Study of phase transformations in CMSX-6 and CMSX-8 superalloys

Nickel-based superalloys are extensively used mainly in the aircraft and aeronautic industry, particularly in the hottest parts of engines or turbo-reactors. The phase reactions occurring in these heat-resistant materials play a crucial role in many aspects of the processing and service of the highly alloyed materials. Cast Ni-based superalloys are obtained in a complex way and their structure is complicated. Differential scanning calorimetry (DSC) technique was applied for determination of temperature ranges of the phase transformations occurring in the CMSX-6 and CMSX-8 superalloys during heating/cooling processes. Thermophysical properties, including temperatures of the phase transformation, are the critical input parameters in mathematical models of solidification and casting of metallic materials. The literature data concerning phase transformations and performance of the heat treatment for CMSX-6 and CMSX-8 are incomplete and ambiguous. DSC results accompanied by scanning electron microscopy characterization of microstructure of CMSX-6 and CMSX-8 superalloy was applied. The present study will improve the understanding of the fundamental mechanisms of phase transformations of single-crystal nickel-based superalloys.