Incoloy 800HT, also known as “Alloy 800HT”, is designated as UNS N08811 or DIN W.Nr. 1.4959. It is an iron-nickel-chromium alloy having the same basic composition as Incoloy 800 and Incoloy 800H but with significantly higher creep-rupture strength. The higher strength results from deliberate control of the carbon, aluminum, and titanium contents in conjunction with a high-temperature anneal. Used in chemical and petroleum processing, in power plants for superheater and reheater tubing, in industrial furnaces, and for heat treating equipment.

Incoloy 800, 800H & 800HT have nearly identical chemical composition and physical properties. The major differences between these alloys are their mechanical properties which stem from the restricted compositions of alloys 800H and 800HT and the high-temperature anneals used for these alloys. In general, alloy 800 has higher mechanical properties at room temperature and during short-time exposure to elevated temperatures, whereas alloys 800H and 800HT have superior creep and rupture strength during extended high-temperature exposure.

1. Chemical Composition Requirements

The Chemical Composition of Incoloy 800, %
Nickel	30.0-35.0
Cromium	19.0-23.0
Iron	≥39.5
Carbon	0.06-0.10
Aluminum	0.25-0.60
Titanium	0.25-0.60
Manganese	≤1.50
Silicon	≤1.00
Sulfur	≤0.015
Copper	≤0.75
Al+Ti	0.85-1.20

2. Mechanical Properties of Incoloy 800HT

Tensile Strength, min.		Yield Strength, min.		Elongation, min.	Hardness, min.
Mpa	ksi	Mpa	ksi	%	HB
600	87	295	43	44	138

3. Physical Properties of Incoloy 800HT

Density	Melting Range		Specific Heat		Electrical Resistivity
g/cm3	°C	°F	J/kg. k	Btu/lb.°F	µΩ·m
7.94	1357-1385	2475-2525	460	0.110	989

4. Product Forms and Relative Standards

Product From	Standard
Rod and Bar	ASTM B408, EN 10095
Plate, Sheet & Strip	ASTM A240, A480, ASTM B409, B906
Seamless Pipe & Tube	ASTM B829, B407
Welded Pipe & Tube	ASTM B514, B515, B751, B775
Welded fittings	ASTM B366
Forging	ASTM B564, DIN 17460

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