Cost Effective Weld Overlay Alloys for Waste-to-Energy Systems

Abstract Alloy 625 (UNS N06625) has successfully been used as a weld overlay for many years in waste-to-energy systems to combat corrosion. UNS N06625 will likely remain the preferred alloy for the most aggressive regions of the boiler; however there are other regions in the system where leaner and less costly weld overlay materials are more than sufficient. Alloy 31 (UNS N08031), with 31%Ni-28%Cr-6.5%Mo, has been tested in both the laboratory and in the field with corrosion resistance approaching that of UNS N06625 in many cases and is significantly less expensive than UNS N06625. A comparison of the corrosion resistance of UNS N08031against other alloys is presented. In addition, field data is presented from various field tests and is shown to support laboratory corrosion based empirical model previously suggested by other researchers. This model is used to project the corrosion response of UNS N08031 in the field, which is further supported by 2 year field exposures in one boiler. Lastly an economic analysis is used help select the best material for various locations in the waste-to-energy boiler.