The Effect of the Third Element Cr on Oxidation Behavior of Fe-xCr-10Al (at.%) Alloys at 900°C

Alloys Fe-(0, 5, 10)Cr-10Al (all in at.%) were oxidized at 900 o C in 1 atm oxygen to study the effect of Cr addi- tions on the oxidation behavior. The oxidation kinetics was recorded with a thermal microbalance. The morphologies and microstructures of the oxide scales were examined using SEM, EDS, and XRD. Fe-10Al developed an Al2O3-rich scale during the initial stage of oxidation, and a non-protective scale containing oxides of Fe and Al formed. Mixed oxides of Al and Fe formed firstly on Fe-5Cr-10Al, but an externally dense and continuous Al2O3-rich scale formed. The initially formed Fe oxides were locally reduced to Fe-rich particles. Fe-10Cr-10Al formed an Al2O3-rich scale from the onset of oxidation and this slowly growing scale was protective up to 50 h. The Cr additions to Fe-10Al were beneficial for re- straining the oxidation of Fe, but that did not promote the transition from metastable Al2O3 to � -Al2O3.