About HY INCOLOY 825
Material grades and equivalents：
German standard: 2.4858
Japanese standard: NCF825
American Standard: UNS N08825
National standard: 0Cr21Ni42Mo3Cu2Ti
Incoloy 825 is a nickel-iron-chromium austenitic alloy with added molybdenum, copper and titanium. It has special corrosion resistance in oxidizing and reducing environment. Incoloy alloy has good general corrosion resistance and local corrosion resistance and good process performance. Therefore, it has been widely used in the chemical, energy, petrochemical, and hydrometallurgical industries.
Chemical composition and organizational characteristics
The balance between the nickel equivalent and the chromium equivalent in the alloy composition determines the pure austenite structure of the alloy under solid solution conditions. However, during medium temperature aging, carbides and intermetallic compounds will be precipitated on the austenite matrix and intergranular. These precipitation phases will harm the mechanical properties and corrosion resistance of the alloy.
Table 1: Incoloy 825 grade and chemical composition comparison table：
Incoloy 825 has good corrosion resistance to various processing environments, including sulfuric acid, sulfurous acid, phosphoric acid, nitric acid, hydrofluoric acid, organic acids and alkalis such as sodium, potassium hydroxide, and acid chlorides.
Compared with general austenitic stainless steel, the nickel in Incoloy825 makes it resistant to chloride stress corrosion, while molybdenum and copper make it highly resistant to corrosion in a reducing environment. Chromium and molybdenum components can resist chloride pitting corrosion and corrosion in various oxidizing environments. The addition of titanium makes the material more stable during welding and is not easy to sensitize. This non-sensitization property allows the material to resist intergranular corrosion even when exposed to the sensitization temperature range.
It is not sensitive to intergranular corrosion under the condition of solution treatment at 1150～1204℃. When the medium temperature sensitization treatment for 1 hour, such as 760℃, chromium-rich M23C6 will precipitate on the grain boundaries, which will lead to the boiling of 65% HNO3 The intergranular corrosion. However, a stabilization treatment at 940°C for 1 hour before sensitization can prevent intergranular corrosion caused by sensitization.
Table 2: Room temperature mechanical properties of Incoloy825
|Material heat treatment state||Mechanical properties|
|Solution Annealed Pipe||608～647||264～323||44～53||—|