Alloy 825 (UNS N08825)


Alloy 825 is an austenitic nickel-iron-chromium-molybdenum-copper alloy containing high levels of chromium, nickel, molybdenum and copper to provide high levels of corrosion resistance to both moderately oxidizing and moderately reducing environments. The alloy has a high level of nickel, which in combination with the level of molybdenum and copper, produces substantially improved corrosion resistance in reducing environments compared to the standard stainless steels.  The nickel content is sufficiently high to provide superb resistance to chloride stress corrosion cracking. The chromium and molybdenum content of the alloy provides a level of resistance to chloride ion pitting.  In addition, the alloy is stabilized against sensitization in the welded condition by the addition of a specified level of titanium. Because of this stabilization, the material is resistant to intergranular attack after exposure in the temperature range, which would sensitize unstabilized stainless steels.

Alloy 825 has a long history of use in many corrosive environments and has been incorporated in ASTM and ASME specifications for many years. As an austenitic, nickel-base alloy, the material is ductile over a wide range of temperatures from cryogenic to well in excess of 1000°F (538°C).

Chemical Composition

Chemical Composition (wt%) limits as specified in ASTM B425*

Carbon 0.05 Manganese 1.0
Chromium 19.5-23.5 Silicon 0.5
Nickel 38.0-46.0 Copper 1.5-3.0
Iron 22.0 min Aluminum 0.1-0.5
Molybdenum 2.5-3.5 Sulfur 0.03
Titanium 0.6-1.2    

*Maximum, unless range is indicated

Physical Properties

Physical properties for Alloy 825

Density, lb/in3 0.293
Modulus of Elasticity, psi 28.3 x 106
Coefficient of Thermal Expansion, 68-212˚F, /˚F 7.7 x 10-6
Thermal Conductivity, Btu/ft hr ˚F 6.4
Specific Heat, Btu/lb ˚F 0.12
Electrical Resistivity, Microhm-in 44.5

Mechanical Properties

Mechanical property requirements as specified for annealed product in ASTM B 425

Yield Strength, min. (ksi) 35
Tensile Strength, min. (ksi) 85
Elongation, min. (%) 30


Typical standards for Alloy 825