# Alloy 825 UNS N08825: Properties and Applications
## Introduction to Alloy 825
Alloy 825, also known as UNS N08825, is a nickel-iron-chromium alloy with additions of molybdenum and copper. This material is designed to resist corrosion in various environments, making it a popular choice for industrial applications. Its excellent mechanical properties and resistance to stress corrosion cracking make it suitable for demanding conditions.
## Chemical Composition
The chemical composition of Alloy 825 plays a crucial role in its performance. Below is a breakdown of its key elements:
– Nickel (Ni): 38-46%
– Chromium (Cr): 19.5-23.5%
– Iron (Fe): Balance
– Molybdenum (Mo): 2.5-3.5%
– Copper (Cu): 1.5-3.0%
– Titanium (Ti): 0.6-1.2%
– Carbon (C): ≤0.05%
## Mechanical Properties
Alloy 825 exhibits impressive mechanical properties that contribute to its widespread use:
– Tensile Strength: 586 MPa (85 ksi) min
– Yield Strength: 241 MPa (35 ksi) min
– Elongation: 30% min
– Hardness: ≤200 HB
## Corrosion Resistance
One of the most notable features of Alloy 825 is its exceptional corrosion resistance:
– Excellent resistance to reducing and oxidizing acids
– Good resistance to stress corrosion cracking
– Performs well in sulfuric and phosphoric acid environments
– Resistant to pitting and crevice corrosion in chloride-containing solutions
## Heat Treatment
Alloy 825 can be heat treated to optimize its properties:
– Solution annealing is typically performed at 927-1038°C (1700-1900°F)
– Rapid cooling is required after annealing to prevent carbide precipitation
– Stress relieving can be done at 538-649°C (1000-1200°F)
## Applications
Keyword: Alloy 825 UNS N08825
Due to its unique combination of properties, Alloy 825 finds applications in various industries:
### Chemical Processing
– Acid production equipment
– Pickling tanks and heating coils
– Reactor vessels
### Oil and Gas Industry
– Downhole components
– Wellhead equipment
– Seawater handling systems
### Power Generation
– Flue gas desulfurization systems
– Heat exchangers
– Nuclear fuel reprocessing
### Marine Applications
– Seawater piping systems
– Propeller shafts
– Pump components
## Fabrication and Welding
Alloy 825 can be readily fabricated using standard techniques:
– Hot working should be performed at 1038-1177°C (1900-2150°F)
– Cold working requires intermediate annealing
– Welding can be done using matching filler metals (ERNiCrMo-3)
## Comparison with Similar Alloys
Alloy 825 is often compared to other nickel-based alloys:
– More resistant to sulfuric acid than Alloy 600
– Better chloride resistance than 316 stainless steel
– Superior to Alloy 800 in reducing acid environments
## Conclusion
Alloy 825 UNS N08825 offers an excellent combination of corrosion resistance, mechanical properties, and fabricability. Its versatility makes it suitable for numerous demanding applications across various industries. When selecting materials for corrosive environments, Alloy 825 should be considered as a reliable option that can provide long-term performance and durability.