Long-term corrosion behavior of FeCr(Al, Ni) alloys in O2 + H2O with KCl(s) at 600 °C: Microstructural evolution after breakaway oxidation
Vicent Ssenteza, Johan Eklund, Sedigheh Bigdeli, T. Jonsson
Abstract
The microstructural evolution of the oxide scales formed on FeCr(Al,Ni) alloys after breakaway oxidation was studied in 5% O2 + 20% H2O + N2 (Bal) + KCl(s)/KCl(g) at 600 °C for 168, 1000 and 8000 hours. The SEM/EDS, SEM/EBSD and XRD investigation show that all alloys experience breakaway oxidation and form multi-layered scales. Experimental results, thermodynamic modelling and kinetic simulations show that FeCrAl and FeCrNi alloys form chromium-rich spinel oxide in inward-growing scales which transform into a protective corundum-type oxide as the oxidation progresses, while FeCr alloy experiences fast oxidation and maintains a non-protective spinel oxide/internal oxidation after long exposures.