Papers by Keyword: Tantalum Carbide

Abstract: In this study, mixtures of 25 wt.% of tantalum carbide (TaC) and iron (Fe) or nickel (Ni) powders were mechanical alloyed against time in order to investigate the interactions between the reinforcement (harder TaC particles) and surrounding ductile metallic matrixes (Fe and Ni). After mechanical alloying, apparent densities and particle size and distribution (PSD) of the powders were measured and morphological observations were realized via scanning electron microscopy (SEM). X-ray diffraction (XRD) was applied for phase analysis and with increasing mechanical alloying time certain shifts were observed for the two theta values of the samples. These data used for characterization of strain rates and crystallite sizes by fundamentals parameters approach applied with Lorentzian function and Williamson-Hall plot analysis.

Abstract: Fe-C-Ta-Cr-Ni alloy powder in diameter of 32-53 μm made by argon atomization was low-pressure plasma sprayed to produce high Cr-Ni cast iron base deposits with finely dispersed tantalum carbide particles. The as-sprayed deposit formed on a water-cooled substrate consisted of γFe, αFe and carbide. The fine precipitates of approximately 0.1 μm in the as-sprayed deposit formed on a water-cooled substrate were carbide. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The hardness of deposit decreases with increasing heat treatment temperature. The wear resistance of as-sprayed deposit formed on a non-cooled substrate was higher than that of the deposit heat-treated at 1273 K. The as-sprayed deposit and deposit heat-treated at 1273 K hade higher wear resistance than a commercial stainless steel.

Abstract: Tantalum and hafnium carbides are classified as Ultra High Temperature Ceramics (UHTC) because of their extreme melting temperatures (above 3900°C). Therefore, these materials can safely operate in the range of temperature that any other materials could hardly exist. However, these applications can be strongly restricted due to (1) processing difficulties and (2) low fracture toughness. In this work, to address these two difficulties we have used two additives, which are multi-walled carbon nanotubes (CNTs) and molybdenum disilicide (MoSi₂). The CNTs were added aimed to improve the fracture toughness of the composites, and the MoSi₂ to facilitate sintering. Application of such a sintering aid, add to the novel SPS technique, allowing quick processing at relatively lower temperature, results in (1) fully densified specimens (> 99%) and (2) well-surviving CNTs after sintering. Moreover, microstructural analysis points out fair-enough dispersion of the CNTs within the ceramics particles, in both the green and sintered bodies. Also the specimens phase characterization shows inter dissolution of TaC and HfC and formation of binary carbides solid solution.

Abstract: The mechanical properties of a SiC-fiber/copper matrix composite, reinforced with SCS-0 SiC-fibers ( 140µm, Specialty Materials), can significantly be increased by applying a Ti-Ta-C multilayer between fiber and matrix. This interlayer is deposited with a magnetron sputter device directly on the single fibers. By changing the deposition parameters of this sputter process the Ti-Ta-C interlayer can be optimized regarding fiber strength and fiber/matrix adhesion. Experiments with different deposition pressures, bias voltages and layer thickness’ were performed to increase the bond strength and the ultimate tensile strength when compared to the Ti-Ta-C reference sample.

Abstract: Four cast superalloys, Fe-base and (Fe,Ni)-base alloys, all containing 30%Cr and 0.4%C, were elaborated with addition of 3% and 6% of tantalum. Their oxidation behaviours were studied at 1000, 1100 and 1200°C during 50 hours. The oxidized surfaces of the samples were quantitatively characterized by measurements of thicknesses and surface fractions of internal oxides. The thermogravimetry files were treated according to the {m×(dm/dt) = Kp - Kv×m} equation, to obtain simultaneously the parabolic constant and the chromia volatilization constant. The internal tantalum oxides are more present in the Fe-base alloys and the carbide-free zones are less developed for the (Fe,Ni)-base alloys than for the others. The Fe-base alloys oxidize faster than the (Fe,Ni)-base and Ni-base alloys. The comparison with the corresponding Ta-free ternary alloys shows that the presence of Ta tends to accelerate the oxidation.

Abstract: This work presents the investigation results of laser remelting and alloying especially the laser parameters and its influence on the structure and properties of the surface of the 32CrMoV12-28 hot work steel, using the high power diode laser (HPDL). As a result structure changes in form of fragmentation were determined. The reason of this work was to determine the optimal laser treatment parameters, particularly the laser power to achieve good layer hardness for protection of this hot work tool steel from losing their work stability and to make the tool surface more resistant to action in hard conditions. For alloying the tantalum carbide, tungsten carbide and vanadium carbide powders were used. For investigations hardness measurements of the different remelting areas were performed. The remelted layers which were formed in the surface of investigated hot work steel were examined metallographically and analyzed using light and electron microscope. Three phases of carbides, TaC, VC and WC, were observed.