Papers by Keyword: NiAl Intermetallic Compound

Abstract: In this study the influence of the TiB₂, ZrB₂, and CrB₂ additives into NiAl-intermetallics on their wear behavior under friction conditions at the high temperature in the pair with steel has been investigated. It was shown, that the borides additives have influenced on the wear mechanism, significantly increasing the wear resistance of composite coatings pointed out. Among the coatings studied the NiAl-15 wt. % CrB₂ coating showed the best result.

Abstract: NiAl and Ni₃Al intermetallic compound claddings are prepared by argon arc cladding technology on the 16Mn steel substrate. These claddings were oxidized for 100 hours at 850 and the oxide quality of each sample was recorded every 10 hours. The results show that the NiAl and Ni₃Al claddings have homogeneous structure and few defects, and form excellent metallurgical bonding with the matrix. The oxidation kinetics results show that, the oxidation weight gain rate of NiAl was more stable than Ni₃Al and tended to zero earlier. Oxide layer spallation of Ni₃Al cladding was more serious than that of NiAl cladding. Thus, NiAl argon arc cladding has the more excellent high temperature oxidation properties than Ni₃Al argon arc cladding.

Abstract: We focused on the surface reinforcement of Al casting alloys with Ni-Al intermetallic compounds by in-situ combustion reaction to improve the surface properties of Al casting components. Microstructure and phase formation behavior of Ni-Al based intermetallic compounds synthesized by combustion reaction were investigated in terms of thermal and phase analysis using scanning electron microscope(SEM) equipped with energy dispersive x-ray spectrometer (EDS) and x-ray diffractometer(XRD) in Ni-Al intermetallic compounds. Three kinds of nickel aluminides, NiAl3, NiAl and Ni3Al, were synthesized by emission heat from the Al molten metal in order to form a coating layer of intermetallic phase simultaneously on the solidifed Al alloy surface. The synthesized shapes and microstructures of nickel aluminides were varied by casting temperature, Si contents, and the mixing ratio of elemental powders. The synthesized reaction products formed in nickel aluminides were observed to be different depending on the mixing ratio of elemental powders. The reaction layer of about 25
m thickness was formed at the interface, and it mainly consisted of NiAl3 phase by the reaction between liquid molten Al alloy and solid Ni powders in green compact. With this information, we successfully produced a coating layer of Ni3Al intermetallic compound onto the casting Al alloy surface using molten metal heat without any additional process. These findings led us to conclude that a near-net shaped nickel aluminide coating layer can be formed using this unique process.

Abstract: Mechanical properties of two stoichiometric NiAl intermetallic alloys processed by hot hydrostatic extrusion were investigated. The ingots for extrusion process were produced both by casting and by powder metallurgy route in which the self-sustained high-temperature synthesis (SHS) of elemental powders was initialized by the process of extrusion itself. Elastic anisotropy of the obtained products were determined using a resonant ultrasound spectroscopy (RUS) in measurements of the elastic constants. The anisotropy of plastic properties was estimated from uniaxial compression tests on specimens cut off from the material in the main directions of previous deformation. An acoustic emission (AE) method of monitoring of the microcracking process in the material was used for estimation the role of cataclastic mechanism of deformation. The effect of annealing of extruded materials on their plastic behavior was roughly investigated.