HIGH TEMPERATURE CORROSION OF BURNER TUBE ALLOYS EXPOSED TO FLUE GAS AND REDUCING ATMOSPHERE USED FOR ANNEALING – A LABORATORY STUDY

摘要

A demand for greater throughput and quality causes a ditto demand for higher temperatures in theannealing furnaces. The burners used for this application are already operating close to their uppertemperature limit. This causes increased wear of the materials used in the burners and shortens theirlifetime considerably. The wear is caused by several factors such as creep and high temperaturecorrosion. The burners are in contact with two distinct types of atmospheres, the flue gas inside theburner 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 Cr_2O_3 formers. In thisstudy the high temperature corrosion behaviour in flue gas as well as annealing gas of two such alloyshas been investigated on lab scale.The alloys involved were spun cast 60 HT R (Al2O3) and G-NiCr28W (Cr_2O_3), they were exposed in asynthetic flue gas: 5.6%O_2/14.7%H_2O/8.1%CO_2/71.6%N2, at 1100 ℃ and 1200 ℃ for up to 504 h.Centralloy? 60 HT R, NiCr25FeAlY, G-NiCr28W and GX40CrNiSiNb 26-35 were exposed to anannealing gas: 25%H2/75%N2 with traces of O_2, at 1000℃ for 504 h. The exposed samples wereanalysed by TG, SEM/EDX and GI-XRD.