UNS N08825 nickel-iron-chromium-molybdenum-copper alloy
UNS N08825 is an austenitic nickel-iron-chromium-molybdenum-copper alloy containing high levels of chromium to provide a high level of corrosion resistance to moderate oxidation and moderate reduction environments. The alloy has high levels of nickel, which, combined with levels of molybdenum and copper, produce significantly improved corrosion resistance in a reducing environment compared to standard stainless steel. The nickel content is high enough to provide excellent resistance to chloride stress corrosion cracking.
The chromium and molybdenum content of the alloy provides some degree of resistance to chloride pitting, but not to the level of N06625 alloy. In addition, by adding a specific level of titanium, the alloy is stable and non-sensitizing under welding conditions. Because of this stability, the material is able to resist intergranular erosion after exposure to a temperature range that would sensitize unstable stainless steels.
Corrosion resistance
UNS N08825 alloy is an austenitic alloy containing high levels of chromium, nickel, molybdenum, and copper. The alloy has a high level of nickel and provides excellent resistance to chloride stress corrosion cracking. However, in the magnesium chloride test, which boils extremely violently, alloy 825 will crack in a certain percentage of the test sample during a long period of time.
The alloy is resistant to chloride stress corrosion cracking. In real-world use environments, Alloy 825 is a good material choice, offering extreme resistance to chloride stress corrosion cracking comparable to E-Brite alloys. General corrosion resistance to moderately oxidizing and moderately reducing environments.
Formability
UNS N08825 alloy is easy to cold form and has the typical forming behavior of high-nickel materials. This alloy exhibits good ductility and is suitable for deep drawing, spinning, and bending. This material is slightly stronger than carbon steel, but the work hardens not as quickly as the familiar stainless steel.
Solderability
UNS N08825 alloy is easy to weld by inert gas, metal arc or resistance welding. Generally, no preheating or post-weld heat treatment is required. Argon or helium is commonly used for shielding. A high-alloy filler material that matches the corrosion resistance of the base metal should be selected. Although the material is designed to resist the precipitation of chromium carbide through the low carbon content of the material and the titanium content, it is best practice to avoid the low carbon content of the material to 816°C. Surface cleanliness prior to welding is key to successful manufacturing and is necessary to maintain the high corrosion resistance of the material design.
Heat treatment
UNS N08825 alloy is an austenitic material that cannot be hardened by heat treatment. The annealing cycle used for Al 825 alloy typically consists of heating to a temperature range of 1700 to 1900 °F (927 to 1038 °C), holding until the material reaches a uniform temperature, followed by air cooling or water quenching.
The aim is to soften the material after the forming operation while maintaining a relatively fine grain size. To improve resistance to intergranular corrosion (sensitization), stabilization should be performed at temperatures of 1600 to 1750°F (870-955°C) for one hour or more. Heat treatment in high-temperature environments containing high levels of sulfur or exposure to high-temperature environments is harmful to Alloy 825 and should be avoided.
uns n08825Chemical composition.
c 0.02
mn0 .50
p 0.025
s 0.002
si 0.25
cr 21.0
ni 40.0
mo2.8cu2.3
ti 1.0
al 0.15
FE margin. 