M. Casales

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

Abstract 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 evaluated in NaVO 3 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+10Al 2 O 3 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 Al 2 O 3 layer, which is more protective in the Al 2 O 3 -containing aluminide and seems to increase its protectiveness as the temperature increases from 625 to 700°C.

Oxidation behavior of atomized Fe40Al intermetallics doped with boron and reinforced with alumina fibers

Isothermal oxidation resistance of Fe40 (at.%) Al-based atomized and deposited intermetallic alloys has been evaluated. The alloys included Fe40Al, Fe40Al + 0.1B, and Fe40Al + 0.1B + 10Al2O3 at 800, 900, 1000, and 1100 °C. The tests lasted approximately 100 h, although in most cases there was scale spalling. At 800 and 900 °C, the Fe40Al + 0.1B alloy had the lowest weight gain, whereas the Fe40Al alloy had the highest weight gain at 800 °C (0.10 mg/cm2) and the Fe40Al + 0.1B + 10Al2O3 alloy was the least oxidation resistant at 900 °C with 0.20 mg/cm2. At 1000 °C, the Fe40Al + 0.1B alloy showed the highest weight gain with 0.12 mg/cm2 and the Fe40Al alloy the lowest. At 1100 °C, again, as at 900 °C, the Fe40Al alloy was the least resistant, whereas the Fe40Al + 0.1B alloy performed the best, but the three alloys exhibited a paralinear bahavior on the weight-gain curves, indicating the spalling, breaking down, and rehealing of the oxides. This spalling was related to voids formed at the metal-oxide interface.