Alloy 625 has excellent heat and corrosion resistance and is commonly used in steam generation with a service temperature up to 450°C. It is frequently applied in the cladding of membrane walls, evaporators and preheaters.
Alloy 686 has a very high pitting resistance equivalent number PREN and, thanks to a higher nickel and molybdenum content, it has an higher resistance to corrosion in reducing environment, making it suitable for the cladding of heater pipes with temperatures above 450°C.
For the corrosion and oxidation resistance of the weld overlay, not only the chemistry of the welding consumable used is decisive. The welding process and the welding parameters have a direct influence on the overlay chemistry. To optimize this resistance, a low Fe content is aimed for, which is why low heat input techniques are used. By optimizing the GMAW pulse process, Böhler Welding has developed the clad pulse process to reduce the dilution with the base material during welding and thus lower the Fe content of the overlay.