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Abstract: In this paper, the cyclic oxidation test of intermetallic coatings with iron and nickel aluminium is presented. The oxidation behavior of coatings strengthened by a fine dispersive Al2O3 was investigated in aggressive gases for exposure times of up to 500h. The surfaces of the composite coatings after the corrosion test in air were analyzed by light and scanning microscopy observation. An analysis of the corrosion products’ phase composition was conducted by an X-ray diffraction method. The results obtained from the presented investigations enable the elaboration of the two models of the growth of corrosion products on the intermetallic coatings strengthened by a fine dispersive Al2O3, first, on the coating with FeAl phase and second on the coating with NiAl intermetallic phase. The results show that the composite, thermally sprayed coatings have very good high-temperature corrosion resistance. [Copyright &y& Elsevier]

Abstract: The cyclic corrosion behavior of coatings with FeAl intermetallic matrix was investigated in agressive gases for exposure times of up to 500h. The composite coatings strengthened by a fine dispersive Al2O3 were thermally sprayed by HVOF method in Jet Kote 2 system. One portion of intermetallic coatings was sealed with an inorganic phosphate seal. The surfaces of HVOF sprayed coatings after a corrosion test were subjected to observation. A kinetics test was carried out by periodic method. Mass changes of the studied coatings during the corrosion test are presented. The surfaces of the composite coatings after the corrosion test in aggressive environments were analyzed by scanning microscopy observation. The results show that an adherent alumina scale and iron oxide layers were formed on all studied coatings. A stable α-Al2O3 phase on the surface of the studied coatings ensure high oxidation resistance. The corrosion rate is controlled by diffusion of corrosion products in the channels of oxide layer. An analysis of the corrosion products’ phase composition was conducted by an X-ray diffraction method. The growth of corrosion products on the thermally sprayed coatings during the corrosion test and the chemical reactions between the corrosion products and aggressive environments are presented. All the results confirm good heat proofness of HVOF sprayed coatings with an intermetallic FeAl matrix. [Copyright &y& Elsevier]

Abstract: The process of obtaining cast aluminium composite of dispersive structure and hybrid reinforcement has been presented in the article. An Aluminium alloy (AlMg2) was modified with a powder mixture which, when in reaction with aluminium, reinforced the matrix with intermetallic phases and aluminium oxide. According to the technological conception, an assumption was made, that the cast composites would be produced in technological procedure shown in Fig. 1. The reinforcing phases were using Fe–Ti–Al powder mixtures with aluminium oxide formed in a self-propagating high-temperature synthesis (SHS). The structure and phase composition of the composite powder used for the matrix alloy modification are shown in Fig. 2. A composite alloy Al–FeAl–TiAl–Al2O3 was produced by casting method (gravity casting, mechanical mixing) after which its structure was determined. It was assumed that the final product of the applied production process will be an aluminium composite with hybrid reinforcement, consisting of Fe–Al and Ti–Al intermetallic phases and aluminium oxides. Optical microscopy, electron scanning microscopy and X-ray phase analysis were used to characterize the microstructure of the composites produced. Presence of aluminium, Al3Ti and Al13Fe4 phases and dispersed Al2O3 was confirmed in the composite by XRD method. The dispersion structure and phase composition of the composites are presented in Figs. 3–6. The composites formed in an in situ reaction constitute a newer generation of casts, in which dispersion reinforcement is obtained in the form of intermetallic and ceramic phases coherent with the matrix, very often below 1μm in size. The designed process allows for the structure modification of the applied casting aluminium alloys in different technological variants. [Copyright &y& Elsevier]