Nano-sized carbon filament formation during metal dusting of stainless steel

The carburization and the formation of nano-sized carbon filament or tube on 304 stainless steel (SS) in a reducing atmosphere were investigated. The 304 SS was first pre-carburized using pack cementation process. After removing the scales formed on the surface of the pre-carburized specimens, they were then exposed to a mixed gas of CO/CO2=100/1, and at 500 and 700 °C, respectively, for 30 h. The surface morphology, microstructure, chemical composition and crystal structure of carbon filaments or tubes formed were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA) and Raman spectroscopy. The experimental results showed that, in reducing mixed CO/CO2 gases, metal dusting occurred resulting in the formation of Fe/Ni particles. The disintegrated metal particles catalytically promoted nano-sized carbon filament or tube formation.