Investigation of Iron Aluminide Weld Overlays

Corrosion and subsequent waterwall wastage has been a significant problem for coal-burning power companies since low NOx burner conditions have been implemented in their furnaces. In order to reduce the amount of waterwall corrosion, coatings for the boiler tubes, such as weld overlay claddings, are currently being pursued. Iron-aluminum based coatings are presently being studied as possible coating candidates due to their excellent corrosion resistance in hightemperature oxygen and sulfur bearing environments. In addition, iron-aluminum based alloys are advantageous to other possible coating candidates because they are cheaper than stainless steel or Ni-based superalloys and do not demonstrate microsegregation of alloying elements unlike Ni-based superalloys. Unfortunately, iron-aluminum weld overlay claddings are susceptible to hydrogen cracking at aluminum contents greater than 10wt%Al. It has previously been shown that the corrosion resistance of iron-aluminum alloys is directly related to the aluminum content of the alloy. Therefore, chromium was added to iron-aluminum alloys to determine if they promoted the corrosion resistance in several corrosive environments.