Inconel alloy 686 (UNSN06686 W.)nr.2.4606) is a single-phase austenitic Ni-Cr-Mo-W alloy with excellent corrosion resistance in a range of harsh environments. Its high nickel (Ni) and molybdenum (Mo) provide good resistance under reducing conditions, while high chromium (Cr) provides resistance to oxidizing media. Molybdenum (Mo) and tungsten (W) help resist localized corrosion, such as pitting. Iron (Fe) is tightly controlled to improve performance. Low carbon (c) helps to reduce grain boundary precipitation, thereby maintaining the corrosion resistance of the heat-affected zone of welded joints. As the alloy (Cr+Mo+W) content increases, the ability to resist full-scale corrosion, pitting and crevice corrosion increases, and Inconel Alloy 686 scores higher than competing materials.
Chemical composition. The chemical composition of Inconel 686 superalloy is as follows:
Nickel (Ni): 50-60%.
Chromium (CR): 19-23%.
Molybdenum (Mo): 15-17%.
Iron (Fe): 5-8%.
Cobalt (CO): 2-4%.
Copper (Cu): 05-2.5%
Titanium (Ti): 03-0.9%
Aluminium (Al): 02-0.8%
The alloy also contains trace amounts of elements such as carbon (C), phosphorus (P), sulfur (S) and boron (B). Among them, the addition of molybdenum can improve the strength and corrosion resistance of the alloy, the addition of copper can improve the corrosion resistance of the alloy, and the addition of cobalt can improve the high-temperature performance of the alloy.
Inconel 686 has the following features:
1.It has good resistance to corrosion of reduction, oxidation and nitriding media.
2.It has good resistance to stress corrosion cracking at room temperature and high temperature.
3.It has very good resistance to dry chlorine and gas corrosion.
4.It has good mechanical properties at sub-temperature, room temperature and high temperature.
5.It has very good creep rupture strength and is recommended for use above 700 °C.