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 (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 for Alloy 800H/800HT®
|Melting Temperature||2475°F to 2525°F|
|Specific Heat, Btu/lb ˚F||0.11|
|Permeability @ 70°F for Annealed Material||1.014 (200 Oersted)|
|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|
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|