Inconel 718: An In-depth Analysis of Thermal Conductivity vs Temperature

Inconel 718, a nickel-chromium alloy that is precipitation-hardenable, showcases a unique blend of strength, corrosion resistance, and weldability. It’s widely employed in diverse sectors from aerospace to nuclear reactors. This article delves deep into the thermal conductivity of Inconel 718 against temperature, offering a comprehensive understanding of this material’s thermal behavior.

Introduction to Inconel 718

Inconel 718, a potent superalloy, is renowned for its exceptional mechanical properties, even at very high temperatures. Developed in the 1960s, this superalloy has become the material of choice for numerous applications, especially in the aerospace industry.

Chemical Composition of Inconel 718

Inconel 718’s excellent properties stem from its unique chemical composition. The primary constituents include nickel, chromium, iron, niobium, molybdenum, aluminum, and titanium. It also contains trace amounts of other elements like boron and copper.

ElementContent (%)
Nickel + Cobalt50 – 55
Chromium17 – 21
Molybdenum2.8 – 3.3
Niobium + Tantalum4.75 – 5.5
Titanium0.65 – 1.15
Aluminum0.2 -0.8
Carbon0.08 max
Manganese0.35 max
Silicon0.35 max
Copper0.30 max
Boron0.006 max

Physical Properties of Inconel 718

Inconel 718 showcases a range of physical characteristics that contribute to its wide-ranging applications. The alloy’s density is approximately 8.19 g/cm³, and it exhibits a melting range of 1260 – 1336 °C. Moreover, it possesses a specific heat capacity of 435 J/kg.K and a coefficient of thermal expansion of 13.0 µm/m.K.

Mechanical Properties

The mechanical properties of Inconel 718 are significantly enhanced through precipitation heat treatment. At room temperature, the alloy displays an ultimate tensile strength of 180 ksi, yield strength of 150 ksi, and 12% elongation.

Heat Treatment

Heat treatment plays a crucial role in optimizing the properties of Inconel 718. A commonly used heat treatment involves heating at 1750 – 1800°F followed by air cooling, then heating at 1325°F and cooling at 100°F/hr to 1150°F.

Thermal Conductivity of Inconel 718

Thermal conductivity is a measure of a material’s ability to conduct heat. For Inconel 718, the thermal conductivity is approximately 11.4 W/m.K, which contributes to its excellent performance in high-temperature applications.

Effects of Temperature on Thermal Conductivity

Inconel 718’s thermal conductivity varies with temperature. Generally, the thermal conductivity increases as the temperature rises. This property is crucial in applications involving heat transfer, such as jet engines and gas turbines.

Role of Different Fabrication Methods

The method of fabrication can significantly affect the properties of Inconel 718. Studies indicate that selective laser melting (SLM) provides highly compacted samples with high hardness values. However, spark plasma sintering (SPS) at 1000 °C exhibits higher thermal expansion.

Use in Various Industries

Thanks to its exceptional properties, Inconel 718 finds use in numerous industries. It’s commonly used in aerospace for manufacturing jet engines and high-speed airframe parts. It’s also employed in nuclear reactors, pumps, turbo pump seals, and tooling.

Further Research and Development

Researchers are continually exploring the thermal behavior of Inconel 718 to optimize its application in various industries. Recent studies focus on the effects of fabrication methods and heat treatment on the alloy’s thermal conductivity.


Inconel 718 exhibits excellent thermal conductivity, which varies with temperature. This property, combined with its high strength and corrosion resistance, makes it an ideal material for high-temperature applications. Ongoing research promises to further enhance our understanding of this versatile superalloy.

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