Primary microstructure characterization of Co-20Ni-9Al-7W-3Re-2ti superalloy

The characterization of the primary microstructure of the new Co-based superalloy of Co-20Ni-9Al-7W-3Re-2Ti type was shown in this article. The investigated alloy was manufactured by induction melting process from pure feedstock materials. The fundamental technological problem related to Co-Al-W-X multicomponent alloys' casting process is a strong susceptibility to interdendritic segregation of alloying elements, especially tungsten and rhenium. The performed analysis revealed that the observed effect of alloying elements segregation is detectable and much stronger than for Co-9Al-9W and Co-20Ni-7Al-7W alloys, related to titanium, nickel and aluminium migration to inter-dendritic spaces. Consequently, the tungsten concentration gradient between dendritic and interdendritic zones is higher than for Co-9Al-9W and Co-20Ni-7Al-7W alloys. The same situation is in the case of rhenium and cobalt, but Co's concentration in the interdendritic zone is only slightly lower.

Grinding Kinetics Study of Tungsten Ore

The European Commission (EC) maintains the consideration of tungsten as a critical raw material for the European industry, being the comminution stage of tungsten-bearing minerals an essential step in the tungsten concentration process. Comminution operations involve approximately 3–4% of worldwide energy consumption; therefore, grinding optimization should be a priority. In this study, the grinding behavior of tungsten ore from Barruecopardo Mine (Salamanca, Spain) is analyzed. A protocol based on Austin’s methodology and PBM is developed in order to study the influence of operational and geometallurgical variables on grinding kinetics. In addition to the kinetic parameters, the breakage probability (Si) and breakage function (Bij) is determined. The selection function was formulated for the Barruecopardo Mine with respect to the mill speed.

The Analysis of Resistance to Brittle Cracking of Tungsten Doped TiB2 Coatings Obtained by Magnetron Sputtering

In this work, the authors present the possibility of characterization of the fracture toughness in mode I (KIC) for TiB2 and TiB2 coatings doped with different concentration of W (3%, 6% and 10%). The Young’s modulus, hardness and fracture toughness of this coatings are extracted from nanoindentation experiments. The fracture toughness was evaluated using calculation of crack length measurement. An important observation is that increasing tungsten concentration in the range 0–10% changes the microstructure of the investigated coatings: from columnar structure for TiB2 coating to nano-composite structure for Ti-B-W (10%) coating. It can be concluded that doping with concentration 10 at.% W causes an increase of the fracture toughness for the tested coatings.

WxNbMoTa Refractory High-Entropy Alloys Fabricated by Laser Cladding Deposition

WxNbMoTa refractory high-entropy alloys with four different tungsten concentrations (x = 0, 0.16, 0.33, 0.53) were fabricated by laser cladding deposition. The crystal structures of WxNbMoTa alloys are all a single-phase solid solution of the body-centered cubic (BCC) structure. The size of the grains and dendrites are 20 μm and 4 μm on average, due to the rapid solidification characteristics of the laser cladding deposition. These are much smaller sizes than refractory high-entropy alloys fabricated by vacuum arc melting. In terms of integrated mechanical properties, the increase of the tungsten concentration of WxNbMoTa has led to four results of the Vickers microhardness, i.e., Hv = 459.2 ± 9.7, 476.0 ± 12.9, 485.3 ± 8.7, and 497.6 ± 5.6. As a result, NbMoTa alloy shows a yield strength (σb) and compressive strain (εp) of 530 Mpa and 8.5% at 1000 °C, leading to better results than traditional refractory alloys such as T-111, C103, and Nb-1Zr, which are commonly used in the aerospace industry.

Фазовый переход металл--диэлектрик в тонких пленках диоксида ванадия, легированного вольфрамом

The electrical conductivity of thin polycrystalline V_(1 – _ x )W_ x O_2 has been studied in a wide temperature range, which covers the regions of both the metallic and insulator phases. An increase in the tungsten concentration is shown to shift the metal–insulator phase transition toward lower temperatures, while the temperature range of the coexistence of the phases monotonically increases as the impurity concentration increases. The temperature dependence of the conductivity of the insulator phase of V_(1 – _ x )W_ x O_2 is explained using the hopping conduction model that takes into account the influence of thermal vibrations of atoms on the resonance integral. Parameter ε in the dependence on the level of doping VO_2 has been calculated.

TUNGSTEN-DOPED TiO2 NANOLAYERS WITH IMPROVED CO2 GAS SENSING PROPERTIES FOR ENVIRONMENTAL APPLICATIONS

Tungsten-doped TiO2 gas sensors were successfully synthesized using sol–gel process and spin coating technique. The fabricated sensor was characterized by field emission scanning electron microscopy (FE-SEM), ultraviolet visible (UV–Vis) spectroscopy, transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Gas sensing properties of pristine and tungsten-doped TiO2 nanolayers (NLs) were probed by detection of CO2 gas. A series of experiments were conducted in order to find the optimum operating temperature of the prepared sensors and also the optimum value of tungsten concentration in TiO2 matrix. It was found that introducing tungsten into the TiO2 matrix enhanced the gas sensing performance. The maximum response was found to be (1.37) for 0.001[Formula: see text]g tungsten-doped TiO2 NLs at 200[Formula: see text]C as an optimum operating temperature.