Alloy 800H/HT®
Description
Alloy 800H/800HT® are two individual solid solution strengthened, iron-nickel-chromium alloys typically offered as one, dual certified alloy meeting the chemical composition requirements of both alloys. The primary difference between Alloys 800H and 800HT® is the restricted aluminum and titanium content in 800HT®, which results in higher creep and stress rupture properties. Both Alloy 800H and 800HT® are generally considered to be superior to the base Alloy 800 (UNS N08800) because of greater creep and stress rupture properties and a more restrictive C wt% range.
With its high nickel and chromium content, Alloy 800H/800HT® provides excellent resistance to oxidation, carburization and sulfidation and is commonly used in applications that involve long-term exposure to high temperatures. Heat treatment and power generation are two common industries where Alloy 800 H/HT® is used with typical applications found in superheater and reheater tubing, headers, pigtails, outlet manifolds and sheathing for heating elements. Alloy 800H/800HT® also has excellent resistance to nitric acid at concentrations up to 70% and has good resistance to organic media like formic, acetic and propionic acids.
INCOLOY® and 800HT® are registered trademarks of Special Metals Corporation.
Chemical Composition
Chemical Composition (wt%)
| Iron | 39.5 min | Aluminum | 0.15 to 0.60 |
| Nickel | 30.0 to 35.0 | Titanium | 0.15 to 0.60 |
| Chromium | 19.0 to 23.0 | Carbon | 0.06 to 0.10 |
| Manganese | 1.5 max | Phosphorus | 0.045 max |
| Silicon | 1.0 max | Sulfur | 0.015 max |
| Copper | 0.75 max | Other | Al + Ti = 0.85 to 1.20 |
Physical Properties
Physical properties for Alloy 800H/800HT®
| Density, lb/in3 | 0.287 |
| Melting Temperature | 2475°F to 2525°F |
| Specific Heat, Btu/lb ˚F | 0.11 |
| Permeability @ 70°F for Annealed Material | 1.014 (200 Oersted) |
| Curie Temperature | -175°F |
| Elastic Modulus @ 75°F (Tension) | 28.50 X 103 ksi |
| Elastic Modulus @ 1600°F (Tension) | 19.20 X 103 ksi |
| Electrical Resistivity @ 70°F | 595 Ω•circ mil/ft |
| Electrical Resistivity @ 1800°F | 776 Ω•circ mil/ft |
Mechanical Properties
All properties in this table are for material in the solution annealed condition (hot worked and cold worked) and are from the governing ASTM specification.
| 0.2% Yield Strength, min. (ksi) | 25 |
| Tensile Strength, min. (ksi) | 65 |
| Elongation, min. (%) | 30 |