Metal dusting of alloys

A number of investigations have been reported in the literature on the metal dusting of Ni based alloys. The present discussion focuses on studies 

11 Metal dusting corrosion of Inconel 600 at 750°C for 160 hours showing localized corrosive attack, regions protected by surface oxide, metal dust within carbon deposit, graphite intrusion into alloy, and M3C2 carbide precipitates in the alloy subsurface region (adapted from ref. 16). 

M3C2 type carbide precipitates of varying sizes. The M in the carbide formula consists of about 48 wt% Cr, 45% Ni and 7% Fe. The alloy next to the carbide is severely depleted in Cr, with a composition of 84% Ni, 6% Cr and 10% Fe. 

The increased rate of metal dusting with temperature in regime I can be generally attributed to faster kinetics of the different sequential steps in 

Alloy name Temperature (°C) Maximum pit depth (pm) Pit diameter (pm) Pit density (number of pits/cm ) 

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If printing on paper, wrappings, etc., is to be tested for powdered metals, dusts of alloys, etc., it is enough to place a drop of phosphomolybdic acid solution on the paper and to note the formation of a blue coloration. 

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