Diffusion and plasma oxidation mechanism of Fe–Al coatings

Abstract

Al coatings were deposited using a pure Al target directly onto pure iron substrates at different temperatures by double glow discharge technique. Then, the Fe-Al coatings were plasma oxidised at 580uC. The results indicated that the aluminide layer was nanocrystalline with many crystal defects after the aluminising process. The oxidation kinetics showed a two-stage behaviour. The energetic O ions with higher driving force diffused into the coatings at the beginning of the oxidation. Then, O ions diffused via short circuit diffusion caused by the existence of large amounts of grain boundaries and crystal defects. After oxidation, a-Al 2 O 3 , c-Al 2 O 3 and Fe 2 O 3 phases were detected. Large amount of voids filled with oxide ions were formed at the outermost aluminide layer owing to the different intrinsic diffusivities of Fe and Al.

Laser alloying with Fe–B4C–Ti on AA6061 for improved wear resistance

“…According to the studies of Fe–Al system, intermetallic compounds such as Fe 4 Al 13 (FeAl 3 ), FeAl, Fe 3 Al, Fe 2 Al 5 , FeAl 2 , etc. can be generated spontaneously owing to the low Gibbs free energy [16]. Grin et al [17] pointed out that although FeAl 3 was more frequently used for the composition of the θ -phase in Fe–Al intermetallic, the actual stoichiometry was Fe 4 Al 13 .…”

Study of Nanostructured CeO2 Coatings on Superalloy

“…3,4 Rare earths' oxide coatings have the advantage of not affecting adversely the mechanical properties of the alloy and the potential of being used on metallic components in service and exposed to high-temperature oxidising environments. Nanostructured coatings have been identified as potential materials for providing good resistance against high-temperature oxidation and hot corrosion [5][6][7][8][9][10][11][12][13][14] as compared to conventional coatings due to the formation of dense, continuous, non-porous and adherent alumina and/or chromia scales over the coatings. [15][16][17] The size effect of nanostructured coatings facilitates the enhanced diffusivity of atoms to form the continuous protective scales, which is normally discontinuous in the conventional coatings as reported in the literature.…”