Failure analysis of convection section tube in an ethylene cracking furnace due to metal dusting

Abstract

To study the failure in the convection section tubes of an ethylene cracking furnace, macroscopic inspections, chemical composition analysis, metallographic microscopy, hardness testing, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis are performed. The experiments confirmed the reason for metal dusting occurrence of 304H austenitic stainless steel that the inner wall Cr2O3 protective film was destroyed by overheating. There were dense circular corrosion pits on the fire side inside the furnace tubes, loose metal oxides and carbide particles were filled in the corrosive pits. Severe carburization occurred on the surface of the pits, the furnace tube experienced metal dusting. The metal dusting resulted in the decomposition of the surface layer of the metal alloy into metal particles and graphite to thin the wall thickness. Then the furnace tube cracked because of the stress concentration appeared in the furnace tube with reduced wall thickness. Finally, some suggestions and countermeasures on the failure of metal dusting of the furnace tube were proposed.