high temperature oxidation behavior of hp-nb alloy

Reformer tubes are used in the steel industry in the regeneration unit. due to the high temperature required to produce reduction gases, these tubes experience a high temperature gradient and eventually more prone to oxidation. in the present study, in order to understand the effect of the real condition on the function of parts and study high temperature microstructure characteristics of the tube reformers some samples were extracted from the hp40 alloy which was out of line service. optical microscopes, scanning electron, eds and xrd were used to investigate the microstructure of hp40. the formation of the protective layer on the surface of the steels was confirmed by the analyzes, however, according to the working conditions, after some time the oxide layer continues to dissolve and oxidize the steels.