Incoloy 825 | Alloy 825 | UNS N08825 | Nickel Alloy

Inconel 825 (also known by its alloy number N08825) is a highly corrosion-resistant nickel-iron-chromium alloy with significant strength at elevated temperatures. It is designed for use in harsh environments where resistance to both high temperature and corrosion is essential. Here is a detailed introduction to the Inconel 825 alloy (N08825):

Chemical Composition

Inconel 825 is primarily composed of:

This alloy also contains trace amounts of other elements such as phosphorus (P) and boron (B).

Properties

Corrosion Resistance:

• Excellent Resistance to Corrosion: Inconel 825 is particularly resistant to a wide range of aggressive media, including sulfuric acid, phosphoric acid, and organic acids. It has strong resistance to stress corrosion cracking, pitting, and crevice corrosion, especially in acidic environments.
• Resistance to Chloride Pitting: The alloy’s molybdenum content provides excellent resistance to chloride-induced pitting, making it suitable for marine environments.
• Good Resistance to Reducing and Oxidizing Environments: Inconel 825 can resist both oxidizing acids, such as nitric acid, and reducing acids like sulfuric acid, providing versatility in chemical industries.

High-Temperature Strength:

• Inconel 825 has good mechanical strength at elevated temperatures, typically maintaining its strength at temperatures up to 1000°F (538°C). This makes it suitable for high-temperature industrial applications, including equipment exposed to hot gases, oils, and other corrosive fluids.

Excellent Weldability:

• It is known for its excellent weldability, which is beneficial in manufacturing processes that require joining, such as in the fabrication of pressure vessels, piping, and heat exchangers. The alloy can be welded using standard techniques like TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) welding.

Good Fabricability:

• Inconel 825 can be easily fabricated and formed into complex shapes due to its excellent cold working and hot working properties.

Applications

Inconel 825 is widely used in industries where resistance to corrosive environments and high temperatures is critical. Key applications include:

Chemical and Petrochemical Industry:

• Heat Exchangers: Inconel 825 is used in heat exchangers that are exposed to acidic and corrosive environments, such as those in sulfuric acid, phosphoric acid, and other aggressive chemicals.
• Piping Systems: It is commonly used for piping in aggressive chemical environments, such as in acid production, fertilizer manufacturing, and chemical processing plants.
• Pressure Vessels: It is used in the fabrication of pressure vessels and tanks for handling aggressive chemicals and high-pressure conditions.

Nuclear Industry:

• Reactor Components: Due to its resistance to radiation-induced corrosion, Inconel 825 is used in nuclear reactors for components like heat exchangers and other parts that need to withstand high temperatures and corrosive environments.

Marine and Offshore:

• Offshore Drilling Equipment: Inconel 825’s resistance to seawater corrosion makes it ideal for offshore drilling platforms, desalination plants, and other marine applications.
• Marine Exhaust Systems: It is used in marine exhaust systems where high temperatures and corrosive seawater may be present.

Flue Gas Desulfurization Systems:

• The alloy is used in components exposed to sulfur gases in power plants, where it helps in reducing sulfur emissions.

Food Processing and Pharmaceutical Industry:

• Corrosion-resistant Tanks and Vessels: Inconel 825 is used in the construction of tanks, vessels, and reactors in the food and pharmaceutical industries where resistance to acids is required.

Aerospace:

• Aircraft Engine Components: Inconel 825 is used in aerospace applications that require materials to perform in both high-temperature environments and corrosive conditions.

Product Forms

Inconel 825 is available in various forms to meet different manufacturing requirements, including:

• Sheet and Plate: Used in the fabrication of large structural components, pressure vessels, and heat exchangers.
• Bar and Rod: Commonly used for producing components that require high strength, such as shafts, bolts, and fasteners.
• Pipe and Tube: For use in chemical and petrochemical industries where resistance to corrosion and high temperature is necessary.
• Welding Wire and Filler Material: Used for joining Inconel 825 parts using welding techniques.
• Forgings: Used for high-strength components that require superior resistance to thermal and corrosive stress.

Standards

Inconel 825 conforms to several standards depending on its application:

• ASTM B425: Standard specification for Inconel 825 alloy in various forms, including plates, sheets, bars, and forgings.
• ASTM B366: Standard specification for Inconel 825 pipe fittings.
• ASME SB-425: Used for pressure vessels, heat exchangers, and related equipment in high-temperature applications.
• NACE MR0175: Inconel 825 meets the requirements for sour gas service in oil and gas applications.

Inconel 825 (N08825) is a versatile, highly corrosion-resistant, and heat-resistant nickel-based alloy that is used in a variety of harsh environments. It excels in applications where materials are exposed to both high temperatures and aggressive chemicals, such as in the chemical, petrochemical, aerospace, and marine industries. Its excellent weldability, high strength, and ability to resist corrosion make it an essential material in industries dealing with acids, chlorides, and high-pressure environments.