Relationship of Carbon Crystallization to the Metal-Dusting Mechanism of Nickel

Raman scattering and X-ray diffraction (XRD) were used to study the mechanism of metal-dusting corrosion of nickel and Alloy 601. The Raman bandwidths and the relative intensities of the 1330- and 1580-cm - 1 bands are related to the crystallinity and defect structure of coke. Both Raman and XRD analyses suggest that there is a relationship between metal dusting and the catalytic crystallization of carbon. Coke cannot crystallize well by deposition from carburizing gases at low temperature without catalytic activation because of its strong C−C bonds and high melting temperature. Participation of nickel during the coke-crystallizing process tends to improve the crystallinity of the coke. At the same time, nickel particles are liberated from metal. A decrease in free energy from highly disordered carbon to well-crystallized carbon is the driving force of metal dusting.