Alloy 625 Grade 1

625 Alloy Grade 1 / UNS N06625 / W.NR. 2.4856
Description
625 Alloy is a nickel-chromium-molybdenum alloy that combines high strength, toughness, and excellent corrosion resistance. The strength of 625 Alloy is derived from the strengthening of its nickel-chromium matrix by molybdenum and niobium. Although the alloy was developed primarily for high temperature strength, its highly alloyed composition also provides excellent corrosion resistance.

Industries & Applications
625 Alloy is used in a wide variety of industries including automotive, marine, aerospace, oil & gas, chemical, and nuclear. Typical end uses include heat exchangers, bellows, expansion joints, exhaust systems, fasteners, quick connects, and many other applications requiring high strength and resistance to corrosive environments.

Corrosion Resistance
625 Alloy has good resistance to oxidation and scaling at elevated temperatures. At temperatures up to 1800°F (approximately 844°C), oxidation resistance becomes an important factor in its use. It outperforms many other high temperature alloys under cyclic heating and cooling conditions. The combination of alloying elements in 625 alloy enables it to withstand a wide range of severe corrosive environments. In mild environments, such as fresh and seawater, neutral pH environments, and alkaline media, little corrosion occurs. The alloy's chromium content gives it excellent oxidation resistance. The high molybdenum content makes 625 alloy extremely resistant to pitting and crevice corrosion.

Fabrication and Heat Treatment
625 alloy can be formed using a variety of cold and hot working processes. 625 alloy does not deform easily at hot working temperatures, so higher loads are required to form the material. Hot forming should be performed in the temperature range of 1700°F (about 744°C) to 2150°F (about 1054°C). During cold working, the material work-hardens faster than conventional austenitic stainless steels. Alloy 625 is available in three heat treatments: 1) solution annealed (2000/2200°F) and air quenched or faster; 2) annealed (1600/1900°F) and air quenched or faster; 3) stress relieved (1100/1500°F) and air quenched. Solution annealed (Grade 2) material is typically used above 1500°F where creep resistance is critical. Soft annealed (Grade 1) material is typically used at lower temperatures and has the best combination of tensile and fracture properties.