Addition Of Tungsten Research Articles

Role of refractory elements in near-alpha titanium alloys on high temperature mechanical properties

The effect of Tungsten (W), Tantalum (Ta) and simultaneous addition of Germanium (Ge) and Silicon (Si) on the microstructure evolution, tensile and creep properties of the near-alpha alloy Ti-5.7Al-3.9Sn-3.7Zr-0.7Nb-0.5Mo-0.35Si-0.05C have been investigated at high temperatures up to 650°C. Microstructural characterizations following solution treatment at 1050°C for 2 hours with oil quenching and aging treatment at 700°C for 2 hours followed by air cooling, highlighted that the additions of refractory elements such as W and Ta led to a decrease of both the volume fraction of the primary alpha phase (ap) and its average size. Tensile tests performed up to 650°C revealed a significant improvement in tensile strength with additions of W and Ta, even though a decrease of ductility has been also detected. Creep tests carried out at 600°C under a constant stress of 200 MPa pointed out that, refractory elements, Ge and Si have a beneficial effect on both primary and steady-state creep strain rates.

Role of tungsten modifiers in bimetallic catalysts for enhanced hydrodeoxygenation activity and selectivity

Addition of tungsten to supported platinum catalysts increased the rate of benzyl alcohol hydrodeoxygenation via a bifunctional mechanism, whereas undesirable decarbonylation was suppressed due to blocking of platinum terrace sites.

Review on In-depth Analysis of the Passive Films of W-xTi Alloys by Angle Resolved X-Ray Photoelectron Spectroscopy

Spontaneously passivated sputter-deposited W-22Ti and W-58Ti alloys showed higher corrosion resistance than those of tungsten and titanium metals in 12 M HCl solution open to air at 30°C. Average corrosion rates of W-(22-58)Ti alloys (that is, about 9.5-18.5 × 10-3 mm/y) were found to be about three and half orders of magnitude lower than titanium and even lower than that of tungsten metal. Such synergistic effect of the simultaneous additions of tungsten and titanium in the extremely high corrosion resistance properties of the sputter-deposited amorphous/nanocrystalline W-xTi alloys was investigated using angle resolved X-ray photoelectron spectroscopic (ARXPS) analyses. In-depth surface analyses of the thin passive films of the W-xTi alloys using angle resolved XPS analyses revealed that the high corrosion resistance of the amorphous/nanocrystalline W-xTi alloys is mostly due to the formation of homogeneous passive double oxyhydroxide films consisting of Wox and Ti4+ cations without any concentration gradient in-depth in 12 M HCl solution at 30°C. Consequently, titanium metal acts synergistically with tungsten in enhancing the spontaneous passivity as well as the high corrosion resistance of the sputter-deposited binary W-xTi alloys.

Stimulation of cell growth by addition of tungsten in batch culture of a methanotrophic bacterium, Methylomicrobium alcaliphilum 20Z on methane and methanol

It is carried out for researches to convert methane, the second most potent greenhouse gas, to high-value chemicals and fuels by using methanotrophs. In this study, we observed that cell growth of Methylomicrobium alcaliphilum 20Z in the batch cultures on methane or methanol was stimulated by the addition of tungsten (W) without formate accumulation. Not only biomass yield but also the total products yield (biomass and formate) on carbon basis increased up to 11.50-fold and 1.28-fold respectively in W-added medium. Furthermore, a significant decrease in CO2 yield from formate was observed in the W-added cells, which indicates that W might have affected the activity of certain enzymes involved in carbon assimilation as well as formate dehydrogenase (FDH). The results of this study suggest that M. alcaliphilum 20Z is a promising model system for studying the physiology of the aerobic methanotroph and for enabling its industrial use for methane conversion through high cell density cultivation.

The effect of tungsten content on the rolling texture and microstructure of Ta-W alloys

The effect of tungsten content on deformation texture and microstructure of Ta-W alloy is studied. It is found that the increase of tungsten content results in the strengthening of α-fiber and the weakening of γ-fiber in Ta-W alloys. The volume fraction of γ-fiber developed in Ta-10W alloy is lower than that in Ta-2.5W alloys. Meanwhile, a more significant through-thickness texture gradient is formed in Ta-10W alloy. The addition of tungsten has an important effect on the ability cross-slip of dislocations. Therefore, more dislocation loops and activated slip systems can be seen in Ta-2.5W alloy. The size of the dislocation cells in Ta-2.5W alloy is larger than that in Ta-10W alloy. As shear bands tends to appear in γ-fiber, the density of shear bands in the Ta-2.5W alloy is much higher than that of Ta-10W alloy at the same reduction strain. Meanwhile, the wavelength of the wavy shear bands in Ta-10W alloy is smaller than that in Ta-2.5W alloy. In Ta-10W alloy, new grains with Goss orientation can be seen in periodic shear bands developed in {111}<112> orientations, which is different from that in Ta-2.5W alloy.

Effect of tungsten content on microstructure and mechanical properties of PCBN synthesized in cBN-Ti-Al-W system

Polycrystalline cubic boron nitride (PCBN) compacts were prepared using the mixture of cubic BN and Ti-Al-W powders at 5.5 GPa and 1550 °C for 10 min. The influence of different Tungsten (W) content on composition, microstructure, porosity, mechanical property and cutting performance of the PCBN is investigated. The results show that, with the addition of tungsten, the cubic boron nitride (cBN) crystals are connected with each other by the new product phases TiB2, TiN, Al3Ti and W2B under the pressure of 5.5 GPa and the temperature of 1550 °C. The rod-shaped crystals in the PCBN are expanded from the surface portion of the cBN. As the W content increases, the amount of rod-shaped crystals and the length-diameter ratios decrease in the system. When the tungsten content is 6 wt%, PCBN presents the best comprehensive performance and cutting performance, the porosity, the hardness, the flexural strength and the flank wear are 0.55%, 30.71 GPa, 972.3 MPa and 292 μm, respectively.

Validation of an alloy design strategy for stable Fe–Cr–Al–Nb-X ferritic alloys using electron microscopy and atom probe tomography

The Fe–Cr–Al–Nb ferritic alloys strengthened by A2B Laves phases, with superior oxidation and corrosion resistance, are being considered for high temperature operation within fossil-fired steam power plants to increase process efficiency and reduce CO2 emissions. In this study, new sets of alloys based on Fe–30Cr–3Al–1Nb (in weight percent) were designed with (i) a high microstructural stability of Laves phase precipitates in a BCC-Fe matrix and (ii) reduced precipitate free zones along the grain boundaries, targeting an operating temperature of 700 °C. Two alloys with titanium or tungsten additions were down-selected through thermodynamic calculations with a design strategy to maximize the amount of Laves phase at 700 °C and lower the BCC solvus temperature. To validate this design strategy, the candidate alloys were cast, heat treated and aged at 700 °C, and the resulting microstructure was characterized using scanning electron microscopy and atom probe tomography. The alloys with titanium addition (1 wt%) showed monotonic precipitate coarsening. On the other hand, the alloys with tungsten addition (6 wt%) showed a reduced coarsening rate of Laves phase precipitates in the matrix up to 1008 h aging, whereas an acceleration of the precipitate coarsening after that. Atom probe tomography of this alloy revealed the formation of a core-shell precipitate structure with a Nb/Si rich core and W-rich shell, while the alloy with Ti-addition did not show the core-shell structure. The detailed characterization results revealed that the core-shell structure was strongly correlated with the observed two-step coarsening mode in the tungsten containing alloy.

Impact of tungsten on the surface of aluminium-silicon alloy on microstructure, hardness and wear rate using GTA

A study was carried out to determine the effect of tungsten addition on hardness, microstructure and wear behaviour of surface modified as-cast Al - Si alloy. The heat source utilized for modifying the surface of the substrate was Gas Tungsten Arc. Tungsten were deposited on the Al - Si alloy substrate using poly vinyl alcohol as binder and the SMP were performed. By using Lyzer Instruments optical microscope and HITACHI SU6600 FE-SEM microstructural analysis was carried out. The hardness and wear rate of the modified layer were calculated by using a micro-hardness tester and a pin-on-disc wear tester machine. The presence of elemental composition in the modified layer was determined by using Energy Dispersive Atomic X-ray Spectroscopy and its confirmation through XRD analysis. It was inferred from this study that a fine grain microstructure was observed in the modified layer. The hardness and wear resistance was found to increase as a result of W addition and also due to the formation of dispersion strengthening mechanism. The coefficient of friction was found to be independent of the hardness.

Powder metallurgic fabricated plug targets for the synthesis of AlCrSiWN multicomponent coating systems

Monolithic and alloyed targets, conventionally produced by means of melt metallurgy, have been established as conventional target material designs for physical vapor depositions (PVD). However, integrating refractory metals into the sputtering material, leads to restrictions concerning the solubility and phase formation in the target compound. In this context, plug targets are commonly used to deposit multinary coatings with a desired chemical composition. However, producing plugs by means of melt metallurgy restricts the types and amounts of integrated elements.Since current PVD coating concepts aim at an extension of the functionality spectrum by element doping, new target concepts are required. The use of several monolithic targets is one method to produce coatings combining various elements within one coating. Yet depending on the target setup, this approach can result in a nanolaminar coating deposition. To circumvent this, a new production route, which ensures the integration of sintered CrSiW plugs in a monolithic aluminum target, is examined in this study. Two coating deposititons, each with an Al(CrSiW)20 and an Al(CrSiW)48 plug target, were performed by means of direct current (DC) magnetron sputtering and compared with a reference coating, which was synthesized using an AlCr20 target. The dense morphology of AlCrN was significantly changed to a more columnar structure due to slight additions of silicon and tungsten. High aluminum contents in AlCrN and AlCrSiWN, in turn, resulted in a distinct enhancement of the mechanical properties.

Effects of chromium and tungsten on sulfide stress cracking in high strength low alloy 125 ksi grade casing steel

Chromium and tungsten contents were varied to produce three different 125 ksi grade casing steels, and their sulfide stress cracking (SSC) behaviors were evaluated using double cantilever beam testing. The effects of chromium and tungsten on the SSC resistance were clarified by microstructure analysis and hydrogen permeation test. Reducing the chromium content and adding tungsten significantly increased the number of irreversible traps and decreased the proportion of the Σ3 boundaries and high-angle grain boundaries. Moreover, the addition of tungsten led to the reduction of hydrogen permeability and diffusivity, resulting in the enhancement of SSC resistance.

Electrodeposition of corrosion-resistant Cr–P and Cr–P–W coatings from solutions based on compounds of trivalent chromium

Corrosion-resistant Cr–P and Cr–P–W coatings were obtained by electrodeposition from aqueous and aqueous–organic (DMF/water) solutions. The inclusion of phosphorus in the deposits formed on the cathode was confirmed using the EDX and XPS techniques. X-ray diffraction data revealed that co-deposition of phosphorus with chromium resulted in amorphization of the obtained coatings. It was shown that the incorporation of phosphorus into the coatings leads to the disappearance of the region of potentials corresponding to active metal dissolution as compared to Cr coatings. As a result, the coatings demonstrate higher corrosion resistance. Cracking of Cr–P coatings leads to a decrease in their protective ability with respect to steel. The impossibility of obtaining thick Cr–P layers by electrodeposition from aqueous solutions limits the sphere of their possible application. This problem was solved by electrodeposition of Cr–P–W coatings from aqueous–organic media. At coating thicknesses above 10 μm, fully penetrating pores in Cr–P–W coatings practically disappeared. The addition of tungsten to the composition of cathodic deposits resulted in an additional increase in their corrosion resistance.

Transcriptome and proteome analyses of red blood cells from rainbow trout challenged with viral haemorrhagic septicaemia virus

Chromium and tungsten contents were varied to produce three different 125 ksi grade casing steels, and their sulfide stress cracking (SSC) behaviors were evaluated using double cantilever beam testing. The effects of chromium and tungsten on the SSC resistance were clarified by microstructure analysis and hydrogen permeation test. Reducing the chromium content and adding tungsten significantly increased the number of irreversible traps and decreased the proportion of the Σ3 boundaries and high-angle grain boundaries. Moreover, the addition of tungsten led to the reduction of hydrogen permeability and diffusivity, resulting in the enhancement of SSC resistance.

Effects of tungsten and rhenium additions on phase-separation in a model Ni-Al-Cr-W-Re superalloy: A four-dimensional study

The effects of a combined 1.0 at.% W and 1.0 at.% Re addition to a model Ni-10.0Al-8.5Cr at.% superalloy aged at 1073 K (800 °C) for aging times up to 256 h are investigated using atom-probe tomography (APT) and Vickers microhardness measurements. The nanoscale properties, including volume fraction, mean-volume equivalent-radius and number density of the γ′(L12)-precipitates, the chemical compositions of the γ(f.c.c.)-matrix and γ′(L12)-precipitates, the concentration profiles and partitioning ratios between the two phases, γ(f.c.c.)/γ′(L12), hetero-interfacial concentration widths, and microhardness are measured as function of increasing aging time. Localized excesses of the solvent Ni at the γ(f.c.c.)/γ′(L12) interfaces persist at aging times as long as 256 h. Transient diffusional concentration gradients associated with solute-atoms during diffusion-limited growth exist in either the γ(f.c.c.)-matrix or γ′(L12)-precipitates for the as-quenched state; these gradients disappear after 0.25 h for Al and Cr, and after 1 h for W and Re. Tungsten partitions to the γ′(L12)-precipitates and Re partitions to the γ(f.c.c.)-matrix, respectively, and this partitioning behavior enhances the partitioning of Al to the γ′(L12)-precipitates and Cr to the γ(f.c.c.)-matrix. The partitioning behavior indicates that W and Re evolve temporally more slowly than Al and Cr due to their small diffusivities in Ni. The interfacial concentration widths in the Ni-Al-Cr-W-Re alloy decrease with increasing aging time and increasing mean precipitate-radius. Adding W and Re to the base Ni-10.0Al-8.5Cr at.% alloy increases the γ′(L12)-precipitate volume fraction and the microhardness due to the increased volume-fraction and solid-solution strengthening provided by W and Re.

Microstructure and mechanical properties of reaction‐hot‐pressed zirconium diboride based ceramics

AbstractZrB2 ceramics were prepared by in‐situ reaction hot pressing of ZrH2 and B. Additions of carbon and excess boron were used to react with and remove the residual oxygen present in the starting powders. Additions of tungsten were utilized to make a ZrB2‐4 mol%W ceramic, while a change in the B/C ratio was used to produce a ZrB2‐10 vol% ZrC ceramic. All three compositions reached near full density. The baseline ZrB2 and ZrB2–ZrC composition contained a residual oxide phase and ZrC inclusions, while the W‐doped composition contained residual carbon and a phase that contained tungsten and boron. All three compositions exhibited similar values for flexure strength (~520 MPa), Vickers hardness (~15 GPa), and elastic modulus (~500 to 540 GPa). Fracture toughness was about 2.6 MPa m1/2 for the W‐doped ZrB2 compared to about 3.8 MPa m½ for the ZrB2 and ZrB2–ZrC ceramics. This decrease in fracture toughness was accompanied by an observed absence of crack deflection in the W‐doped ZrB2 compared with the other compositions. The study demonstrated that reaction‐hot‐pressing can be used to fabricate ZrB2 based ceramics containing solid solution additives or second phases with comparable mechanical properties.

Efficient CO (carbon monoxide) oxidation using gold catalysts supported on WO3/titanate protonated nanotubes

WO3/titanate protonated nanotubes used to disperse gold nanoparticles were prepared by the deposition-precipitation with urea method and tested in CO oxidation reaction. Remarkably enhanced CO oxidation activity was achieved with the addition of gold nanoparticles with respect to WO3/NT and Au/NT catalysts. XPS and H2/TPR showed that when the samples were activated at 400 °C under hydrogen treatment, gold was present in the metallic Au0 form and tungsten as W5+ and W6+ species; likewise, the addition of tungsten to the tubular morphology led to the formation of vacancies and new adsorption sites, preserving the structure at up to 400 °C. The interaction between WO3 and the titanate nanotubes was improved by adding gold nanoparticles with sizes around 1 and 3 nm under hydrogen treatment, increasing the content of reduced W5+ species that promoted the CO oxidation at low temperatures. The 2Au-3WO3/NT catalyst was active from 0 °C and showed temporary stability at room temperature.

Nickel Nanocrystal Assemblies as Efficient Electrocatalysts for Hydrogen Evolution from pH‐Neutral Aqueous Solution

AbstractEarth‐abundant elements based efficient and stable electrocatalyst for hydrogen generation from pH‐neutral aqueous solutions is highly desired, but still a momentous task. Herein, we report a nickel nanocrystal assembled nanoparticles (Ni−SP) synthesis through a simple solution phase ultrasonic‐assisted chemical reduction method. The addition of tungsten (W) metal as a non‐3d high valency element and non‐metals (B and P) as low valency element could modulate the hydrogen adsorption energy for efficient catalysis of the hydrogen evolution reaction (HER). For HER in pH‐neutral buffer solution, the Ni−SP needs 38 and 214 mV overpotential to drive 10 and 100 mA cm−2 current densities, respectively. Moreover, the catalytic activity of Ni−SP remains unaffected after 10 h of hydrogen production at 100 mA cm−2 current density, presenting superior stability and activity as compared to Pt/C.

Effects of tungsten additions on the microstructure and mechanical properties of CoCrNi medium entropy alloys

W element has a much higher atomic radius and Young's modulus than that of Co, Cr and Ni elements. In this work, the effects of W additions on recrystallized behaviors, mechanical properties and plastic deformation of CoCrNi medium entropy alloy are investigated. The results indicate recrystallized behaviors of alloys are retarded as the increase of W content. The activation energy of (CoCrNi)97W3 alloy dramatically increases (393.3 kJ/mol), indicating slow grain coarsening kinetics. For completely recrystallized alloys annealed at 900 °C with low W content (1 at. %), grain boundary hardening is the predominant reason for the yield strength increment compared with the CoCrNi alloy, but for alloys with high W content (3 at. %), the solid solution hardening and grain boundary hardening have the same contributions on the yield strength increment (∼120 MPa). The lattice friction stress and Hall-Petch slope of (CoCrNi)97W3 alloy are 291 MPa and 487 MPa μm−0.5, respectively. Overall, 3 at. % W additions improve yield strength of CoCrNi alloy by ∼33%, and maintain high ductility and work hardening ability.

Hydrothermal and sulfur aging of CeTi/CeWTi catalysts for selective catalytic reduction of NOx with NH3

The CeO2-TiO2 (CeTi) and CeO2/WO3-TiO2 (CeWTi) catalysts were prepared by sol-gel method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol% H2O to obtain the hydrothermal aged catalysts. The sulfur aged catalysts were treated at 400 °C with 100 ppm SO2, 10% water vapor, air balance for 48 h and catalysts. The powder X-ray diffraction (XRD) and Raman results indicate that the crystallization of hydrothermal aged catalysts is more serious than sulfur aged catalysts. In addition, tungsten species can stabilize the CeTi catalyst from grain growth. According to the results of in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), temperature-programmed desorption of ammonia (NH3-TPD), H2 temperature-programmed reduction (H2-TPR) and ammonia oxidation, the aging process leads to loss of surface area, redox properties, surface acidities and surface ceria concentration, especially for the hydrothermal aging. The NH3-NO/NO2 SCR performances of sulfur aged catalysts are better than that of hydrothermal aged catalysts. Compared with CeTi catalyst, the addition of tungsten inhibits the crystallization of catalyst. So that more acid sites and active sites are retained. This is also the reason why tungsten addition improves the NH3-NO/NO2 SCR performance of CeTi catalyst.

Influence of Cerium and Tungsten Addition on the Passive Behaviour of 444-type Ferritic Stainless Steels

Influence of Cerium and Tungsten Addition on the Passive Behaviour of 444-type Ferritic Stainless Steels

Selective anaerobic fermentation of syngas into either C2-C6 organic acids or ethanol and higher alcohols

Clostridium carboxidivorans produces alcohols from C1 gases (CO, CO2), converting them first into fatty acids, and subsequently into alcohols. This research identified conditions that allow to selectively produce either fatty acids or alcohols. The conversion of gases into acids and then into alcohols is catalysed by metalloenzymes, stimulated by specific trace metals. Therefore, different bioreactors were set-up, either with or without addition of tungsten (W) or selenium (Se) and at different pHs. Combining the presence of those trace metals with a low pH (5.0) allowed to accumulate high amounts of alcohols as major end products (8038 mg/L total alcohols; 3027 mg/L total acids). Instead, maintaining a higher pH (6.2), in the absence of those trace metals, allowed to selectively produce organic acids (9577 mg/L) and almost no alcohols (676 mg/L). Omitting W, but not Se, at high pH (6.2), led to a still higher concentration of acids (11303 mg/L).