Inconel 825 Flanges
Inconel 825 Flanges (UNS N08825) Nickel Alloy Flanges
Inconel 825 Flanges, designated as UNS N08825, are engineered from a highly corrosion-resistant nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. This alloy provides outstanding resistance to a wide range of corrosive environments, including sulfuric acid, phosphoric acid, seawater, and chloride-rich conditions.
Due to its excellent resistance to stress-corrosion cracking, pitting, crevice corrosion, and oxidation, Inconel 825 is widely used in chemical processing, oil & gas, marine engineering, pollution control, and nuclear fuel reprocessing plants. It delivers reliable performance from cryogenic temperatures to 540°C, making it a trusted material for demanding industrial applications.
Key Features
Exceptional resistance to strong acids (sulfuric, phosphoric, nitric)
Outstanding resistance to stress-corrosion cracking in chlorides
Excellent performance in high-temperature and high-pressure systems
Superior resistance to pitting & crevice corrosion
High tensile and yield strength
Good weldability and formability
Stable mechanical properties up to 540°C
Titanium stabilization for improved resistance to intergranular corrosion
Reliable for both oxidizing and reducing environments
Specifications
| Specification | Details |
|---|---|
| Standard | ASTM B564, ASME SB564 |
| Material | Inconel 825 / Alloy 825 |
| UNS Number | N08825 |
| Werkstoff Nr. | 2.4858 |
| Flange Types | WN, SO, BL, SW, Threaded, Lap Joint, RTJ, Orifice, Long Weld Neck |
| Size Range | ½” to 48” |
| Pressure Rating | Class 150 to 2500 / PN6–PN400 |
| Manufacturing | Forged, Heat Treated, Machined |
| Face Type | RF, RTJ, FF |
| Design Standards | ASME B16.5, B16.47, B16.48, DIN, EN, BS |
Equivalent Grades
| Standard | Grade |
|---|---|
| UNS | N08825 |
| Werkstoff | 2.4858 |
| Trade Name | Inconel 825, Alloy 825 |
Available Sizes
Standard Size Range: ½” to 48”
Pressure Class: 150 – 2500
Custom Machining & Special Sizes: Available on request
Chemical Composition
| Element | Percentage (%) |
|---|---|
| Nickel (Ni) | 38.0 – 46.0 |
| 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 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 0.5 |
| Carbon (C) | ≤ 0.05 |
| Sulfur (S) | ≤ 0.03 |
| Aluminum (Al) | ≤ 0.2 |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | 690 MPa (min) |
| Yield Strength (0.2% offset) | 275 MPa (min) |
| Elongation | 30% (min) |
| Hardness | 85 HRB (typical) |
| Impact Strength | High toughness across temperature range |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.14 g/cm³ |
| Melting Point | 1370–1400°C |
| Thermal Conductivity | 11.2 W/m·K |
| Electrical Resistivity | 1.21 µΩ·m |
| Specific Heat | 0.44 kJ/kg·K |
| Modulus of Elasticity | 195 GPa |
Types of Inconel 825 (UNS N08825) Flanges
Weld Neck Flanges
Slip-On Flanges
Blind Flanges
Socket Weld Flanges
Threaded Flanges
Lap Joint Flanges
Ring Type Joint (RTJ) Flanges
Orifice Flanges
Reducing Flanges
Long Weld Neck Flanges
Corrosion Resistance
Inconel 825 (UNS N08825) offers outstanding corrosion resistance against:
Sulfuric, phosphoric, and nitric acids
Hydrochloric acid (moderate concentrations)
Alkalis and caustic solutions
Seawater and brine
Reducing and oxidizing chemicals
Stress-corrosion cracking in chloride environments
Pitting and crevice corrosion
The alloy’s titanium stabilization also ensures resistance to intergranular attack after welding.
Heat Resistance
Reliable performance up to 540°C
Strong resistance to oxidation and carburization
Suitable for heater tubes, heat exchangers, and chemical reactors
Maintains high strength and corrosion resistance at elevated temperatures
Heat Treatment
Inconel 825 is typically supplied in the annealed condition.
Standard Heat Treatment
Annealing Temperature: 1700–1800°F (925–980°C)
Cooling: Rapid air or water quenching
Heat treatment enhances ductility, corrosion resistance, and stabilization against sensitization.
Welding
Inconel 825 (UNS N08825) offers excellent weldability using:
Recommended Processes
GTAW (TIG)
GMAW (MIG)
SMAW
Submerged Arc Welding
Common Filler Metals
Alloy 825 Weld Wire
Inconel 625 Filler Metal
The alloy resists post-weld grain boundary sensitization due to titanium stabilization.
Fabrication
Good hot and cold workability
Hot working temperature: 1600–2150°F (870–1180°C)
Excellent formability and machinability
Carbide tools recommended for machining
Suitable for forging, bending, shaping, and pressing
Applications
Chemical processing equipment
Acid production plants
Oil & gas offshore platforms
Heat exchangers and condensers
Marine and seawater systems
Pollution control & waste treatment
Nuclear fuel reprocessing
Desalination plants
Petrochemical equipment
Pickling tank heaters and piping systems