THE CORROSION AND MECHANICAL BEHAVIORS OF ALUMINIDE, FECRALY AND COCRALY COATINGS IN AGGRESSIVE ENVIRONMENTS

The mechanical and chemical behaviours of aluminide coatings applied by pack cementation, FeCrAlY coatings applied by plasma spraying and CoCrAlY coatings applied by electrodeposition were studied. The coatings were pretreated for 0.5 h in argon at 1373 K to improve the adhesion and structural homogeneity via diffusion of the elements into the substrate to some extent. In particular, the influence of the temperature on their protective behaviours was studied. Corrosion studies have been carried out between 823 and 1123 K in oxidizing-sulphidizing environments. In aggressive environments and under stress-free conditions the aluminide coatings showed the best results, probably owing to the presence of a protective oxide scale. Because of the tendency for crack formation, any applied stress will lead to cracking of the layer and the onset of severe corrosion attack. The FeCrAlY coatings showed the best protection.