Do You Know the Incoloy 825?

┃ Overview

UNS N08825 ( Alloy 825, W.Nr. 2.4858, Incoloy® 825) is an alloy composed of nickel, iron, and chromium, with additional elements such as molybdenum, copper, and titanium. This alloy exhibits exceptional resistance to various corrosive environments. Its high nickel content enables it to effectively withstand chloride-ion stress-corrosion cracking. The combination of nickel, molybdenum, and copper provides remarkable resistance to reducing environments, including those containing sulfuric and phosphoric acids. Moreover, the presence of molybdenum enhances its ability to resist pitting and crevice corrosion. Furthermore, the inclusion of titanium, along with suitable heat treatment, helps stabilize the alloy against intergranular corrosion sensitization.

┃ Application

Chemical Processing: Sulfuric acid plants, pickling operations, and production of phosphoric acid

Oil and Gas: Pipes, valves, pumps, and heat exchangers where corrosion resistance and high strength are required

Marine Applications: Offshore platforms, seawater cooling systems, and equipment exposed to saltwater environments

Pollution Control: Flue gas desulfurization systems, scrubbers, and exhaust systems

Nuclear Power Industry: Reactor components, heat exchangers, and piping systems

Food Processing:  Food processing equipment, including reactors, agitators, and vessels

┃ Chemical Composition (%)

┃ Mechanical Property

┃Corrosion Resistance

Incoloy 825 stands out for its exceptional corrosion resistance, making it highly suitable for applications involving sulfuric acid, phosphoric acid, sour flue gases, sour gases and oil wells, as well as seawater. This alloy exhibits resistance to general corrosion, pitting, crevice corrosion, intergranular corrosion, and stress-corrosion cracking in both reducing and oxidizing environments.

┃Heat Treatment

During the manufacturing process, Incoloy 825 products undergo heat treatment at the mill to achieve the desired combination of stabilization, corrosion resistance, mechanical properties, and formability. To preserve these properties during fabrication, it is recommended to carry out subsequent annealing processes within the temperature range of 1700 to 1800°F (930 to 980°C), followed by rapid air cooling or water quenching.

┃ Heating and Pickling

In order to remove scale, oxides, and other impurities from the surface of Incoloy 825, heating and pickling processes can be employed. These processes are typically conducted during fabrication or maintenance to enhance the material's cleanliness and improve its corrosion resistance. It is crucial to carry out the heating and pickling process in a controlled and well-ventilated environment, adhering to proper safety procedures. The specific parameters and procedures may vary depending on the thickness of the scale, available equipment, and recommendations provided by the pickling solution manufacturer. It is advisable to consult the manufacturer's guidelines or seek expert advice to ensure the appropriate heating and pickling process for Incoloy 825 in your specific application.

┃ Hot and Cold Forming

The hot-working temperature range for Incoloy 825 is typically 1600 to 2150°F (870 to 1180°C). To achieve optimal corrosion resistance, it is recommended to perform final hot working within the range of 1600 to 1800°F (870 to 980°C). After hot working, the cooling process should be air cooling or faster. It's important to note that thick sections may become susceptible to intergranular corrosion during cooling from hot working temperatures. In such cases, stabilization annealing can be employed to restore corrosion resistance.

When it comes to cold-forming, the properties and practices for alloy 825 are similar to those of Inconel 600. Although the rate of work hardening is slightly lower compared to common grades of austenitic stainless steels, it is still relatively high.

┃ Machining

Incoloy 825 can be easily machined using standard machining operations. The alloy is typically in its optimum annealed temper, which facilitates machining processes.

┃Welding

Incoloy 825 has exhibits good weldability and can be welded using various conventional processes. For most applications, the preferred choices are INCONEL® Welding Electrode 112 for shielded metal-arc welding and INCONEL Filler Metal 625 for gas-shielded processes. These options provide satisfactory results. However, for applications that demand the highest level of corrosion resistance, INCO-WELD® Welding Electrode 686CPT® and INCO-WELD Filler Metal 686CPT are recommended. These alternatives offer enhanced corrosion resistance properties.

┃ Product Forms

Ø Bar & Rod

Ø Plate & Sheet

Ø Coil & Strip

Ø Pipe & Tube

Ø Fitting: Flange, Tee, Elbow, Reducer etc.

Ø Forging: Ring, Shaft, Circle, Block etc.

┃ Note

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