Hastelloy Intergranular Corrosion in Weld Metal
Corrosive attack at grain boundaries of welded nickel alloys caused by chromium and molybdenum depletion resulting from inadequate cooling rates during welding.
Hastelloy and similar nickel-based alloys can become susceptible at the grain boundaries after welding if they cool too slowly through the critical temperature range. Alloying elements such as chromium and molybdenum, which normally provide corrosion protection, migrate away. The result is fine cracks or pitting at the weld, especially if the component later comes into contact with aggressive media. To prevent this, keep the heat input low and let the weld cool quickly after welding. You can achieve this, for example, with copper backing or active cooling from the other side. It is important to keep an eye on the interpass temperature and not put too much heat into the part. If you manage the weld cleanly with controlled cooling, the structure remains stable and corrosion resistance is maintained.