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 + 10Al(2)O(3) intermetallic materials have been ev aluated in NaVO3 at 625 and 700 degreesC using polarization curves and line ar polarization resistance measurements. Also, the results were supported b y X-ray diffractometry and electron microscopy studies. The tests lasted 10 days. At 625 degreesC, the Fe40Al + 0.1B + 10Al(2)O(3) material exhibited the lowest corrosion rate, whereas the Fe40Al had the highest corrosion rat e. At 700 degreesC the three materials exhibited erratic behavior during th e 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 degreesC. The results are discussed in terms of an electrochemical mechanism, the est ablishment of an Al2O3 layer, which is more protective in the Al2O3-contain ing aluminide and seems to increase its protectiveness as the temperature i ncreases from 625 to 700 degreesC. (C) 2001 Elsevier Science B.V. All right s reserved.