High-temperature oxidation of Fe40Al coatings obtained by HVOF thermal spray

The objective of the present work is to provide insight into the high-temperature performance of iron aluminide intermetallic coatings, sprayed using high velocity oxygen fuel. Isothermal oxidation experiments were completed at 900, 1000 and 1100 °C and the cross sections and free surfaces of the coatings were characterized after 4, 36 and 72 h of exposure. The present results show differences in the oxidation behaviour of the coatings at those temperatures and they are specially remarkable when compared to bulk materials. For example, while at 1000 and 1100 °C where bulk FeAl presents a compact alumina layer, the coatings failed to reveal the presence of the stable α-Al2O3 phase, and an accelerated corrosion was observed leading to detachment from the substrate. On the basis of these results, the reasonable good performance exhibited at 900 °C indicates this could be the border line of the oxidation resistance for those coatings.