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Description
Incoloy 800
Material
UNS N08800, Alloy 800, W.Nr. 1.4876, Incoloy® 800
Note that the designation “ Incoloy®” is registered trademarks of the Special Metals Corporation group of companies.
Overview
UNS N08800 is a nickel-based alloy designed for corrosion and high temperature environments. Due to the content of nickel, the alloy resists stress corrosion cracking, and maintains a ductile, austenitic structure. The chromium in the alloy imparts both aqueous and heat resistance. Iron provides resistance to internal oxidation. In addition, the alloy is readily formed, welded, and machined. These properties make incoloy 800 widely used material for construction of equipment requiring corrosion resistance, heat resistance, strength, and stability for service up to 1500°F (816°C).
Application
- In High Temperatures Applications: Heat-treating equipment such as baskets, trays, and fixtures
- In Chemical Processing: Heat exchangers and other piping systems in nitric acid media
- In Petroleum: Heat exchangers that air cool the process stream
- In Domestic Appliances: Sheathing of electric heating elements
- In Paper Pulp Production: Digester-liquor heaters
- In Nuclear Power Plants: Steam-generator tubing
Chemical Composition (%)
| Material | Ni | Cr | Fe | C | Mn | S | Al | Ti |
|---|---|---|---|---|---|---|---|---|
| N08800 | 30.0-35.0 | 19.0-23.0 | 39.5 min | 0.10 max | 1.50 max | 0.015 max | 0.15-0.60 | 0.15-0.60 |
Mechanical Property
| Material | Tensile strength | Yield strength 0,2 | Elongation | Hardness HB30 |
|---|---|---|---|---|
| N08800 | 500 N/mm² | 210 N/mm² | 35% | 135-179HB |
Corrosion Resistance
Incoloy 800, 800H and 800HT have the same nickel, chromium, and iron contents and generally display similar corrosion resistance. Same as many austenitic stainless steels, Incoloy 800 can be sensitized, or made susceptible to intergranular attack in some aggressive media, by exposure to the temperature range of 1000 to 1400°F (540–760°C). When Incoloy 800 is exposed to heat from welding or other operations, care should be taken to avoid sensitization if the material is to be pickled or subjected to other aggressive environments. Sensitization is not a problem in most high-temperature applications.
Heat Treatment
Incoloy 800 is a nickel-iron-chromium alloy known for its excellent resistance to oxidation, carburization, and high-temperature corrosion. Heat treatment can be used to enhance certain properties of Incoloy 800, such as grain size control and stress relief. The common heat treatment processes for Incoloy 800 is annealing, solution treatment and stress relieving. It's important to note that the specific heat treatment parameters may vary depending on the form and condition of the Incoloy 800 material, as well as the desired properties for a particular application.
Heating and Pickling
Before heating, Incoloy 800 to be heated must be cleaned of oil, paint, grease, shop soil and other foreign substances. When heating, all operations must be performed in a low-sulfur atmosphere. If heating is performed in an open air environment, It is necessary to use low-sulfur fuel and maintain in a reducing condition in the furnace atmosphere, to prevent excessive oxidation.
Because of the readiness with which chromium is oxidized into a refractory oxide by air, carbon dioxide or water vapor, Incoloy 800 cannot be bright annealed in the usual industrial annealing furnace, the alloy is normally annealed in box or muffle furnaces using prepared reducing atmospheres. Low-sulfur natural gas burned with a deficiency of air, It produces a thin, adherent, green-black film of oxide on the material, these oxide films and scales can be removed by pickling. Please note, because of Incoloy 800 inherent resistance to chemical attack, specialized pickling procedures are needed.
Hot and Cold Forming
The recommended temperature range of hot forming is 1600° to 2250°F (870° to 1230°C). Heavy forging should be done at temperatures from 1850°F to 2200°F (1010°C to 1200°C). Forming at temperatures between 1200 and 1600°F (650-870°C) can result in cracking of the workpiece. The rate of cooling following hot forming is not critical with respect to thermal cracking. However, Incoloy is subject to carbide precipitation in the 1000-1400°F (540- 760°C) temperature range and should be cooled rapidly through that range to avoid sensitization.
The cold forming of Incoloy 800 is done by procedures similar to those used for Inconel 600 and stainless steel. The work-hardening rate for they alloy 800 is essentially the same as the rate for Inconel 600, higher than the rate for mild steel but lower than that for 304 stainless steel.
Machining
Incoloy 800 is readily machined by standard methods. Turning operations can be performed with high metal removal rates, good tool life, and good surface finish using coated carbide tools. Good results have also been obtained with high-speed-steel tools, which are better for interrupted cutting.
Welding
Inconel 800 has good weldability by all welding processes. For shielded metal-arc welding of alloy 800, the recommended welding product is INCO-WELD A Electrode. For gas-tungsten-arc, gas-metal arc, and submerged-arc welding, INCONEL Filler Metal 82 is recommended. INCOFLUX 4 Submerged Arc Flux is used with the submerged-arc process.
Product Forms
- Bar & Rod
- Plate & Sheet
- Coil & Strip
- Pipe & Tube
- Fitting: Flange, Tee, Elbow, Reducer etc.
- Forging: Ring, Shaft, Circle, Block etc.
Note
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