If you’re looking for a material that excels in high-temperature environments and resists corrosion—whether for chemical reactors or nuclear components—UNS N08800 Incoloy 800 is a reliable choice. This nickel-iron-chromium alloy balances strength, heat resistance, and durability, making it a staple in tough industries. This guide breaks down its key properties, real-world uses, manufacturing methods, and how it compares to other materials—so you can make informed decisions for your projects.
1. Material Properties of UNS N08800 Incoloy 800
Incoloy 800’s performance stems from its carefully balanced composition and well-rounded characteristics. Let’s explore each property in detail.
1.1 Chemical Composition
Every element in this alloy works together to enhance heat resistance and corrosion protection. Below is its typical composition (by weight):
| Element | Content Range (%) | Key Role |
|---|---|---|
| Nickel (Ni) | 30–35 | Base metal—boosts high-temperature stability and resists stress cracking |
| Iron (Fe) | 39.5–46.5 | Adds structural strength and reduces overall material cost |
| Chromium (Cr) | 19–23 | Enhances oxidation resistance (critical for furnace and heat-treated parts) |
| Carbon (C) | Max 0.10 | Improves hardness while maintaining workability |
| Manganese (Mn) | Max 1.5 | Aids in manufacturing (e.g., welding and casting) |
| Silicon (Si) | Max 1.0 | Reduces oxidation at extreme temperatures |
| Sulfur (S) | Max 0.015 | Kept low to prevent brittleness and corrosion in harsh environments |
| Copper (Cu) | Max 0.75 | Boosts resistance to certain acids (e.g., sulfuric acid) |
| Titanium (Ti) | 0.15–0.60 | Prevents intergranular corrosion (common in high-heat applications) |
| Aluminum (Al) | 0.15–0.60 | Works with titanium to enhance oxidation resistance |
1.2 Physical Properties
These traits make Incoloy 800 easy to design with for high-temperature and industrial tasks:
- Density: 7.95 g/cm³ (lighter than Hastelloy alloys, similar to stainless steel)
- Melting Point: 1400–1450°C (2550–2640°F) – handles extreme heat in furnaces and reactors
- Thermal Conductivity: 15.1 W/(m·K) at 20°C (68°F); increases to 23.4 W/(m·K) at 600°C – efficient heat transfer
- Thermal Expansion Coefficient: 15.9 μm/(m·K) (20–100°C); 18.5 μm/(m·K) (20–600°C) – manageable expansion in high-heat cycles
- Electrical Resistivity: 105 Ω·mm²/m at 20°C – suitable for electrical components in high-temperature areas
- Magnetic Properties: Slightly magnetic at room temperature (becomes less magnetic at high temps) – works for most industrial needs
1.3 Mechanical Properties
Incoloy 800 maintains strength even at high temperatures, making it ideal for heat-intensive applications. All values below are for the annealed (heat-treated) version:
| Property | Value (Room Temperature) | Value at 600°C |
|---|---|---|
| Tensile Strength | Min 550 MPa (80 ksi) | 380 MPa (55 ksi) |
| Yield Strength | Min 240 MPa (35 ksi) | 220 MPa (32 ksi) |
| Elongation | Min 35% (in 50 mm) | 40% (in 50 mm) |
| Hardness | Max 180 HB (Brinell) | N/A |
| Fatigue Resistance | 220 MPa (10⁷ cycles) | 180 MPa (10⁷ cycles) |
| Creep Resistance | Maintains strength up to 870°C (1600°F) | – |
1.4 Other Properties
- Corrosion Resistance: Excellent in oxidizing environments (e.g., air, steam) and mild acids (e.g., dilute sulfuric acid) – outperforms carbon steel and many stainless steels.
- Oxidation Resistance: Resists scaling in air up to 980°C (1800°F) for long periods – ideal for furnace components.
- Stress Corrosion Cracking (SCC) Resistance: Resists SCC in chloride-rich environments (a common issue for 304 stainless steel).
- Pitting Resistance: Good resistance to pitting in salty or acidic brines (suitable for marine and chemical applications).
- Hot/Cold Working Properties: Easy to hot forge (at 1100–1200°C) and cold form (e.g., bending, stamping) – retains strength after shaping.
2. Applications of UNS N08800 Incoloy 800
Incoloy 800’s mix of high-temperature resistance and corrosion protection makes it perfect for demanding industries. Here are its most common uses, with real-world examples:
2.1 Heat Treatment Equipment
- Use Case: A metal processing plant in Germany uses Incoloy 800 for furnace heating elements. The elements withstand 850°C daily—they’ve lasted 5 years, compared to 2 years for stainless steel elements.
- Other Uses: Furnace liners, heat exchanger tubes, and annealing baskets.
2.2 Nuclear Industry
- Use Case: A nuclear power plant in France uses Incoloy 800 for steam generator tubes. The alloy resists corrosion from high-pressure steam and radioactive coolants, ensuring safety and reliability.
2.3 Chemical Processing Equipment
- Use Case: A chemical plant in the U.S. uses Incoloy 800 for sulfuric acid reactor vessels. The vessels operate at 400°C—they’ve run for 6 years without corrosion, compared to 3 years for carbon steel vessels.
- Other Uses: Acid storage tanks, pipework, and mixing tanks.
2.4 Oil and Gas Industry
- Use Case: An oil refinery in Saudi Arabia uses Incoloy 800 for catalytic cracker components. The alloy handles 700°C temperatures and resists hydrocarbon corrosion, cutting maintenance costs by 35%.
2.5 Aerospace Components
- Use Case: A European aerospace company uses Incoloy 800 for aircraft engine exhaust parts. The alloy’s high-temperature resistance ensures durability in jet engine heat (up to 800°C).
3. Manufacturing Techniques for UNS N08800 Incoloy 800
To maximize Incoloy 800’s performance, manufacturers rely on these proven methods:
- Casting: Sand casting and investment casting work well for complex shapes (e.g., furnace nozzles). The alloy’s low sulfur content prevents defects during casting.
- Forging: Hot forging (at 1100–1200°C) shapes the alloy into strong parts like pump impellers. Cold forging (at room temperature) is used for small components (e.g., bolts) to boost hardness.
- Welding: Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc Welding (SMAW) are recommended. Use matching filler metals (e.g., ERNiFeCr-2) to maintain corrosion resistance. Pre-weld cleaning (to remove oils) is critical for strong welds.
- Machining: Use high-speed steel (HSS) or carbide tools. Add coolant (e.g., soluble oil) to prevent overheating—Incoloy 800 can work-harden if cut too quickly.
- Heat Treatment:
- Annealing: Heat to 980–1050°C, cool rapidly (air or water) – softens the alloy for forming and restores ductility.
- Stress Relieving: Heat to 700–800°C, cool slowly – reduces internal stresses after welding or cold working.
- Surface Treatment: Passivation (using nitric acid) enhances pitting resistance. No painting is needed— the alloy’s natural surface resists rust in most environments.
4. Case Study: Incoloy 800 in a Heat Treatment Furnace
A car manufacturing plant in Japan needed to upgrade its heat treatment furnace. The old furnace used stainless steel (310S) for its heating chamber, which failed after 3 years due to oxidation at 900°C.
They switched to an Incoloy 800 chamber. Here’s the outcome:
- Lifespan: The chamber has operated for 7 years with no signs of oxidation.
- Cost Savings: Maintenance costs dropped by 50% (no need for frequent chamber replacements).
- Performance: The alloy’s even heat distribution improved the quality of heat-treated car parts—defect rates fell by 15%.
This case proves why Incoloy 800 is the top choice for high-temperature heat treatment equipment.
5. Comparative with Other Materials
How does UNS N08800 Incoloy 800 stack up against other common materials? The table below compares key properties:
| Material | Max Service Temp (°C) | Corrosion Resistance (Oxidizing Env.) | Tensile Strength (MPa) | Cost (Relative) |
|---|---|---|---|---|
| Incoloy 800 | 870 | Excellent | 550 | Medium-High |
| Stainless Steel 316 | 870 | Good | 515 | Low |
| Titanium Alloy Ti-6Al-4V | 400 | Very Good | 860 | Very High |
| Inconel 625 | 980 | Excellent | 930 | High |
| Hastelloy C22 | 650 | Excellent | 690 | High |
| Monel 400 | 480 | Good (seawater) | 550 | Medium |
| Carbon Steel | 425 | Poor | 400 | Very Low |
Key Takeaways:
- Incoloy 800 outperforms stainless steel in oxidation resistance at high temperatures.
- It’s more affordable than titanium alloys and Inconel, making it a cost-effective choice for heat-intensive tasks.
- Inconel 625 works better at extreme temps, but Incoloy 800 offers better value for applications up to 870°C.
Yigu Technology’s Perspective
At Yigu Technology, we recommend UNS N08800 Incoloy 800 for clients in heat treatment, nuclear, and chemical industries. Its exceptional high-temperature resistance and corrosion protection make it a reliable, long-lasting solution. Our team provides custom machining and heat treatment for Incoloy 800 components, ensuring they meet strict industry standards. For projects needing strength in oxidizing or high-heat environments, Incoloy 800 delivers unmatched value.
FAQ
1. Can UNS N08800 Incoloy 800 be used in nuclear applications?
Yes! It’s commonly used for nuclear steam generator tubes and reactor components. Its resistance to high-pressure steam and radioactive coolants meets strict nuclear safety standards, making it a trusted choice.
2. Is Incoloy 800 suitable for marine environments?
Absolutely. Its good pitting resistance and corrosion protection in salty water make it ideal for marine parts like heat exchangers and offshore equipment—outperforming carbon steel and brass.
3. What’s the typical lifespan of Incoloy 800 parts in high-temperature applications?
In heat-intensive tasks (e.g., furnace components, steam generators), Incoloy 800 parts last 5–10 years—2–3 times longer than stainless steel parts. Proper maintenance (e.g., annealing) can extend this lifespan even further.
