Performance of Alumina-Forming Austenitic Steels, Fe-Base and Ni-Base Alloys Exposed to Metal Dusting Environments

In high carbon activity environments, metals can suffer from catastrophic disintegration, or “metal dusting,” forming metal-rich particles dispersed in a carbon deposit.  Protection against such degradation relies on the formation of an external, protective oxide layer, in general, a Cr-rich oxide. The tendency is to use Ni-base alloys, rather than Fe-base alloys, largely because of the slower inward diffusion of C for Ni-base alloys.  However, in atmospheres with high water vapor contents, the relative performance can change and Fe-base alloys can be more resistant than Ni-base alloys.  Alumina also is a very effective barrier against C diffusion and it has the advantage of being more stable in the presence of water vapor.  Several commercial Ni-base alloys containing Al have been developed for these environments.  New high-strength, alumina-forming austenitic (AFA) stainless steels have the possibility of replacing Ni-base alloys for some chemical process industry applications.  Thus, the aim of this work is to study the effect of water vapor concentration, carbon activity and total pressure on the metal dusting resistance of various Ni-base, Fe-base and AFA alloys.