What Is a Seamless Incoloy 800HT Pipe?
ASeamless Incoloy 800HT Pipe is a high-performance, nickel-iron-chromium superalloy piping solution engineered for long-term service in extreme thermal environments. Produced from a single solid billet, this seamless pipe eliminates the risk of weld-seam failure, ensuring maximum structural integrity under high-stress conditions.
The“800HT”(UNS N08811) designation represents the most advanced grade in the 800-series family. It is a dual-certified version of Incoloy 800H with precisely controlled levels of carbon, aluminum, and titanium. When combined with a high-temperature solution annealing heat treatment, 800HT delivers significantly higher creep and stress-rupture properties at temperatures above 1100°F(593°C) compared to standard 800 or 800H grades.
Key Features and Advantages
- Superior Creep-Rupture Strength: The strict control of Al + Ti content (0.85% -1.20%) ensures the highest design allowable stresses for long-term high-temperature service.
- Exceptional Oxidation & Carburization Resistance: High chromium content provides a protective oxide scale, while the nickel content maintains stability in carburizing atmospheres.
- Excellent Metallurgical Stability: Designed to resist embrittlement and maintain ductility even after thousands of hours of service in the 1200°Fto
1600°F range.
- Seamless Reliability: Uniform grain structure and wall thickness provide higher safety margins for high-pressure applications in furnaces and power plants.
- Field-Proven Weldability: Easily welded using matching composition filler metals (e.g., Inconel 82 or 617) with excellent resistance to hot cracking.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Incoloy 800HT.
The composition of Incoloy 800HT is carefully balanced to achieve its superior high-temperature strength and oxidation resistance.
Incoloy 800HT is specifically designed to maintain its strength and shape in high-stress, high-temperature environments.
These physical properties highlight the material’s ability to perform reliably under a wide range of conditions.
Cold-Finished Pipe and Tube:
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
| 0.500 to 5⁄8, excl. | ±0.005 | 12.7 to 15.8, excl. | ±0.127 |
| 5⁄8 to 1 1⁄2, incl. | ±0.0075 | 15.8 to 38.1, incl. | ±0.190 |
| Over 1 1⁄2 to 3 1⁄2, incl. | ±0.010 | Over 38.1 to 88.9, incl. | ±0.254 |
| Over 3 1⁄2 to 4 1⁄2, incl. | ±0.015 | Over 88.9 to 114.3, incl. | ±0.381 |
| Over 4 1⁄2 to 6, incl. | ±0.020 | Over 114.3 to 152.4, incl. | ±0.508 |
| Over 6 to 6 5⁄8, incl. | ±0.025 | Over 152.4 to 168.3, incl. | ±0.635 |
| Specified/Calculated Nominal OD (Inches) | Permissible Variation (Inches) | Specified/Calculated Nominal OD (mm) | Permissible Variation (mm) |
| 2 1⁄2 to 5 1⁄2, excl. | ±0.031 | 63.5 to 139.7, excl. | ±0.787 |
| 5 1⁄2 to 9 1⁄4, incl. | ±0.047 | 139.7 to 234.9, incl. | ±1.19 |
| Condition | Specified/Calculated Nominal OD (Inches) | Permissible Variation (Wall Thickness) |
| Cold-Finished | 0.500 to 5⁄8, excl. | ±15.0% |
| 5⁄8 to 4 1⁄2, incl. | ±10.0% | |
| Over 4 1⁄2 to 6 5⁄8, incl. | ±12.5% | |
| Hot-Finished | 2 1⁄2 to 9 1⁄4, incl. | ±12.5% |
Common Industrial Applications
The unique electrochemical profile of Nickel 200 seamless tubes makes them indispensable in several high-purity sectors:
Petrochemical Processing
Ethylene pyrolysis furnace tubes and convection sections.
Power Generation
Superheater and reheater tubing in advanced coal-fired and nuclear power plants.
Thermal Processing
Radiant tubes, retorts, and muffles for industrial heat-treating furnaces.
Hydrocarbon Processing
Components for steam/hydrocarbon reforming and pigtails.
Incoloy Series Comparison Reference:
| Grade | UNS Number | Primary Advantage |
| Incoloy 800 | N08800 | General corrosion and heat resistance. |
| Incoloy 800H | N08810 | Controlled carbon for improved creep strength. |
| Incoloy 800HT | N08811 | Optimized Al+Ti for maximum high-temp performance. |
| Incoloy 825 | N08825 | Superior resistance to sulfuric and phosphoric acids. |
Precision Manufacturing at Wenzhou Xinzhe Tech
AtWENZHOU XINZHE TECH CO., LTD., our 800HT seamless pipes undergo a rigorous multi-step process:
- Controlled Forging: Starting with high-purity billets with optimized chemistry.
- Precision Cold Working: Achieving exact tolerances per ASTM B407 Table 4 (Standard/Close tolerances).
- High-Temp Solution Annealing: Performed at a minimum of 2100°F (1150°C) to ensure grain size control (ASTM No. 5 or coarser), which is critical for creep strength.
- Non-Destructive Testing (NDT): 100% Eddy Current and Ultrasonic testing to verify subsurface integrity.
