A High Chromium Alloy for Weld Overlay of Superheaters in Coal Fired Power Plants

摘要

UNS R20033 is produced as a welding consumable and is covered under AWS A.9 under the designation of ER33-31. This material is now being widely used as weld overlay material in the fossil boiler industry. The high chromium content of ER33-31 has been shown to provide excellent corrosion protection in both waterwall and superheater/reheater tube applications. However, the main interest has been for use in convection pass tubes (i.e. superheater and reheater tubes). ER33-31 is applied to pressure tubing using a spiral clad weld overlay and is able to provide excellent resistance coal ash corrosion. Laboratory and field tests have shown ER33-31 to have among the best corrosion resistance of all materials studied. The application of ER33-31 is also easier than other more highly alloyed materials (such as FM-72) and is less expensive. A review of the favorable experiences of ER33-31 and the conditions under which ER33-31 should be considered are reviewed in this paper.