Thermophysical properties of Ni based super alloy 617

- In this study, various thermophysical properties of alloy 617 have been reported.
- Experimental and theoretical approaches are used to estimate these properties.
- Variation of these properties are correlated with microstructure of alloy 617.
- Alloying addition and various precipitates play significant role on these data.
- Alloying addition and magnetic ordering significantly govern thermal conductivity.

In this study thermophysical properties of alloy 617 have been measured as a function of temperature using various thermal analysis techniques and complemented by structural and microstructural characterization. The enthalpy increment (HT−H298) has been measured using static calorimetry in the temperature range of 300-1523 K. It is found that (HT−H298) increases monotonically with temperature up to about 1000 K. However, above this temperature two distinct inflections are detected at about 1030 K and 1205 K respectively. A critical comparison of these inflections with Thermo-Calc simulations and dynamic calorimetry measurements indicates that they are associated with dissolution of M23C6, and γ′-Ni3Al phases respectively. The enthalpy data has been numerically fitted using non-linear regression analysis to obtain the temperature dependence of heat capacity. Further, the thermal diffusivity and thermal expansivity of alloy 617 have been measured using the laser flash method and thermo-mechanical analyzer in the temperature range of 300-1523 K. Finally, with the knowledge of heat capacity, density and thermal diffusivity data, thermal conductivity has also been estimated in the temperature range of 300-1523 K. The measured properties for alloy 617 have been compared with Thermo-Calc, JMatPro simulation and other literature data, which clearly establishes the role of precipitates dissolution. The various properties measured in the present study are original and new addition to the database for alloy 617, which can serve as new input for Thermo-calc based optimization. This paper also provides the insight into the temperature and composition dependence of thermal conductivity of alloy 617.