Study of the migration and distribution pathways of key corrosive species during high-temperature corrosion by means of atom probe tomography and δ35Cl isotope tracer

Abstract

This study investigated the migration pathways and the dominant chlorine- and alkali-induced corrosion mechanisms of Ni-28Cr-13Al-0.6B-0.5W alloy at 600ºC. The distribution of key elements (35Cl, 37Cl, Na, O, Ni, Cr, Al) at the alloy/oxide interface was analyzed by APT coupled with δ35Cl isotope labeling for tracing the competitiveness of organic chlorine and inorganic chlorine. The alloying element`s migration rate was in the order of Al > Cr > Ni > W. Cl diffused through oxide grain-boundaries as Cl- ions formed by the decomposition of sulfate-melt and corrosion in grain-boundaries was dominated by electrochemical reaction mechanisms. Na enhances the diffusion of elements by widening the grain-boundaries.