Fabrication and properties of Fe3Al–Al2O3 graded coatings

Fe3Al intermetallic–Al2O3 ceramic graded coatings were produced by plasma spray. The microstructure and composition distribution were studied by techniques including metallurgical microscope, SEM, XRD and electron probe. The adhesive strength, micro-hardness and thermal-shock resistance of the coatings were also tested. The results showed that although the compositions of graded coatings were designed gradient transition, the composition and structure varied continuously and there were no abrupt structure changes and macro-interfaces. The structure of graded coatings exhibited macro-inhomogeneity and micro-continuity. The gradient distribution of coating composition improved adhesive strength and thermal-shock resistance of the coatings. The highest micro-hardness of coatings was obtained in the composition area of containing 75 wt.% Al2O3. The weakest point of the substrate–coating system was the interface between the substrate and the coating.