Thermodynamic Study of Single Crystal, Ni-based Superalloys at the γ+γ’ Two-phase Region Using Knudsen Effusion Mass Spectrometry, DSC and SEM.

Abstract Second and third generation single crystal (SX) Ni-based superalloys are considered to be sensitive to microsegragation, incipient melting and microstructural instability. Thus, their thermodynamic properties and stability at high temperatures are of key importance. Vapour composition consisting of four species has been detected in the temperature range 1453-1573 K. This was found after studies of three single crystal Ni-based superalloys CMSX-4, CMSX-10K and CMSX-10N using the method of Knudsen Effusion Mass Spectrometry (KEMS). The activities of Ni, Co, Cr, and Al have been determined in the γ+γ', two-phase region. A series of Differential Scanning Calorimetry (DSC) measurements were carried out at various ramping up rates to determine phase transition temperatures; the γ' solvus, the solidus and the liquidus temperature were obtained. Back-scattered Electron Imaging (BEI) and Energy Dispersive Spectroscopy (EDS) measurements were performed and depicted the effect post KEMS for such complex multicomponent systems.