Introduction Of Incoloy 800
Incoloy 800 alloy is a Ni-Fe-Cr alloy used to resist oxidation and carbonization. Its nickel content reaches 32%, which makes 800 alloy have good resistance to chlorine-induced stress corrosion cracking and precipitation of σ phase to make the alloy brittle. 800 alloy is also excellent in uniform corrosion resistance. In the solution treatment state, 800H and 800AT have outstanding creep and stress rupture properties. The 800 series alloys are basically the same, except that the carbon content in 800H is slightly higher (0.05-0.10%), and 1.00% Al+Ti is added to 800AT. 800 alloy can generally be used up to 593°C. 800H and 800AT are generally used at temperatures above 593°C, which require high requirements for creep and stress corrosion cracking.
The nickel content of the 800 series alloy is much higher than that of the 304 stainless steel family. In many media conditions, the 800 series alloy and 304 stainless steel are very similar. For example, in many industrial gases and chemical media such as nitric acid and organic acids, they have considerable performance. Neither the 800 series alloy nor the 304 stainless steel can be used in a sulfuric acid environment, unless it is a low temperature and low concentration situation. Like austenitic stainless steel, if the 800 series alloy is heated for too long in the range of 538℃-760℃, chromium carbides will precipitate at the grain boundaries of the alloy, which will cause the alloy to appear sensitized and make the alloy behave like pickling. Intergranular corrosion occurs in the environment of high temperature and 65% nitric acid environment.
Although the 800 series alloy has no immunity to chloride ion stress corrosion cracking, its corrosion resistance is still very good. It has good corrosion resistance in petroleum, chemical, food, pulp and paper industries. Obviously, the 800 series alloy can be used in a moderately corrosive environment that causes stress corrosion fracture of ordinary austenitic stainless steel. However, the 800 series alloy has no immunity to the stress corrosion cracking of MgCl2 solution.
The most typical application of 800 alloy is high temperature applications, such as incinerator components, petrochemical reformers, hydrocracking pipe fittings, superheated steam treatment equipment in conventional power plants and nuclear power plants. The high content of chromium and nickel makes the 800 series alloys have good resistance to oxidation and carbonization.
In summary, the 800 series have the following characteristics:
(1) According to the ASME standard, it has high design strength when applied at 899℃;
(2) The tube can be used at a temperature below 982°C;
(3) There is still oxidation resistance at 1038℃;
(4) Resistance to chloride ion corrosion.
