Incoloy alloy 825 is a nickel iron, chromium alloy with combinations of molybdenum, copper and titanium, with excellent resistance to numerous aggressive corrosion environments. Incoloy 825 is extremely resistant to corrosion. It has a high nickel content, enough to resist chloride ion stress corrosion cracking, and a very stable austenite configuration. The levels of molybdenum and copper gives the alloy a high resistance to reducing agents and acids. Chromium enables resistance to oxidizing conditions, such as nitric acid solutions, nitrates and oxidizing salts. The alloy is titanium stabilized to prevent pitting and intergranular attack after fabrication, especially welding, which involves heating in the critical sensitization temperature range (650 °C – 760 °C).
This alloy possesses good ductility and may be formed by all orthodox methods. Because the alloy is stronger than regular steel it needs more powerful equipment in forming. Heavy-duty lubricants should be used during cold forming. It is important to clean the part of all traces of lubricant after forming as embrittlement of the alloy may occur at high temperatures if lubricant is left on.
Alloy 825 offers exceptional resistance to corrosion by sulfuric and phosphoric acids and is often the most cost effective alloy in sulfuric acid service. Incoloy 825 is approved for pressure vessel operating temperatures up to 525 °C, 538 °C. Brittle phases may develop in alloy 825 at temperatures above 540 °C, so it is not generally used at these temperatures, where creep-rupture properties would be considered in the design.
The commonly used welding methods work well with this alloy. Matching alloy filler metal should be used. If matching alloy is not available, then the nearest alloy richer in the essential chemistry (Ni, Co, Cr, Mo) should be used. All weld beads should be slightly convex. It is not necessary to use preheating