J. M. Guilemany, N. Cinca, J. R. Miguel, Thermal Spray Center. University of Barcelona, Barcelona, Spain
Intermetallics are specially interesting compounds for their excellent corrosion and oxidation resistance owing to their ordered lattice which provides them a high structural stability even at elevated temperatures. The aluminides are specially promising for industrial applications where a high resistance/weight ratio and hot corrosion resistance is required. The aim of the present study is to study the performance of iron aluminide intermetallic coatings sprayed by means of High Velocity Oxygen Fuel technique at high temperature environments. The isothermal tests have been undergone at 900 and 1100ºC and the study of cross sections and free surfaces after several times has been carried out.There is a remarkable difference in the oxidation behaviour and kinetics compared to bulk materials owing to not observable formation of high temperature stable alumina phase at 1100ºC, where an accelerated corrosion has undertaken due to the defect concentration. It has been proposed a model for scale growth. Thus, only at 900ºC a good service performance has been assessed. In this case, it could be defined as a parabolic growth as observed for bulk FeAl in contrast to the breakaway oxidation produced at 1100ºC.
Summary: The high temperature oxidation behaviour of Fe-40%at.Al has been evaluated for different times at 900 and 1100ºC. After structural characterization, it has been concluded that these coatings may assure a good service performance at 900ºC, while breakaway oxidation is observed at 1100ºC.
