Effect Of Tungsten Content Research Articles

Electrodeposition of Ni-W Alloy from Citric Acid Free Aqueous Electrolyte As a Substitute for Hard Chrome Coating and the Effect of Tungsten Content on Coating Hardness

In the industry, chrome coating is an important player in the functional layer application. Due to its high corrosion and wear resistance as well as high hardness [1], hard chrome plating is a popular choice in the automotive and aerospace industry. However, since September 2017, the application of chrome (VI) in surface treatment is banned by the European Chemical Agency (ECHA) due to chrome (VI) being toxic and environmentally hazardous [2]. Chrome (III) compound is a popular substitute for chrome (VI) due to it being less toxic compared to chrome (VI). However, chrome (III) coating has a lower corrosion resistance, and the electroplating process is more sensitive to metallic impurities.Many new innovations have since been developed such as the plasma electrolytic oxidation (PEO), extreme highspeed laser deposition (EHLA). Even established technologies such as physical vapour deposition (PVD), thermal spraying and case hardening process have tried to replace hard chrome coating with a degree of success. Admittedly, the above-mentioned technologies have their fair share of disadvantages. PEO, a green procedure [3], causes a metal substrate to develop a highly resistant oxide which is extremely strong and corrosion as well as wear resistant. The process however needs a high temperature and pressure, continuous replacement of electrolytes and consumes a great amount of power which made the process not feasible for a wide industrial application [4-6]. EHLA and thermal spraying on the other hand are restricted to rotational symmetric components. PVD is restricted to substrates that can handle high processing temperature like nitrable ferrous base materials. Lastly, case hardening processes requires long heat treatments which contribute to a higher process cost. [7]In our presentation, another alternative for chrome coating based on electrodeposition will be introduced. The element tungsten is considered in our experiments because tungsten not only has an excellent corrosion properties and high tensile strength at high temperature, but it also has a microhardness of 650 Vickers. However, it is not possible to deposit tungsten from an aqueous solution because tungstate cannot be directly reduced to metallic tungsten due to a very low overvoltage for hydrogen evolution on tungsten. Thus, an induced co-deposition mechanism is needed, and it is known that tungsten can be easily codeposited with iron group metal. [8-9]In this study a modified Watt’s bath is used as electrolyte to deposit NiW alloy. Our preliminary tests have shown that tungsten can also be deposited with nickel without the help of citric acid as complexing agent. The usage of citric acid does indeed inhibit the deposition of nickel but show no influence in the deposition of tungsten. Hence, in our study, experiments with the rotating disc electrode (RDE) will be done to see if tungsten content in the coating could be increased when the hydrodynamic and coating parameters are manipulated. The chemical composition of the layer is measured using SEM/EDX and the surface morphology is pictured using SEM. Metallographic cross-sections are made to see if there are any fissures in the layer and the hardness of the layer is measured using the microhardness test. The dependency of hardness on the tungsten content in the layer and the annealing parameter will also be shown in the presentation. XRD measurement is conducted for phase analysis and grain size calculation. Figure 1

Catalytic pyrolysis of HDPE over WOx/Al2O3: Effect of tungsten content on the acidity and catalytic performance

A series of WOx/Al2O3 catalysts with different tungsten contents were prepared by an incipient-wetness impregnation method for use in the pyrolysis of high density polyethylene (HDPE) to liquid oil. Physicochemical properties of the catalysts were investigated by N2 physisorption, field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy analyses. Acid properties of the catalysts were examined by FT-IR analyses of pyridine-adsorbed catalysts and NH3-TPD (temperature programmed desorption) experiments to elucidate the catalytic performance. The catalytic pyrolysis of HDPE was carried out over WOx/Al2O3 catalysts in a batch-type pyrex reactor at atmospheric pressure. It was found that HDPE conversion and oil yield showed volcano-shaped trends with respect to the tungsten content of the WOx/Al2O3 catalysts. Among the catalysts tested, the 6.25 wt% WOx/Al2O3 catalyst with the largest acidity showed the best catalytic performance. A correlation between the catalytic performance (HDPE conversion and oil yield) and acidity showed that the catalytic performance increased with the increasing acidity of the catalyst.

Effect of Tungsten Content and Compression on Microstructure and Texture Evolution in Liquid Phase Sintered Heavy Alloy

Effect of Tungsten Content and Compression on Microstructure and Texture Evolution in Liquid Phase Sintered Heavy Alloy

Experimental Investigations on The Effect of Tungsten Content on the Machining Behaviour of Tungsten Heavy Alloys

The present work attempts to assess the machinability of tungsten heavy alloys (WHAs) with varying tungsten content in terms of different machining characteristics such as chip thickness, material removal rate, cutting force and surface roughness under varied cutting conditions. The feed rate is found to have major influence on the machining characteristics; whereas the effect of rake angle appears to be marginal. With increase in W content both cutting force and material removal rate increase whereas surface roughness decreases. Since WHAs are difficult to machine, an additional objective of the study is to optimize machining parameters. An optimal balance of the experimental cutting parameters using Grey relational analysis has been achieved, which can be effectively employed for the machining of the alloys with close dimensional tolerances and desirable surface finish.

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.

The effect of tungsten content on the properties of L12-hardened Co–Al–W alloys

Ternary Co–Al–W alloys with W contents between 8 and 11at.% were investigated with respect to element partitioning, γ′ solvus, γ′ volume fraction, lattice mismatch and creep properties. W is enriched in the γ′ precipitates and an increasing W content stabilizes this phase. The lattice mismatch is positive up to 900°C and rafting occurs during creep with a preferred direction in accordance with this positive lattice mismatch.

Effect of tungsten content on properties of PVD sputtered Al–WX alloys

Al–Wx alloys with the W content ranging from 0·6 to 11 at-% were sputter deposited at a low temperature on AA7075 alloy substrates. The sputtered Al–W alloys exhibit a remarkably broad range of microstructures and were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). For the alloys with a W content from 0·6 to 3·5 at-%, increasing tungsten additions lead to a decrease in the grain size from a few hundred nm to 10 nm. At 11 at-%W, a lamella-like microstructure forms, accompanied by an amorphous phase. Nanoindentation tests revealed that the increasing tungsten additions lead to an increase in the hardness. A polarisation corrosion test in a near neutral 0·1M NaCl solution revealed that increasing the tungsten additions leads to an increasing passive range and, therefore, the pitting potential.

Development and Performance of the W/Sb2O3/KIO4/Lubricant Pyrotechnic Delay in the US Army Hand‐Held Signal

AbstractGassy pyrotechnic delays composed of tungsten, antimony(III) oxide, potassium periodate, and various lubricants have been developed for use in the US Army hand‐held signal. The new compositions were developed to replace the current formulation, which contains potassium perchlorate and barium chromate, chemicals that are facing increasing scrutiny due to environmental regulation. The hand‐held signal delay housing was used to demonstrate the burning rate tunability of the new compositions. The addition of 1–5 % of waxy lubricants (stearic acid or calcium stearate) was found to have a profound effect on burning rate. The effect of tungsten content and the Sb2O3/KIO4 ratio on burning rate was also probed. A wide range of inverse burning rates (2 to 15 s cm−1) were demonstrated, which encompasses the 7 to 8.5 s cm−1 range required by the hand‐held signal. The W/KIO4 reaction produces I2, which was observed by visible spectroscopy in the vapor above a sample of combustion residue.

Effect of tungsten content on microstructure and quasi-static tensile fracture characteristics of rapidly hot-extruded W–Ni–Fe alloys

Tungsten heavy alloys (WHAs) with three different compositions (90W–7Ni–3Fe, 93W–4.9Ni–2.1Fe and 95W–3.5Ni–1.5Fe, wt.%) were heavily deformed by one-pass rapid hot extrusion at 1100 °C with an extrusion speed of ~ 100 mm/s and an extrusion ratio of ~ 3.33:1. The influence of tungsten content on the microstructure and tensile fracture characteristics of the as-extruded alloys was investigated in detail. The results show that the tungsten particles in the as-extruded 95W have the largest shape factor compared to the as-extruded 90W and 93W alloys and this implies that the tungsten particles in the as-extruded 95W alloy were subjected to the heaviest plastic deformation. In addition, ultimate tensile strength (UTS) and hardness (HRC) are significantly improved after rapid hot extrusion. The as-extruded 95W alloy processes the highest strength (1455 MPa) and hardness (HRC40) but the lowest elongation (5%), followed by the as-extruded 93W (UTS1390MPa; HRC39; 7%) and 90W alloys (UTS1260MPa; HRC36; 10%). The fracture morphology shows the distinct fracture features between the as-sintered alloys and the as-extruded alloys. For the as-sintered alloys, the fracture modes are various while transgranular cleavage of tungsten particles is the main characteristic in the as-extruded alloy. Meanwhile, the fracture modes of the three as-extruded alloys vary slightly with the tungsten content. TEM bright field images indicate that many lath-like subgrains with the width of 150–500 nm are present in the three as-extruded alloys, particularly in the as-extruded 93W and 95W alloys. Furthermore, the dislocations are absent in the γ-(Ni, Fe) phase. This means that dynamic recovery–recrystallization process took place during rapid hot extrusion.

銅‐５０質量％タングステン焼結合金と無酸素銅との摩擦圧接 継手の引張強さに及ぼすタングステン含有量の影響

銅‐５０質量％タングステン焼結合金と無酸素銅との摩擦圧接 継手の引張強さに及ぼすタングステン含有量の影響