Fe <sub> 3 </ Sub> Al Intermetallic Compounds Sulfide Corrosion Research

FeAl-based alloys as promising materials have numerous attractive properties for high temperature applications. The sulfuration behavior corrosion is important in the applications. The aim on studies o f Fe-Al of sulfuration behavior is to analysis and investigate microstructural by testing methods, understand the essence of sulfuration fully. The sulfuration mechanisms of Fe-Al intermetallics are discussed by investigating the sulfuration behavior of materials.The results showed that the dynamic curve of Fe28Al sulfuration behavior satisfied parabolic law. In the temperature of 600℃ to 800℃, Fe28Al has good sulfuration-resistance ;however, the oxidation film increase too much at 1000℃, pore and crack are formed in short time, resulting in sulfide formation, the ability of sulfuration-resistance decreased. The rate of sulfuration is more quickly than that of oxidation. Fe28Al has good oxidation resistance properties in the oxidation corrosion conditions. Temperature and corrosion atmosphere have effect on the corrosion resistance of Fe28Al.Compared with oxidation mechanism, the corrosion mechanism of Fe28Al in SO2+N2 mixture was analyzed; the rate of interface reaction is prominent factor in the initial period. Simultaneously Fe28Al alloys absorbed gas molecules, Al2O3 film is formed firstly. The oxidation film is thin and density, good bonding with the matrix, good stability, easy deformable, so the stress is a little. S can diffuse slowly the oxidation film, no sulfide and oxidation has formed in the surface of matrix. Diffusion process play a rule in the corrosion lately. With the time prolong and temperature increasing, oxidation film increases. Owing to the metal ion moving b y t he c oncentration g rade, d iffusion p rocesses p lay t he more a nd more rule, and is a decisive factor in the further oxidation. In the last, Fe in the matrix diffuse outward, form co-crystal with FeS, resulting in S and metal diffusion quickly, and destroy oxidation coating, form the sulfide film. Owing to the high PB of sulfide film, sulfide film can be destroyed easily, crack formation in the intergranular, so S can diffuse into the inward along the crack, leading to inward sulfide film formation, thereby catastrophiccorrosion happened.