Abstract
Intermetallic compounds, especially aluminides, show good high-temperature strength, oxidation resistance, high melting points, and thus have received considerable attention as potential substitutes for superalloys in high-temperature applications. Aluminides are especially interesting because they are stable up to the critical temperature of ordering, which is close to the melting temperature. In the Al-Ni system, the most studied intermetallics are Ni3Al, NiAl and NiAl3. In the presented study, Al and Ni powders were mixed together with Al2O3 in various proportions to produce dense coatings by low-temperature cold spraying. Two types of post-deposition treatments were applied to produce aluminides, namely furnace heating and resistance spot welding. The former caused a long time diffusion while the latter a self-propagating high temperature synthesis. Both heating methods enabled formations of intermetallic phases. However, the furnace heating provides high porosity. The microstructure of the samples was analyzed by SEM (scanning electron microscope), EDS (energy dispersive X-ray spectroscopy) and XRD (X-ray diffraction) together with microhardness measurements.
Highlights
Stoichiometric intermetallic compounds have been drawing the attention of researchers for a long time because of the unique combination of physical and mechanical properties, different from those of the constituent metals
These atoms occupy strictly defined positions in the crystal lattice, maintaining this long-range order up to the so-called critical temperature of ordering. These differences in the structure of intermetallic phases are responsible for their unique properties, which are a combination of the properties of conventional metals and ceramics [1]
All examined coatings had considerable density and thickness increasing with the increase of aluminium content in feedstock powder
Summary
Stoichiometric intermetallic compounds have been drawing the attention of researchers for a long time because of the unique combination of physical and mechanical properties, different from those of the constituent metals. Unlike conventional metals and alloys based on relatively weak metallic bonds, the atoms forming intermetallic phases are connected by strong directional covalent bonds. These atoms occupy strictly defined positions in the crystal lattice, maintaining this long-range order up to the so-called critical temperature of ordering. These differences in the structure of intermetallic phases are responsible for their unique properties, which are a combination of the properties of conventional metals and ceramics [1]. A very interesting advantage is their additional ability to sustain strength and stiffness at elevated temperatures [4]
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