If you’ve ever worked in aerospace, chemical processing, or power generation—industries that demand materials that can stand up to extreme heat, corrosion, and mechanical stress—you’ve likely encountered Inconel Alloy. As a supplier who’s spent 12 years navigating the ins and outs of superalloys, one of the most common questions I get from engineers and procurement teams isn’t just “What is Inconel?” It’s, “What’s its thermal conductivity, and why does it matter for my application?” Inconel Alloy
Let me start with a quick, honest truth: thermal conductivity isn’t a one-size-fits-all number for Inconel. It shifts based on which specific Inconel grade you’re using, the temperature it’s operating at, and even how it’s processed. That flexibility is part of what makes Inconel so valuable, but it’s also what leads to a lot of confusion. Back when I first started in this business, a client once ordered a batch of Inconel 718 tubes for a gas turbine heat exchanger, only to find that their calculations for heat transfer didn’t line up with our material data. The issue? They used a room-temperature thermal conductivity number for Inconel 625 instead of verifying the grade they’d specified. That mistake taught me early on: context is everything when it comes to thermal properties.
First, let’s break down what thermal conductivity actually means. For anyone who’s not a materials engineer, think of it as a material’s ability to conduct heat—measured in watts per meter-kelvin (W/m·K). The higher the number, the faster heat moves through the material. For superalloys like Inconel, this property is critical. In heat exchangers, for example, you want heat to transfer efficiently from one fluid to another, so a moderate, consistent thermal conductivity is key. In other applications, like exhaust manifolds or high-temperature fasteners, you might want Inconel to resist heat spread—meaning lower thermal conductivity is an advantage. It all comes down to the use case.
Now, let’s get into the numbers, starting with the most popular Inconel grades. The two workhorses in our inventory are Inconel 625 and Inconel 718, and their thermal conductivities don’t behave the same way as temperature rises. At room temperature (20°C, or 68°F), Inconel 625 has a thermal conductivity of about 9.8 W/m·K. That’s low compared to, say, stainless steel (which clocks in around 16 W/m·K at room temp) or aluminum (around 205 W/m·K). But here’s the thing: as temperature goes up, Inconel 625’s thermal conductivity increases. At 500°C (932°F), it jumps to roughly 22 W/m·K, and at 800°C (1472°F)—a common operating temp for jet engine components—it’s around 28 W/m·K. That upward trend continues, but much more gradually, as temperatures climb higher, topping out around 35 W/m·K at 1100°C (2012°F).
Inconel 718, the grade most often used for structural parts in turbines and nuclear reactors, has a slightly different profile. At room temperature, its thermal conductivity is a touch lower than 625—around 11.6 W/m·K. It also rises with temperature, but at a slower rate. At 500°C, it’s about 19 W/m·K, and at 800°C, it’s roughly 26 W/m·K. This difference might seem small on paper, but for a component that operates at sustained high temperatures, it can shift how you design for heat expansion and stress. For example, a turbine blade made of 718 won’t spread heat as quickly as one made of 625 at the same temperature, which means less risk of thermal fatigue in high-stress areas.
You’ll also hear mention of less common Inconel grades, like Inconel X-750, used for springs and fasteners that need to retain strength at extreme heat. Its thermal conductivity at room temperature is around 10.4 W/m·K, similar to 625, and it rises to about 25 W/m·K at 800°C. Then there’s Inconel 600, the original Inconel grade developed in the 1940s, which has a higher thermal conductivity overall—around 14.7 W/m·K at room temp, climbing to 30 W/m·K at 800°C. That’s why 600 is often chosen for applications where a bit more heat transfer is helpful, like furnace fixtures, even if its strength lags behind newer grades at very high temperatures.
Why does this variation exist between grades? Inconel is a nickel-chromium superalloy, but the small alloying additions—things like molybdenum, niobium, iron, or titanium—are what tweak its properties. Inconel 625, for example, has a high molybdenum and niobium content that boosts its corrosion resistance, but those elements also impact electron movement, which is how heat is conducted through metals. More alloying elements mean more obstacles for electrons, so lower thermal conductivity at a given temperature. Inconel 718’s higher iron content, on the other hand, slightly increases its ability to conduct heat compared to 625, even with similar alloying levels. Processing also plays a role: a forged Inconel part vs. a welded one, or one that’s been heat-treated, can have microstructural differences that shift thermal conductivity by 5-10% in some cases. That’s why, as a supplier, we always provide material test reports (MTRs) with thermal conductivity values specific to every batch we ship—no generic numbers, just real data for your exact part.
Let’s talk about real-world applications to put this into context. Last year, a team from a power plant in the Midwest reached out to us because their old Inconel 600 heat exchanger tubes were failing at 650°C. They’d been using the generic room-temperature thermal conductivity number for Inconel to calculate heat transfer, which led them to design the exchanger with too few tubes. When they switched to Inconel 625, they adjusted their calculations using our MTR data (24 W/m·K at 650°C) and added 20% more tube surface area. That fixed the overheating issue, and the exchanger has been running without problems for 18 months now. Another client, a aerospace manufacturer, needed fasteners for a jet engine afterburner that couldn’t spread heat into adjacent composite parts. They chose Inconel X-750, whose lower thermal conductivity (22 W/m·K at 700°C) helped keep the fastener’s heat localized, preventing thermal damage to the composites.
A common misconception is that higher thermal conductivity is always better. In reality, it depends on whether you’re managing heat transfer or heat retention. For applications where you need to dissipate heat—like a heat sink for a high-performance electronics component—you might pair Inconel’s strength with a high-thermal-conductivity grade. For applications where you need to insulate against extreme heat (short-term, not long-term), lower thermal conductivity is a plus, as it slows heat penetration into the material. It’s also worth noting that at temperatures above 1000°C, thermal conductivity in Inconel starts to decrease slightly for all grades, as radiation becomes the main mode of heat transfer rather than electron movement. That’s why, for ultra-high-temperature applications (like metal cutting tools operating above 1200°C), engineers often adjust their design to account for this shift in heat transfer behavior.
As a supplier, I’ve seen too many projects go off the rails because someone grabbed a generic thermal conductivity number off the internet without verifying the grade and temperature. That’s why we make it a point to walk through these details with every client. When you order Inconel from us, we don’t just send a box of parts—we provide a complete data sheet that includes not just thermal conductivity, but tensile strength, corrosion resistance, and even how the material will perform at the exact temperature you specified. If you’re not sure which grade is right for your application, we’ll work with your engineering team to break down the tradeoffs: do you need higher strength, better corrosion resistance, or a specific thermal conductivity profile?
If you’re working on a project that relies on Inconel’s thermal properties—whether it’s a heat exchanger, a turbine component, a chemical processing vessel, or something else entirely—don’t rely on generic data. Reach out to our team to discuss your needs. We can provide custom material test reports, help you select the right grade for your operating temperature, and even offer guidance on how Inconel’s thermal behavior will impact your design.
ASTM Carbon Steel Pipe References:
- Davis, J.R. (Ed.). (1997). Nickel, Cobalt, and Their Alloys. ASM International.
- NASA. (2004). Material Properties Data for Superalloys Used in Aerospace Propulsion Systems. NASA Technical Publication TP-2004-212875.
- Inconel Alloy Technical Data Sheets. Special Metals Corporation. (2022).
- Pollock, T.M. (2010). “Superalloys for High-Temperature Applications.” Annual Review of Materials Research, 40, 503-529.
- American Society of Mechanical Engineers (ASME). (2021). Boiler and Pressure Vessel Code, Section II: Material Properties. ASME International.
Jiangsu Xurui Metal Group Co., Ltd.
With abundant experience, we are one of the most professional inconel alloy manufacturers and suppliers in China. We are committed to providing high quality metal products for global clients. Please feel free to wholesale bulk high-grade inconel alloy in stock here from our factory.
Address: 32-117, South Stainless Steel Market, Xinwu District, Wuxi, Jiangsu, China
E-mail: Mia@xuruimetal.com
WebSite: https://www.xurui-steel.com/
