On elevated temperature stability of high carbon Fe-Al alloys

Ingots of Fe-Al alloys containing 1.1 wt.% C each and 8.5, 16 and 20 wt% Al , respectively were prepared by a combination of air induction melting and electroslag remelting. These ESR ingot samples were placed in a hearth furn ace at 1273 K for 24 h and then furnace cooled to room temperature. The ESR ingots exhibited a significant amount of precipitation of Fe3AlC0.5 phase. Fe-16 wt% Al-1.1wt% C and Fe-20 wt% Al-1.1 wt% C ESR ingots exhibited coar se columnar grains along the ingot axis. No significant change in microstru cture was observed in these ingots after heat treatment. Dendritic solidifi cation was observed in ESR ingots of the Fe-8.5 wt% Al-1.1 wt% C alloy with copious precipitation of fine Fe3AlC0.5 phase in the interdendritic region . After heat treatment some coarsening of the interdendritic precipitates a nd precipitation within the dendrites was observed leading to a more homoge neous microstructure. Fe-8.5 wt% Al-1.1 wt% C alloy samples were badly oxid ized after the heat treatment. This was accompanied by significant decarbur ization in regions near the sample surfaces leading to a localised loss in hardness. It would appear from the present work that high carbon Fe-Al allo ys containing 16 wt% Al or more are resistant to oxidation and decarburizat ion. (C) 1999 Elsevier Science S.A. All rights reserved.