3 nickel superalloy using the UVNS-6 installation is simulated in the ProCast program using thermal properties of the alloy, ceramic mold, and parts of the DS installation found in articles, as well as boundary conditions between them (interface heat-transfer coefficients). The good coincidence of the calculated and experimental temperature distributions in the mold during solidification using the Bridgman–Stockbarger and the LMC technique is shown, which makes it possible to use simulation of the ingot fabrication in the ProCast program to predict the temperature gradient at the solidification front, the solidification front profile, and the size of the mushy zone (where the dendritic alloy structure is formed). The temperature gradient attained in the ingot in the case of using the Bridgman–Stockbarger method by the results of simulation was 36°C/cm. The temperature gradient in the case of applying the LMC technique is 204°C/cm; i.e., it turned out sixfold higher than that attained when using the Bridgman–Stockbarger technique. Thermal properties and boundary conditions can be demanded when performing computer simulating of nickel superalloys blade casting process.