11191 High Temperature Corrosion of Burner Tube Alloys Exposed to Flue Gas and Reducing Atmosphere Used for Annealing-A Laboratory Study

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Product Number: 51300-11191-SG

ISBN: 11191 2011 CP

Author: Henrik Asteman, Walter Hartnagel, Dietlinde Jakobi, Patrick Keil and Else Müller-Lorenz

Publication Date: 2011

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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 lifetime 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 lifetime 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 60 HT R (Al2O3) and G-NiCr28W (Cr2O3), they were exposed in a synthetic flue gas: 5.6%O2/14.7%H2O/8.1%CO2/71.6%N2, at 1100 °C and 1200 °C for up to 504 h. Centralloy® 60 HT R, NiCr25FeAlY, G-NiCr28W and GX40CrNiSiNb 26-35 were exposed to an annealing gas: 25%H2/75%N2 with traces of O2, at 1000°C for 504 h. The exposed samples were analysed by TG, SEM/EDX and GI-XRD.

Key words: Gas burners, annealing, flue gases, nitrides, alumina formers, chromia formers