Composition and Basic Properties
Incoloy 800:
Incoloy 800 is a nickel-iron-chromium alloy with additions of aluminum and titanium. The composition typically includes:
- Nickel (Ni): 30-35%
- Chromium (Cr): 19-23%
- Iron (Fe): 39.5% minimum
- Aluminum (Al): 0.15-0.60%
- Titanium (Ti): 0.15-0.60%
- Carbon (C): 0.1% maximum
Incoloy 800 is known for its excellent strength and resistance to oxidation, carburization, and nitridation at elevated temperatures. It retains its strength even at high temperatures and is often used in applications where thermal cycling and resistance to sulfidation are critical.
Inconel 800:
Inconel 800 is technically not a specific alloy designation; rather, it is more commonly referred to as Inconel 800 series alloys, particularly Inconel 800H and Inconel 800HT. These alloys have similar compositions and properties but are slightly modified for different applications:
- Nickel (Ni): 30-35%
- Chromium (Cr): 19-23%
- Iron (Fe): 39.5% minimum
- Aluminum (Al): 0.15-0.60%
- Titanium (Ti): 0.15-0.60%
- Carbon (C): 0.05-0.1% (Inconel 800H) or 0.06-0.10% (Inconel 800HT)
Inconel 800H has higher carbon content, which provides enhanced creep-rupture strength at temperatures above 1100°F (593°C). Inconel 800HT offers further improvements in creep and stress rupture properties.
Mechanical Properties
The mechanical properties of both alloys are crucial in determining their performance in various applications:
| Property | Incoloy 800 | Inconel 800H | Inconel 800HT |
|---|---|---|---|
| Tensile Strength (MPa) | 520-690 | 600-800 | 600-800 |
| Yield Strength (MPa) | 210-550 | 275-420 | 275-420 |
| Elongation (%) | 30 (minimum) | 30 (minimum) | 30 (minimum) |
| Hardness (HRC) | 30-35 | 30-35 | 30-35 |
Thermal Properties
Both alloys exhibit excellent thermal stability and resistance to thermal cycling, making them suitable for applications involving high temperatures:
- Maximum Service Temperature: Up to 1100°C (2000°F) for Incoloy 800 and Inconel 800 series alloys.
- Thermal Expansion: Similar coefficients of thermal expansion, ensuring dimensional stability under varying temperature conditions.
Corrosion Resistance
Both Incoloy 800 and Inconel 800 series alloys offer outstanding resistance to oxidation and carburization in high-temperature environments. Their high nickel content forms a protective oxide layer, which enhances their resistance to corrosion.
Applications
Incoloy 800: Commonly used in applications such as:
- Industrial furnaces
- Petrochemical processing
- Heat-treating equipment
- Power generation plants
Inconel 800 series (800H and 800HT):
- Inconel 800H: Used in applications requiring high creep-rupture strength at elevated temperatures.
- Inconel 800HT: Used in applications requiring further enhanced creep and stress rupture properties.
Weldability and Fabrication
Both alloys are readily weldable using conventional welding techniques. They can be fabricated into various forms such as plates, sheets, bars, and pipes, making them versatile for different manufacturing processes.
Cost Considerations
In general, Incoloy 800 and Inconel 800 series alloys are premium alloys due to their nickel content and specialized properties. The cost may vary based on the specific grade and form required for a particular application.
Conclusion
Incoloy 800 and Inconel 800 series alloys, despite their subtle compositional differences, exhibit comparable performance in high-temperature and corrosive environments. The choice between these alloys often depends on specific application requirements, such as temperature range, mechanical properties, and resistance to oxidation and corrosion.
Both alloys have a proven track record in industries requiring reliable performance under extreme conditions, making them preferred choices for critical components in petrochemical, aerospace, power generation, and heat-treating applications.
In summary, while Incoloy 800 and Inconel 800 series alloys share many similarities in composition and performance, the slight variations in carbon content and subsequent mechanical properties allow them to cater to different needs within high-temperature environments. Therefore, the selection between Incoloy 800 and Inconel 800 series alloys should be based on detailed consideration of specific application requirements and performance criteria.