Hot corrosion of atomized iron aluminides doped with boron and reinforced with alumina

The hot corrosion resistance of sprayed and atomized Fe–40 at.% Al, Fe40Al+0.1B and Fe40Al+0.1B+10Al2O3 intermetallic materials have been evaluated in NaVO3 at 625 and 700°C using polarization curves and linear polarization resistance measurements. Also, the results were supported by X-ray diffractometry and electron microscopy studies. The tests lasted 10 days. At 625°C, the Fe40Al+0.1B+10Al2O3 material exhibited the lowest corrosion rate, whereas the Fe40Al had the highest corrosion rate. At 700°C the three materials exhibited erratic behavior during the first 100 h, and after this all the intermetallics had the same corrosion rate. However, the corrosion rate was higher at 625 than at 700°C. The results are discussed in terms of an electrochemical mechanism, the establishment of an Al2O3 layer, which is more protective in the Al2O3-containing aluminide and seems to increase its protectiveness as the temperature increases from 625 to 700°C.