Optical microscopy as a simple method for analysis of boiler tube failure

  • Milan Jovanović Department of Materials Science, Institute of Nuclear Sciences “Vinča”, University of Belgrade, POB 522, 11001 Belgrade, Serbia
  • Zoran Mišković Department of Materials Science, Institute of Nuclear Sciences “Vinča”, University of Belgrade, POB 522, 11001 Belgrade, Serbia
  • Vesna Maksimović Department of Materials Science, Institute of Nuclear Sciences “Vinča”, University of Belgrade, POB 522, 11001 Belgrade, Serbia
  • Ivana Cvijović-Alagić Department of Materials Science, Institute of Nuclear Sciences “Vinča”, University of Belgrade, POB 522, 11001 Belgrade, Serbia
Keywords: Boiler tube, Austenite, Bainite, Widmanstätten ferrite, Overheating, Failure

Abstract

A severely damaged low carbon steel boiler tube was the object of this investigation. Detailed microstructural characterization was performed by optical microscopy, whereas scanning electron microscopy (SEM) was applied only in a few cases. Results show that a variety of microstructures was formed in the material of the damaged boiler tube during its exploitation. The failure of the tube is the result of very inhomogeneous overheating. The side of the boiler tube toward fire (F) was exposed to high overheating temperature, which in some locations was well above the A3 transformation temperature. The side toward boiler (BL) was subjected to lower temperatures, i.e. in the region mostly between A1 and A3 temperatures. Variations in temperatures and cooling rates, which resulted in microstructural inhomogeneity, are the main cause for the formation and multiplication of stresses leading to the rupture of the tube.

Author Biography

Milan Jovanović, Department of Materials Science, Institute of Nuclear Sciences “Vinča”, University of Belgrade, POB 522, 11001 Belgrade, Serbia

Department of Materials Science

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Published
2020-01-14
Section
Djordje Drobnjak - Memorial Issue