Super Austenitic Alloy 825, designated as UNS N08825, is a high-performance material characterized by its outstanding resistance to various corrosive environments. This alloy is particularly beneficial in applications within the chemical processing, oil and gas, and power generation industries, where both strength and corrosion resistance are paramount.
Physical Properties
In the annealed condition and with a temperature range from -20°F to +100°F, Alloy 825 exhibits notable physical properties. The tensile strength of this alloy reaches up to 85,000 psi (586 MPa), while the yield strength is approximately 35,000 psi (240 MPa). This strong combination provides the material with robust performance capabilities, essential for demanding applications. Additionally, the elongation in 2 inches is a minimum of 30%, demonstrating its excellent ductility, which is a crucial factor in fabricating and forming processes.
Composition
The composition of Super Austenitic Alloy 825 plays a vital role in its performance characteristics. The alloy consists primarily of Nickel (Ni) at 38.0–46.0%, Chromium (Cr) at 19.5–23.5%, and Iron (Fe) with a minimum of 22.0%. The incorporation of Molybdenum (Mo) at 2.5–3.5% enhances corrosion resistance, especially against chloride-induced stress corrosion cracking. Additionally, this alloy contains small percentages of other elements such as Titanium (Ti), Copper (Cu), and Manganese (Mn), each contributing specific properties essential for high-performance applications.
Mechanical Properties
The mechanical properties of Alloy 825 are further defined by specific requirements:
- Minimum Elongation: 30% in 2 inches ensures ductility.
- Grain Size Requirement: Not specified but generally, fine grain sizes improve strength and toughness.
- Maximum Hardness: Although not provided in the data, it is crucial for maintaining formability.
- Modulus of Elasticity: Approximately 28.0 x 10^6 psi, indicating good elasticity and resilience under stress.
Thermal Properties
In addition to its mechanical properties, Alloy 825 demonstrates favorable thermal properties, with a mean coefficient of thermal expansion of 7.7 x 10^-6 IN./IN./°F and thermal conductivity of 77 BTU-in/ft²-h-°F. These characteristics facilitate its application in environments experiencing thermal fluctuations.
Industry Standards
Super Austenitic Alloy 825 conforms to various industry specifications, which often include standards from organizations such as ASTM, ASME, and others. Typically, these specifications ensure that alloys are manufactured and tested according to high-pressure and temperature requirements, especially in critical applications such as:
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ASTM B704/B705: Outlining the requirements for seamless and welded nickel alloy pipes and tubes made from corrosion-resistant materials.
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ASME Boiler and Pressure Vessel Code: Ensures that materials used in pressure vessels meet rigorous safety and quality standards.
Applications
Given its unique chemical and physical properties, Alloy 825 is widely used in several challenging environments, including:
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Chemical Processing: Due to its superior resistance to pitting, crevice corrosion, and stress corrosion cracking, this alloy is ideal for components such as heat exchangers and reactors.
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Oil and Gas Industry: Utilized in pipelines, downhole tubing, and other applications where exposure to harsh environments is common.
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Power Generation: Employed in flue gas desulfurization units and other applications requiring high corrosion resistance at elevated temperatures.
Conclusion
Super Austenitic Alloy 825 stands out as a versatile and robust material, offering excellent mechanical and thermal properties that meet the demanding standards of various industries. Its unique composition provides exceptional resistance to corrosion, making it an ideal choice for applications in aggressive environments. Whether for use in chemical processing, oil and gas, or power generation, Alloy 825 is engineered to deliver enhanced performance, reliability, and safety.
For more information regarding specifications, properties, and applications, professionals are encouraged to refer to relevant industry standards and guidelines to ensure compliance and optimal performance in their specific applications.
