Microstructural characteristics and thermophysical properties of spark plasma sintered Inconel 738LC

Nickel-based superalloys are used for turbine component parts in the power industry, aircraft engines, and in the marine sector. One such alloy that is available for these purposes is Inconel 738LC (IN738LC) nickel-based superalloy. Therefore, it is pertinent to have good structural and thermal stabilities for high-temperature applications, since these characteristics are important for its performance. In this study, spark plasma sintering technology was used to fabricate IN738LC nickel-based superalloy by using sintering temperature in the range of between 900 and 1200 °C. The fabricated products were characterized by using the scanning electron microscope and X-ray diffraction. There was the formation of the γ′(Ni₃(Ti, Aℓ)) intermetallic phase in the microstructure, which contributed to the material (Inconel 738LC) property. The solid solution elements present are chromium, cobalt, tungsten, and tantalum; these equally contribute to the structural stability of IN738LC. The density, hardness, and the predicted yield strength increased with increasing sintering temperature, while the porosity decreased with increasing sintering temperature. The thermal conductivity, which is an important thermophysical property of IN738LC, enables the evaluation of the usefulness and service life of IN738LC superalloy at high-temperature applications, was also examined. The thermal conductivity was measured by using a laser flash method in the temperature range of 100–600 °C. For the sintered alloy, the thermal conductivity was determined as a function of the thermal diffusivity, specific heat capacity, and density. Analysis showed inflection pattern with increase in temperature on the sample fabricated at 900, 1000, and 1100 °C, ; a monotonic increase with increase in temperature was observed on the sample fabricated at 1200°C, ; the inflections are associated with the γ′ precipitates dissolution and redistribution.