What Is Incoloy 825

Properties of incoloy 825

lncoloy 825 is an austenitic nickel-iron-chromium-molybdenum-copper alloy containing high levels of chromium, nickel, copper and molybdenum to provide high levels of corrosion resistance to both moderately oxidizing and moderately reducing environments. This balance of alloying elements grants this alloy exceptional resistance to both chloride stress corrosion cracking, as well as crevice corrosion and general corrosion. It is the high level of nickel in combination with the amount of molybdenum and copper in this nickel alloy produces substantially improved corrosion resistance in a corrosive environment such as reducing environments compared to stainless steel. The addition of titanium in this alloy also helps to stabilize the alloy against intergranular corrosion. Chloride stress corrosion cracking is a type of localised intergranular corrosion on materials that are put under tensile strength, in high temperatures and in an environment that includes oxygen and chloride ions such as seawater.

This nickel steel alloy’s chemical composition is designed to provide exceptional resistance to many corrosive environments. It is similar to alloy 800 but has improved resistance to aqueous corrosion. It has excellent resistance to both reducing and oxidizing acids, to stress-corrosion cracking, and to localized attack such as pitting and crevice corrosion. Alloy 825 is especially resistant to sulfuric and phosphoric acids. This nickel steel alloy is used for chemical processing, pollution-control equipment, oil and gas well piping, nuclear fuel reprocessing, acid production, and pickling equipment.

The nickel content of Alloy 825 makes it resistant to chloride stresscorrosion cracking, and combined with molybdenum and copper, provides substantially improved corrosion resistance in reducing environments when compared to conventional austenitic stainless steels. The chromium and molybdenum content of Alloy 825 provides resistance to chloride pitting, as well as resistance to a variety of oxidizing atmospheres. The addition of titanium stabilizes the alloy against sensitization in the as-welded condition. This stabilization makes Alloy 825 resistant to intergranular attack after exposure in the temperature range which would typically sensitize un-stabilized stainless steels. Alloy 825 is resistant to corrosion in a wide variety of process environments including sulfuric, sulfurous, phosphoric, nitric, hydrofluoric and organic acids and alkalis such as sodium or potassium hydroxide, and acidic chloride solutions. The fabrication of Alloy 825 is typical of nickel-base alloys, with material readily formable and weldable by a variety of techniques.

Applications for incoloy 825

Phosphoric acid is predominantly used in the production of phosphate fertilisers. Therefore, any equipment used in process could be a candidate application, including piping, tanks, mixers, pumps and valves. Also heat exchangers, evaporators, washers and immersion pipes could utilise Alloy 825. Ferralium 255 and 904L are commonly specified for such applications, at a lower price and higher strength than Alloy 825, somewhat limiting applications. Other uses of phosphoric acid are in the food and beverage industry and also domestic products, meaning that it can find application in general engineering equipment as an alternative to Alloy 316L.

Sulphuric acid is also consumed in the production of fertilisers. However, it is also widely used in paper making as part of the bleaching process and to control pH during various process stages. Alternative grades to Alloy 825 used in pulp processing and paper making include duplex stainless steels (Sanmac 2205, 1.4462, UNS S32205) and a number of lean duplex stainless steel grades, although mostly as piping. Sulphuric acid is also used as a pickling agent for metals. Components such as heating coils, vessels, boilers, baskets and chains can make use of the good resistance to sulphuric acid of Alloy 825.

Alloy 825 is also strongly resistant to nitric acid, which is a strongly oxidising acid. It is again used in the production of fertilisers, but also in the manufacture of chemicals, and also the reprocessing of spent nuclear fuel. For this reason it has been used to fabricate a wide range of equipment associated with the handling of radioactive waste streams and nuclear fuel reprocessing. For instance, it has been used in nuclear fuel element dissolvers where a variety of corrosive media, e. g. sulphuric and nitric acids and sodium hydroxide, are handled in the same equipment.

As seawater is widely used as a coolant in many industries. Alloy 825 will find use in applications where there may also be additional contamination of the seawater that increases the corrosive nature, such as marine exhaust systems. Super duplex stainless steels would provide a more cost-effective solution for land-based scrubbers i.e. power stations that are operated continuously. However, as marine scrubbers see intermittent service, the temperature seen by any metal components can greatly exceed the permissible maximum for these alloys when the scrubber is not in operation.

Incoloy 825 provides exceptional corrosion resistance along with good weldability making it ideal for many applications where strength combined with durability are crucial factors for success – whether you’re looking into using this material for chemical processing plants or medical implants you can rest assured knowing that this alloy meets all standards set by ASTM International while offering excellent value compared to its more expensive counterparts like Titanium Alloys, etc.