1. What is the main difference between Inconel 800, 800H, and 800HT?
Answer:
Inconel 800: Standard grade, suitable for general high-temperature applications.
Inconel 800H: Has higher carbon content (0.05–0.10%) to improve creep resistance and strength at elevated temperatures, typically up to 1100°F (593°C).
Inconel 800HT: Heat-treated version of 800H, with solution annealing to enhance thermal stability and resistance to oxidation, suitable for temperatures up to 1200°F (649°C).
2. What are the common applications for Inconel 800 series seamless tubes?
Answer:
Heat exchangers and furnace components in chemical and petrochemical industries
Gas turbines and power generation equipment
Nuclear reactors and steam generator tubing
Exhaust systems in high-temperature environments
The material is preferred for applications requiring high strength, oxidation resistance, and thermal stability.
3. What are the mechanical properties of Inconel 800/800H/800HT tubes?
Answer:
Tensile Strength (MPa): 450–550 (800), 490–620 (800H/HT)
Yield Strength (MPa): 205–275 (800), 275–345 (800H/HT)
Elongation (%): 30–40 (all grades)
Hardness (HRB): 70–90
These properties may vary depending on heat treatment and tube dimensions, but the alloy consistently maintains high strength at elevated temperatures.
4. What are the chemical compositions of Inconel 800 series?
Answer:
| Element | UNS N08800 (800) | UNS N08810 (800H) | UNS N08811 (800HT) |
|---|---|---|---|
| Nickel (Ni) | 30–35% | 30–35% | 30–35% |
| Chromium (Cr) | 19–23% | 19–23% | 19–23% |
| Iron (Fe) | Balance | Balance | Balance |
| Carbon (C) | 0.10% max | 0.05–0.10% | 0.05–0.10% |
| Manganese (Mn) | 1% max | 1% max | 1% max |
| Silicon (Si) | 1% max | 1% max | 1% max |
| The key differences are mainly in carbon content and controlled heat treatment. |
5. What are the corrosion resistance characteristics of these alloys?
Answer:
Excellent resistance to oxidation and carburization at high temperatures
Resistant to aqueous corrosion in neutral and mildly oxidizing environments
Performs well in sulfur-containing atmospheres due to chromium content
Not recommended for strong reducing acids (e.g., hydrochloric acid) or halide-rich environments
Inconel 800 series tubes maintain structural integrity and corrosion resistance in both high-temperature and chemical environments.
