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The diffusion of Os in Ni is characterised by measuring interdiffusion coefficients in the binary Ni-Os system, in the temperature range 1200-1350°C. The results are compared with data for Ni-Re. Theoretical calculations indicate that Os should display a diffusion coefficient comparable with Re, among the lowest displayed by elements from the d-block transition elements. The authors' experimental findings confirm these predictions, and suggest that alloying with Os is likely to improve the high temperature properties of the nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Thermophysical properties for the solid and liquid phases of several Ni based superalloys (CMSX-4, CMSX-10, CM186LC, IN 738 and Rene 80) have been measured. The following properties were measured: heat capacity and enthalpy, thermal expansion coefficient and density, thermal diffusivity, viscosity and surface tension. Analysis of these measurements showed that that γ' phase (Ni3Al) affected the values for the following properties; Cp, enthalpy, electrical resistivity, thermal diffusivity and conductivity. Relationships have been identified between properties and the γ' phase content (which can be represented by mass% Al in the alloy). These relations were then used to calculate property values of the alloys from chemical composition. Other relations were developed to estimate the viscosities and surface tensions of Ni based superalloys. The predicted property values were found to be in good agreement with the measured values. [ABSTRACT FROM AUTHOR]