Incoloy 800, 800H, and 800HT are nickel-iron-chromium alloys having high resistance to carburization and oxidation in high-temperature exposure and with good strength. These nickel steel alloys are identical except for the higher level of carbon in alloy 800H, and the addition of up to 1.20 % aluminum and titanium in alloy 800HT.
Incoloy 800 was the first of these alloys and it was slightly modified into Incoloy 800H. The modification made was to control carbon (.05-.10%) and grain size to optimize stress rupture properties. Incoloy 800HT has more modifications to the combined aluminum and titanium levels (.85-1.20%) to ensure optimum high temperature properties.
The nickel alloy is dual certified (800H/HT) and combines the properties of both forms. Incoloy 800H/HT alloy was actually meant for high-temperature structural applications. These alloys are resistant to embrittlement from precipitation of sigma phase and chloride stress-corrosion cracking due to the nickel content. The corrosion resistance is quite high.
In the solution annealed condition, alloys 800H and 800HT have excellent creep and stress rupture properties. The dual certified 800H/HT alloy is commonly available also with Yaang Pipe Industry.
Incoloy 800 is mainly used in applications with temperatures up to 1100° F, where alloys 800H and 800HT are normally used in temperatures above 1100° F where resistance to creep and rupture is required. The chemical balance allows the nickel steel alloy to exhibit excellent resistance to carburization, oxidation and nitriding atmospheres.
Incoloy 800HT will not become embrittled even after long periods of usage in the 1200-1600° F range where many stainless steels become brittle.
Superior cold forming properties associated with the nickel-chromium alloys are exhibited with 800HT. When cold forms extensively, the grain size produces a visibly undulated surface called “orange peel”. Incoloy 800HT can be welded by the common techniques used on stainless steels.
Chemical Composition
Alloy 800 (UNS N08800) Chemical Composition, %
The chemical composition of Alloy 800 is:
| Ni | Fe | Cr | Cu | Ti | Al | C | Mn | S | Si |
|---|---|---|---|---|---|---|---|---|---|
| 30.0-35.0 | 39.5 min | 19.0-23.0 | .75 max | .15-.60 | .15-.60 | .1 max | 1.5 max | .015 max | 1.0 max |
Alloy 800H (UNS N08810) Chemical Composition, %
The chemical composition of alloy 800H is:
| Ni | Fe | Cr | Cu | Ti | Al | C | Mn | S | Si |
|---|---|---|---|---|---|---|---|---|---|
| 30.0-35.0 | 39.5 min | 19.0-23.0 | .75 max | .15-.60 | .15-.60 | .05-.10 max | 1.5 max | .015 max | 1.0 max |
Alloy 800HT (UNS N08811) Chemical Composition, %
The chemical composition of Alloy 800HT is :
| Ni | Fe | Cr | Cu | Ti | Al | C | Mn | S | Si |
|---|---|---|---|---|---|---|---|---|---|
| 30.0-35.0 | 39.5 min | 19.0-23.0 | .75 max | .25-.60 | .85-1.20 | .06-.10 max | 1.5 max | .015 max | 1.0 max |
Forms of INCOLOY 800/800H/800HT
The forms of INCOLOY 800/800H/800HT are:
- flange (for example:Incoloy 800 adapter flange)
- Plate
- Bar
- Pipe & Tube (welded & seamless)
- Fittings (i.e., flanges, slip-ons, blinds, weld-necks, lap joints, long welding necks, socket welds, elbows, tees, stub-ends, returns, caps, crosses, reducers, and pipe nipples)
- Wire.
Properties of INCOLOY 800H/800Ht
The properties of 800H/800Ht are:
- High temperature strength
- Good resistance to many sulfur-containing atmospheres
- High creep rupture strength
- Resistant to carburization and oxidation in high temperature environments
- Good corrosion resistance in many acidic environments.
Mechanical Properties (Typical room temperature Tensile Properties of Annealed Material)
The mechanical properties of INCOLOY 800H/HT are:
| Product | Tensile (ksi) | .2% Yield (ksi) | Elongation (%) |
|---|---|---|---|
| Rod & Bar | 75-100 | 30-60 | 60-30 |
ASTM Specifications
The ASTM specifications are:
| Alloy | Pipe Smls | Pipe Welded | Tube Smls | Tube Welded | Sheet/Plate | Bar | Forging | Fitting |
|---|---|---|---|---|---|---|---|---|
| Alloy 800 (UNS N08800) | B407 | B154 | B163 | B515 | B409 | B408 | B564 | B366 |
| Alloy 800H (UNS N08810) | B407 | B154 | B163 | B515 | B409 | B408 | B564 | B366 |
| Alloy 800HT (UNS N08811) | B407 | B154 | B163 | B515 | B409 | B408 | B564 | B366 |
Applications of Incoloy 800H/HT
Alloys 800H/HT is used in a range of applications that involve exposure to corrosive environments and high temperatures such as heat treating equipment, chemical and petrochemical processing, nuclear power plants and the paper pulp industry.
Heat-treating equipment such as baskets, trays, and fixtures employ Incoloy 800H/HT. Petrochemical and chemical industries use the alloys for heat exchangers and other piping systems in nitric acid media especially where resistance to chloride stress-corrosion cracking is required. Power plants use them for super-heater and re-heater tubing.
The applications of Incoloy 800H/HT are:
- Hydrocarbon cracking
- Ethylene furnace quench boilers
- Super-heater and re-heaters in power plants
- Heat exchangers
- Pressure vessels
- Valves, fittings and other components exposed to corrosive attack from 1100-1800° F
- Heat-treating equipment
- Industrial furnaces
- Chemical and petrochemical processing.
This information has been sourced, reviewed and adapted from materials provided by Yaang Pipe Industry.
For more information on this source, please visit Yaang Pipe Industry .
