ASTM B407 Incoloy 800 Tube vs Inconel 600: Key Differences in Industrial Use

The Alloys at a Glance: What Are Incoloy 800 and Inconel 600?

Before diving into their differences, let's ground ourselves in the basics. Both Incoloy 800 and Inconel 600 are nickel-chromium-iron alloys, born from the need to withstand harsh environments where standard steel would fail. But their recipes? That's where the first split happens.

Incoloy 800 , defined by ASTM B407 (a specification for nickel-iron-chromium alloy seamless tubes), leans into iron. Typically, it contains 30-35% nickel, 19-23% chromium, and a hefty 39-47% iron, with small additions of aluminum and titanium. This iron-rich composition gives it a unique balance of strength and versatility, especially in high-temperature settings.

Inconel 600 , on the other hand, is a nickel-dominant alloy (72% nickel, 14-17% chromium, 6-10% iron). No aluminum or titanium here—just a straightforward, robust mix designed for uncompromising corrosion resistance and thermal stability. It's the kind of alloy that thrives when the going gets tough, whether that's saltwater, acids, or extreme heat.

Think of them as two expert athletes: one built for endurance in varied terrain (Incoloy 800), the other for raw power in specialized conditions (Inconel 600). Their differences start in the lab, but they play out in real-world applications that keep industries running.

Composition Matters: How Alloys Shape Performance

The elements in an alloy are like ingredients in a recipe—swap one, and the whole dish changes. Let's break down what each component brings to the table, and how Incoloy 800 and Inconel 600's unique mixes set them apart.

Nickel, the star of both shows, is the reason these alloys resist corrosion and maintain strength at high temperatures. But Inconel 600's higher nickel content (72% vs. Incoloy 800's 30-35%) gives it an edge in environments where reducing agents (like hydrogen) are present. It's like adding an extra layer of armor against chemical attacks.

Chromium, the unsung hero, forms a thin, protective oxide layer on the alloy's surface, shielding it from oxidation (rust) and scaling at high heat. Both alloys have similar chromium levels (around 20%), but Incoloy 800's aluminum and titanium additions supercharge this oxide layer, making it more stable in cyclic temperature changes—think of a power plant's heat exchanger tube that heats up and cools down daily. Inconel 600, without these additives, relies purely on its nickel-chromium backbone, which holds strong in steady, extreme conditions but can be prone to oxide spalling (flaking) if temperatures swing wildly.

Iron, Incoloy 800's secret weapon, brings affordability and workability. More iron means lower raw material costs, and it makes the alloy easier to form into complex shapes—critical for custom applications like U bend tubes or finned tubes used in heat exchangers. Inconel 600's lower iron content makes it pricier and trickier to machine, but that trade-off buys unmatched resistance to chloride stress corrosion cracking—a common killer in marine environments.

Mechanical Muscle: Strength, Ductility, and Pressure Handling

In industrial settings, tubes don't just sit there—they're squeezed, stretched, and hammered by pressure, weight, and vibration. Let's talk numbers: how much can these alloys take before they bend, break, or fail?

Tensile strength (the maximum stress a material can handle before breaking) tells part of the story. Incoloy 800 clocks in at around 550-690 MPa, while Inconel 600 hits 655-827 MPa. On paper, Inconel 600 is stronger, but here's the catch: Incoloy 800 retains more of that strength at high temperatures. At 800°C (1472°F), Incoloy 800's tensile strength drops to about 200 MPa, while Inconel 600's falls to 150 MPa. For power plants & aerospace applications—where components operate near 1000°C—this difference can make or break a system's lifespan.

Yield strength (the stress at which a material starts to deform permanently) is another key metric. Inconel 600 edges out here too, with a yield strength of 240-415 MPa vs. Incoloy 800's 170-310 MPa. This makes Inconel 600 a better choice for structural works or pressure tubes where rigidity is non-negotiable, like in nuclear reactors or high-pressure pipeline works.

But strength isn't everything. Ductility—the ability to bend without breaking—matters for fabrication. Incoloy 800, with its higher iron content, has better ductility (30-40% elongation) than Inconel 600 (25-30%). This means it can be cold-worked into tight bends (hello, U bend tubes) or welded into complex assemblies without cracking. For custom projects where standard tube sizes won't cut it, this flexibility is a game-changer. Inconel 600, while less ductile, makes up for it in toughness—its ability to absorb energy without fracturing, which is why it's a staple in marine & ship-building where impacts from waves or cargo are par for the course.

Corrosion Resistance: Who Fights Off the Bad Guys?

If mechanical strength is a tube's muscles, corrosion resistance is its immune system. Industries like petrochemical facilities , marine, and wastewater treatment throw some of the nastiest attackers at metal: acids, salts, chlorides, and sulfur compounds. Let's see how our alloys stack up.

Oxidizing environments (think high oxygen, like boiler systems): Both alloys shine here, thanks to their chromium content. Incoloy 800's aluminum-titanium boost makes it slightly better at resisting scaling (the buildup of oxide layers) in cyclic settings, like a boiler that fires up and shuts down regularly. Inconel 600, though, holds its own in continuous high-oxygen environments—say, a power plant's superheater tubes that run hot 24/7.

Reducing environments (low oxygen, like hydrogen-rich petrochemical processes): Inconel 600's high nickel content is a lifesaver here. Nickel loves hydrogen, forming a stable bond that prevents hydrogen embrittlement (a catastrophic weakening of the metal). Incoloy 800, with less nickel, can struggle in hydrogen-sulfide-rich environments—common in oil refineries—unless it's specially heat-treated. That's why many petrochemical projects opt for Inconel 600 in heat exchanger tubes handling sour crude.

Marine and saltwater: Chlorides are the enemy here, and Inconel 600 is the heavyweight champion. Its low iron content and high nickel make it nearly impervious to chloride stress corrosion cracking, a silent killer that can split tubes open in saltwater cooling systems. Incoloy 800, while decent in freshwater, can develop pitting or cracks in seawater unless coated or paired with corrosion inhibitors. That's why shipbuilders reach for Inconel 600 when fabricating steel tubular piles or seawater intake pipes.

Acids and alkalis: Inconel 600 takes the lead in strong acids like sulfuric or nitric acid, where its nickel-chromium mix forms a protective barrier. Incoloy 800, though, holds its own in weaker acids and alkalis, making it a cost-effective choice for chemical processing plants that don't deal with ultra-strong reagents.

Thermal Stability: When the Heat Turns Up

Power plants, aerospace engines, and industrial furnaces don't just get hot—they get extremely hot. We're talking 1000°C (1832°F) and beyond. At these temperatures, metals start to creep (slowly deform under stress) or melt. How do Incoloy 800 and Inconel 600 hold up?

Incoloy 800 is a rockstar in moderate to high heat with temperature fluctuations. Its aluminum and titanium additions form tiny, stable precipitates (like Ni3Al) that pin the grain boundaries of the metal, slowing creep. This makes it ideal for heat efficiency tubes in power plants, where steam temperatures rise and fall as demand spikes. It can handle continuous use up to 870°C (1600°F) and short bursts up to 1000°C.

Inconel 600, though, thrives in steady extreme heat. Without those aluminum-titanium precipitates, it creeps more at lower temperatures than Incoloy 800, but once the mercury climbs past 900°C, its high nickel content keeps it stable. This makes it the go-to for aerospace applications, like jet engine exhaust components, where temperatures stay consistently scorching. It's also a staple in nuclear facilities, where its resistance to radiation-induced embrittlement (thanks to low cobalt content) is critical for RCC-M Section II nuclear tubes .

Industrial Applications: Where Do They Actually Work?

Theory is great, but let's get practical. Where do these alloys earn their keep in the real world?

Power Plants: Incoloy 800 stars in heat exchanger tubes and boiler tubing, where its cyclic temperature resistance and affordability shine. Inconel 600, meanwhile, handles the superheater and reheater sections, where steady high heat and pressure demand its brute strength.

Marine & Ship-Building: Inconel 600 is king here. Its chloride resistance makes it perfect for seawater cooling systems, propeller shafts, and steel tubular piles driven into saltwater-saturated soil. Incoloy 800 might pop up in freshwater ballast tanks or non-critical components, but it can't compete with Inconel's saltwater stamina.

Petrochemical Facilities: It's a toss-up. Inconel 600 dominates hydrogen-rich processes (like hydrocracking units) and sour crude handling, where sulfide corrosion is a risk. Incoloy 800, cheaper and easier to form, takes over in custom condenser tubes or finned tubes for distillation columns, where temperatures cycle and corrosion isn't as aggressive.

Aerospace: Inconel 600's high-temperature stability makes it a favorite for exhaust systems and turbine blades. Incoloy 800, with its better workability, sometimes appears in less extreme parts like fuel lines or heat shields, but it can't match Inconel's performance at the edge of space.

Custom and Specialty Projects: When engineers need tubes bent into tight U-shapes, finned for extra heat transfer, or welded into complex assemblies, Incoloy 800 is often the call. Its ductility and formability make it a dream for custom alloy steel tube shops. Inconel 600, while possible to custom-fabricate, requires specialized tooling and expertise—adding time and cost to projects.

The Verdict: How to Choose?

At the end of the day, there's no "better" alloy—only the right one for your project. Here's a quick cheat sheet:

• Choose Incoloy 800 if you need affordability, workability, or cyclic high-temperature resistance—think power plant heat exchangers, custom U bend tubes, or freshwater industrial systems.
• Choose Inconel 600 if you're facing saltwater, hydrogen-rich environments, or steady extreme heat—like marine tubular piles, petrochemical sour crude lines, or aerospace components.
• When in doubt, ask: What's the biggest threat to my tubes? Corrosion? Heat? Cost? Let that threat guide your choice.

Side-by-Side Comparison

Final Thoughts: Beyond the Alloy

At the end of the day, the success of any industrial tube project depends on more than just the alloy—it's about partnering with suppliers who understand your needs, whether you're buying wholesale stainless steel tube for a large pipeline or a one-off custom condenser tube for a prototype. Incoloy 800 and Inconel 600 are tools in your toolkit; the best engineers know when to reach for each. So next time you're staring at a spec sheet, remember: these tubes aren't just metal—they're the backbone of the world we build. Choose wisely.