Failure analysis of conversion reactor drum by metal dusting

The catastrophic failure of a heat resistance steel conversion reactor drum was investigated. Conventional metallography and SEM were used to identify the microstructure of the samples. EDS was used for microchemical analysis. The phases produced in the drum inner surface were identified by X-ray diffraction. Average carbon content was measured using CS-analyzer equipment. Changes in mechanical properties were evaluated by Rockwell B hardness test. A complex pattern of external scaling, internal oxidation and varying extents of surface disintegration and pitting were identified as high-temperature corrosion by metal dusting. The results showed that metal dusting type III, active corrosion, had taken place in reactor. As a consequence of metal dusting, carbides had been solved and pits and holes had been formed in matrix especially along with grain boundaries. Finally, cracks which had been initiated from pits or holes broke reactor.