Alloy 800H/800HT （UNS N08810&NO8811） | |||||||||
Summary | Nickel-iron-chromium alloys having the same basic composition as alloy 800 but with significantly higher creep-rupture strength. The higher strength results from close control of the carbon, aluminum, and titanium contents in conjunction with a high-temperature anneal. Used in chemical and petrochemical processing, in power plants for super-heater and reheater tubing, in industrial furnaces, and for heat-treating equipment. | ||||||||
Standard Product Forms | Pipe, tube, sheet, strip, plate, round bar, flat bar, forging stock, hexagon and wire. | ||||||||
Chemical Composition Wt,% |
| Min | Max. |
| Min. | Max. |
| Min. | Max. |
Ni | 30.0 | 35.0 | Al800H | 0.15 | 0.6 |
|
|
| |
Cr | 19.0 | 23.0 | Al800HT | 0.15 | 0.6 | Al+Ti800HT | 0.85 | 1.2 | |
Fe | 39.5 |
| Ti800H | 0.15 | 0.6 | Si |
| 1.0 | |
C800H | 0.05 | 0.1 | Ti800HT | 0.15 | 0.6 | S |
| 0.015 | |
C800HT | 0.06 | 0.1 | Mn |
| 1.5 | Cu |
| 0.75 | |
Physical Constants | Density,g/ | ||||||||
Melting Range,℃ 357-1385 | |||||||||
Typical Mechanical Properties | (Annealed) (1000h) Rupture Strength (1000h) ksi Mpa 1200℉/650℃ 24 165 1300℉/705℃ 15 105 1400℉/760℃ 10 70 1600℉/870℃ 4.7 32 1800℉/980℃ 2 14 | ||||||||
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7.94
Microstructure
Alloy 800H and 800HT, as the same to the Incoloy 800, are also sustenitic, solidsolution alloys. Titanium nitride, titanium carbides, and chromium carbides normally appear in the alloys' microstruture.
Characters
Alloy 800H is characterized by:
Good creep-rupture properties at temperature above 600℃(1110℉) without loss of ductility during long-term use at temperatures below 700℃(℉), due to limitation of (Ti+Al) content to max. 0.7%;
Good resistance to reducing, oxidizing and nitriding atmospheres and to atmospheres which alternate between reducing and oxidizing conditions;
Metallurgical stability in long-term application at high temperature.
Alloy 800HT is characterized:
Excellent creep strength at temperature above 700℃. However, for application where frequent excursions to temperatures lower than 700℃ during service cannot be excluded or parts of the material are permanently exposed to a temperature below 700℃, the use of Incoloy 800H is recommended.
Good resistance to reducing, oxidizing and nitriding atmospheres and to atmospheres which alternate between reducing and oxidizing conditions;
Metallurgical stability in long-term application at high temperature.
Corrosion Resistance
Alloy 800, 800H and 800HT have the same nickel, chromium, and iron contents and generally display similar corrosion resistance. The high nickel and chromium contents of Incoloy 800H, 800HT and 800 ensure excellent resistance to oxidation. Compared to Alloy 800, the 800H and 800HT can be used at higher temperature and still have a good strength, the alloys are also very resistant to carburization, nitridation sulphur-bearing atmospheres at high temperature. Resistance to hydrogen is excellent for Incoloy 800H and 800HT.
Applications
Alloy 800H and Alloy 800HT for more than
1. Steam/hydrocarbon reforing for components such as: transfer piping, catalyst (in lowpressure processes) and quench-system piping;
2. Cracking tubes used in the production of acetic anhydride and ketene-high strength, resistance to carburization and to dry hydrogen chloride and chlorine;
3. Components, e.g. Heat exchangers, piping system etc., in coal conversion plants.