Calculation of Thermophysical Properties of Ni-based Superalloys

Abstract

Reliable thermophysical data of Ni-based superalloys are needed for the mathematical modelling of solidification in casting applications. This paper derives equations and procedures to calculate the following properties of these alloys from chemical composition of the alloy: the gЈ phase content, liquidus and solidus temperatures, density and thermal expansion coefficient, heat capacity and enthalpy, electrical resistivity, thermal diffusivity and conductivity, viscosity, surface tension and contact angle. Estimates are also for the diffusion coefficient and emissivity. This work has revealed an urgent need for reliable property measurements on liquid Ni-based alloys for the following: heat capacity, electrical resistivity, thermal diffusivity and conductivity, emissivity and diffusion coefficients.

Thermophysical properties of some Ni-based superalloys in the liquid state relevant for solidification processing

“…The surface tension values of both ternary alloy systems calculated by the Toop model differ up 4.2 % from the new experimental values and all ternary values are slightly lower with respect to the Al-Ni values predicted by the CFM(Table 4). A comparison of measured and calculated values for the Ni-based superalloys analyzed is listed inTable 4, indicating that both model-based predictions substantiate fairly well the new surface tension experimental data and can be interpreted as a lower bound for the measured values in agreement with the findings reported by Mills et al[21] related to uncertainty in the model-based predictions for different thermophysical properties of Ni-based superalloys. Indeed, in the case of surface tension, an uncertainty of about ±5 % was found.…”

“…It is worth to be noted that the differences between the present experimental data and those predicted become larger from the alloy melting point to the end of the temperature interval of measurements due to different density temperature coefficients with respect to the calculated curves [15,21].…”

“…8, the surface tension data of CMSX-4 [22] result lower than expected with respect to the Al content in the entire temperature range of measure. However, the surface tension of CMSX-4 as a function of temperature has been widely discussed in the literature [16,21,23,24], showing that its surface tension values exhibit a large scatter. That reveals the difficulty of obtaining reproducible results which seems to be particularly influenced by the combined effects of highly reactive elements, such as Ti and Re [12,16] and gaseous surfactants [9].…”

Density, Surface Tension, and Viscosity of CMSX-4® Superalloy

“…Another model was suggested by Mills [29] giving the theoretical relationship between density and temperature, as follows: (8) In this case, the deviation between the measured data and the calculated values was less than 1.5%.…”

Corrections for Thermal Expansion in Thermal Conductivity Measurement of Insulations Using the High-Temperature Guarded Hot-Plate Method

“…Since the thermal expansion of any coatings applied to a heater plate would need to be well matched, these data for nickel 201 can be used when selecting high-temperature, high-emissivity coatings. These data could also be used for verifying the models that calculate the thermophysical properties of nickel-based alloys [10].…”