High-Temperature Corrosion of Burner Tube Alloys Exposed to Flue Gas and Reducing Atmosphere Used for Annealing—A Laboratory Study

A demand for greater throughput and quality causes a ditto demand for higher temperatures in the annealing furnaces. The burners used for this application are already operating close to their upper temperature limit. This causes increased wear of the materials used in the burners and shortens their life-time considerably. The wear is caused by several factors such as creep and high temperature corrosion. The burners are in contact with two distinct types of atmospheres, the flue gas inside the burner and the annealing gas on the outside. The latter could be either H₂+N₂ mixtures, H₂, Ar or air. One way to increase the life time could be to use Al₂O₃ forming alloys instead of Cr₂O₃ formers. In this study the high temperature corrosion behaviour in flue gas as well as annealing gas of two such alloys has been investigated on lab scale.

The alloys involved were spun cast Centralloy^® 60 HT R (Al₂O₃) and G-NiCr28W (Cr₂O₃), they were exposed at 1100 and 1200°C for up to 500 h. Three atmospheres were used: a simulated flue gas  5.6%O₂/14.7%H₂O/8.1%CO₂/71.6%N₂, and two annealing atmospheres, 100%H₂ and 25%H₂/75%N₂ both with traces of O₂. The exposed samples were analysed by TG, SEM/EDX and GI-XRD.