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Second and third generation single crystal (SX) Ni-based superalloys are considered to be sensitive to microsegregation, 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.

A third-generation single-crystal (SX) superalloy was heat treated at 1350 °C for 24 hours while being exposed to nickel vapor. It is observed that a layer of 60-µm thickness deposited onto the alloy. This prevented the formation of TCP phases and the occurrence of melting, which were reported in previous studies. The interdiffusion between the alloy and deposited layer shows strong indications of cross-diffusion effects, as shown from the composition profile measurements and simulations.