High temperature corrosion behaviour of wire arc sprayed Fe based coatings

Fe–Cr–Al and Fe–Cr–Al–B cored wires were designed and produced to deposit protective coatings for components used in high temperature environments by wire arc spraying technique. The microstructure, microhardness and high temperature corrosion behaviour of the new coatings were investigated in comparison with Fe–Cr coating and with commercial Fe–Cr–Al coating. All coatings presented lamellar microstructures with oxide inclusions. The new Fe–Cr–Al–B coating showed the fewest oxide inclusions among all the coatings. The microhardness of Fe–Cr–Al coating was quite low, while the microhardness of Fe–Cr–Al–B was found to be higher. Thermogravimetric analysis was used to evaluate the high temperature corrosion behaviour of the coatings in a molten salt (Na₂SO₄–25%K₂SO₄) environment at 650°C under cyclic conditions. The results showed that the new Fe–Cr–Al–B coating exhibited the best high temperature corrosion behaviour.