Resumen de Physical simulation of investment casting of Mar-M247 Ni-based superalloy
Mehdi Rahimian
Mar-M247 is a Ni-based superalloy developed for high temperatures applications, such as advanced jet engines, where high strength and excellent creep resistance are required. Investment casting process has been widely used for fabrication of complex shape parts and is only commercially technique for fabrication of nozzle guide vanes (NGVs) known as a one of the most important structural parts of engines and gas turbines. Nevertheless, the development of NGVs is hindered by the complexity of investment casting process of complex shape parts. Therefore, there is high demand to find and apply a method to overcome those drawbacks. Physical simulation of investment can be a method to tackle these shortcomings. Physical simulation of investment casting was developed to mimic solidification of alloy during investment casting of new generation NGVs from Mar-M247 by high capability physical simulator machines. This tool, consisting of thermal model and melting/solidification experiments, is the exact reproduction of the thermal and mechanical history of full scale investment casting process in the laboratory scale. Initially, the Pro-Cast based thermal model was developed, validated and applied to predict local cooling rates at defined points of NGVs. Then, the outcomes of the modeling were used as input parameters for the melting/solidification experiments in the thermo-mechanical simulator Gleeble 3800. Finally, the validation of physical simulation was carried out by comparison of microstructural and hardness properties of Gleeble specimens and as-cast NGV. In addition, in order to get a deeper insight into the correlation between Mar-M247 characteristics with casting/solidification conditions. Complementary study on SDAS showed that temperature gradient should be taken into account as an effective factor influencing the SDAS. Furthermore, the skin formation and its grain texture were studied by utilizing the combination of electron back skater diffraction (EBSD) and nanoindentation method.
