Tungsten Steel Research Articles

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Ro-vibrationally excited molecules of deuterium are involved in non-equilibrium chemical reactions in divertor region of tokamak (see molecular assisted recombination) or in neutral beam injector to produce negative ion (see dissociative electron attachment) for fusion plasmas. These molecules produced both in a plasma volume and on surfaces are no longer in their electronic ground state X1∑g+(v”⩾0,J”) and populate non-uniformly different vibrational (v″) and rotational levels (J″). The high resolution VUV Fourier Transform spectrometer of the DESIRS beam line (SOLEIL synchrotron) is applied to directly scrutinize the ro-vibrationally excited levels of the D2 ground state from v″ = 0 to 10 and J″ up to 8 in an electron cyclotron resonance (ECR) cold plasma. This is performed for different plasma-facing materials, i.e. quartz, tantalum, tungsten, and stainless steel, in order to compare their relative impact in molecular excitation through recombinative desorption from surfaces. A significant effect of these materials on the absolute distribution of the vibrationally states has been found above v″ > 3. The experimental detection limit for Quartz is v″ = 7 whereas tungsten and stainlees steel excite the molecules up to v″ = 9 and tantalum up to v″ = 10. The use of a bare, temperature-controlled surface of Quartz as a reference, compared to metallic surfaces, allows us to determine the relative production of these excited levels. The recombinative desorption rate on tungsten and stainless steel compared to quartz is ~ 2.6 higher and reaches ~ 5 for tantalum.

Heat dissipation of electronic components by ionic wind from multi-needle electrodes discharge: Experimental and multi-physical analysis

High temperature during electronic components operation can cause the failure of PN junctions of chips, and it can even damage the entire component. Ionic wind is a promising technique for heat dissipation due to its noiseless, compact structure and flexible design. In this study, needle-ring-type ionic wind devices with multi-needle electrodes connected in parallel are developed for cooling an electronic component. The effects of the number of needles, needle electrode material (tungsten and stainless steel), inter-electrode distance on the device output velocity and cooling performance are experimentally studied for a cylindrical heat sink mounted with a heating film. A full three-dimensional multi-physical numerical method, in which the coupled effects of the electric field, air flow, and heat transfer are considered, is also established. Mutual interference of the electric fields is identified between needle electrodes. The ionic wind velocity is determined by electric field strength and the angle between the ring axis and the line that connects the needle tip and the upper edge of the ring. The wind velocity first decreases and then increases with continuously increasing inter-electrode distance. Although the electrode material has an obvious effect on the ionic wind velocity of the free flow state, the heating film surface temperature is not sensitive to the needle material, whereas it is sensitive to the inter-electrode distance and the number of needles. The output wind velocity of the four-needle layout is larger than that of the three-needle layout despite backflow inside the ring. The heating film surface temperature is below 55 °C for the two designed electrode layouts, which is lower than the safety temperature of 70 °C. This study can serve as a guideline for developing multi-electrode ionic wind cooling systems.

Sticking Probability of Ammonia Molecules on Tungsten and 316L Stainless Steel Surfaces

We present measurements of the sticking probability of ammonia on two metals, tungsten and 316L stainless steel, covered with natural surface impurities as they will be used for the international n...

A new way to net-shaped synthesis tungsten steel by selective laser melting and hot isostatic pressing

In this work, a novel tungsten steel was in-situ prepared using selective laser melting (SLM) and hot isotropic pressing (HIPing). The sample is firstly prepared by SLM from powder mixture of maraging steel and WC for the net-shaped manufacturing requirement. Then, the effects of HIPing on microstructure evolution and mechanical properties of SLMed WC/maraging steel composite were investigated with focus on in-situ reaction. The as-SLMed sample presents a composite structure of γ (Fe, Ni) (austenite) and WC, which transits into α-Fe (ferrite and martensite) matrix with a large amount of Fe(Ni)–W–C η phase precipitates after HIPing. The η phase, which shows two morphologies (sub-micro and nano scales), locates mainly in grain boundary and inner-grain of α-Fe, respectively. The interfaces between η, WC and α-Fe were determined using transition electron microscopy from barely existing partial melted WC. A stable graded multi-scaled structure appears between partial melted WC and matrix. After the HIPing process, the ultimate tensile strength and yield strength increase from 980 MPa to 561 MPa–1470 MPa and 1025 MPa, respectively, with a slight decrement in elongation from 7% to 6%.

Research and Development of the First Generation of Multifunctional Home Fitness Recliner

The first generation of multifunctional home fitness recliners is a kind of home-use portable fitness equipment that coexists with multiple functions and can be easily adjusted for strength. The fitness equipment adopts the bionic “fish-shaped” design, and uses the principle of morphological bionics to achieve the simplicity required by design and meet today’s aesthetics. While improving the aesthetics of the design equipment, it also meets the requirements of ergonomics, thereby improving the user’s sports experience. The device uses polyformaldehyde plastic, ABS plastic, shell ABS plastic (natural plastic in the groove), polyamide fiber, PVC artificial leather, plywood, sponge, rubber sponge and other plastic materials that meet national standards. 35 # steel, cold rolled steel rectangular tube, spring steel, tungsten steel and other materials that meet various technical indicators. Under the premise of safe use of equipment, multiple exercise uses can be realized.

Fusion target station on MYRRHA facility: Baseline concept

The Belgian Nuclear Research Centre SCK CEN launched the 1st phase implementation of the MYRRHA reactor. This will deploy the construction of 100 MeV proton accelerator and complimentary research facilities including a dedicated station for irradiation of fusion materials (Fusion Target Station - FTS). This paper presents a baseline pre-conceptual design and analysis of the irradiation conditions for the most common in-vessel fusion materials i.e. tungsten and Eurofer97 steel. FTS will allow a direct irradiation by protons and/or irradiation via spallation neutron source. The former concept requires application of small specimen test techniques (SSTT), while the latter enable large irradiation volume with a limit damage rates.

Deuterium retention in tungsten and reduced activation steels after 3 MeV proton irradiation

Abstract Nuclear fusion plasma-facing materials (PFM) will suffer from irradiation, leading to significant changes in the material properties. This study investigates the impact of displacement damage on the deuterium retention near room temperature. ITER grade tungsten, Eurofer-97, and HiperFer 17Cr5 steel samples are irradiated with a tandem accelerator with ~3 MeV protons at currents of 100–600 nA on 250–550 µm spots at 320±10 K. In total 33 spots from 0 to 0.9 displacements per atom (DPA) at 0–4 µm depth are irradiated on 5 samples. After irradiation, the samples are exposed to D2 plasmas with a peak ion-flux of 2.1 × 1021 D/m²s for 4 h at The long-term D retention in both W and steel increases with DPA with a saturation starting around 0.2 DPA. Retention in W increased by a factor 12 with up to 3.2 at.% D, while in steel increases up to 180 times with up to 0.08 at.% D were observed. The results highlight the importance of using steels also in PFMs. Compatibility of the results with heavy ion irradiations boosts the confidence in inter-comparability between different ion types, but also between ions and neutrons.

Microstructure evolution and mechanical properties of W/MA956 joints by brazing

Brazing experiments between tungsten and MA956 ODS steel were conducted at [Formula: see text] with different holding time to investigate the interface microstructure evolution and mechanical properties of the brazed joints. The interface microstructures were analyzed by the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), and the mechanical properties of the joints were measured to find the optimal brazing parameter. The results show that tungsten and MA956 steel has been successfully joined by brazing. The intermetallic compound of Ni–W formed at the W/BNi-2 interface, which was detrimental to the strength of the joint. Due to the excellent mutual solubility between Fe and Ni, no new formed intermetallic compound was found at MA956-brazing filler interface. The shear strength of the brazed joints with BNi-2 filler reached 246 MPa at the optimal brazing parameter [Formula: see text].

Plasma–metal junction

In this work, the concept of plasma–metal junction (pm-junction) is presented, in addition to well established physics of pn-junction, metal–semiconductor junction, semiconductor–insulator junction, etc. We demonstrate experimentally the dependence of I-V characteristics on work function of the metal for a pm-junction. The experiment is done using tungsten (W) and stainless steel (SS) having different work functions (Φm) of 4.55 eV and 4.30 eV, respectively. The W and SS planar metal probes of identical geometry were exposed to plasma simultaneously, making two distinct pm-junctions. The plasma exposed is identical for both the metals, and therefore, the difference observed in the I-V characteristics of these two pm-junctions is attributed only to the difference in an energy-band diagram of these junctions, owing to respective work function. The proposed concept of the pm-junction may simplify the complex plasma–material interactions in all laboratory plasmas, including cold glow discharges to hot fusion plasmas.

Experimental study on CNC engraving parameters of Afghan white jade

The CNC machining of nephrite is increasingly used in the jade engraving industry. As the most important standard for quality evaluation, surface roughness is influenced by cutting parameters. In this paper, taking the Buddha head as the machining object, the influence of cutting parameters on the surface quality of was studied by SYIL S7 CNC milling machine. The grooving experiment was carried out at spindle speed of 24,000 rpm, then the CAXA manufacturing engineer and JDpiant software were comparatively applied in machining. Furtherly, the influence of the spindle speed on the roughness was investigated. The research results were summarized as follows: (1) No edge breakage appeared when feed speed lower than 300 mm/min with the maximum depth of cut of 0.1 mm. In this case, when the jade is machined with the spindle speed range of 16,000–24,000 rpm, the mean roughness Ra was in the range of 1,496.111–891.842 nm. (2) JDpiant software is more suitable for CNC jade engraving than CAXA manufacturing engineer. (3) In roughing stage, only the high-speed grinding contdition is satisfied, the integrity of side profile could be guaranteed. The higher spindle speed was conducive to achieve the fine surface quality. (4) The tungsten steel cutter in finish machining stage shows better grinding ability than diamond cutter used in rough machining stage. In order to formulate an economic spindle speed, the finishing surface roughness should be considered in conjunction with the requirement of polishing.

Plasma-activated catalytic formation of ammonia from N2–H2: influence of temperature and noble gas addition

In the ITER tokamak, injection of nitrogen is foreseen to decrease the heat loads on the divertor surfaces. However, once dissociated, nitrogen atoms react with hydrogen isotopes to form ammonia isotopologues. The formation of tritiated ammonia may pose some issues with regards to tritium inventory and operation duty cycle. In this paper, we report a study of the effect of three parameters of relevance for the fusion environment on the ammonia production, including the presence of a catalytic surface, sample temperature and noble gas addition. Results of ammonia formation from N2/H2 RF plasma (both with and without tungsten or stainless steel surface) show the importance of the presence of a catalyst in the ammonia formation process. By increasing the temperature of the W samples up to 1270 K, ammonia formation demonstrated a continuous decrease due to two major factors. For high temperatures above 650 K and 830 K, for stainless steel and W, respectively, the reduction results from the thermal decomposition of ammonia. For the lower temperature range, the temperature rise leads to the formation of more stable nitrides that do not tend to react further with hydrogen to form NH2 and NH3. Interestingly, the addition of helium or argon to the N2/H2 plasma show opposite effects on the ammonia production. He effectively decreases the percentage of NH3 by acting as a barrier for the surface processes. On the other hand, argon impacts the plasma processes more, probably by increasing the active nitrogen species in the plasma and as a consequence the percentage of formed ammonia.

Electrochemical corrosion assisted laser drilling of micro-hole without recast layer

High-power pulsed laser is an efficient tool for drilling micro-holes on metal, but due to the melt ejection dominated material removal mechanism, recast layer can hardly be avoided. This paper proposes to use electrochemical corrosion as a kind of postprocessing technique to remove the laser induced recast layer. A tungsten steel wire-electrode based electrochemical machining head was designed. During the research, it was discovered that the laser and electrochemical corrosion (ECC) processes may interact due to the assist gas used in the laser drilling process. Although ECC can theoretically dissolve all kinds of metal as ions, the laser induced recast layer showed special characteristics. By comparative study, it was found that oxidative assist gas would lead to oxidizing thermal reaction on the surface of the molten metal during laser drilling, resulting in an insulating layer of oxide, which disabled the ECC to fulfil its validity on recast layer dissolving. When non-oxidative assist gas was used, the recast layer on the hole wall could easily be removed, and ideal micro hole can be produced, with smooth side wall, rounded entrance and decreased taper. After optimization of the overall drilling efficiency, the efficiency of the presented method is over 4 times higher in contrast to the conventional electrochemical drilling.

Neutron reflector analysis for the beam-port of the Missouri S&T Reactor

A preliminary neutron reflector material selection and feasibility study of an inexpensive reflector replacement for the neutron beam-port at the 200 kW Missouri University of Science and Technology Research Reactor (MSTR) was conducted using Monte-Carlo techniques. The Monte-Carlo N-Particle transport code (MCNP6.1) was used to model the neutron beam-port of the Missouri S&T Reactor in order to study the effects of adding different reflector materials, in terms of the neutron flux reaching the radiography/tomography facility in front of MSTR’s neutron beam-port. Aluminum, beryllium, titanium, nickel, nickel-58, lead, bismuth, tungsten and stainless steel reflectors were modeled to find the best neutron reflector for the beam-port. After examining reflector materials, it was concluded that none of them were an improvement over the current design. Experimental thermal flux was measured to be 1.0 × 107 ± 3.16 × 103 cm−2 s−1 at the exit of beam port for current version of beam-port. The current ratio of beam port inlet and outlet obtained from simulations was found to be 3.37 × 104. The flux of beam port inlet was determined on the order of 1.0 × 1011 cm−2 s−1 which is consistent with previous findings.

Analysis of Criteria for Assessing Safety Distance for Focused Warhead Fragments Based on CDEM

This study uses the continuum-based discrete element method (CDEM) to build a new model for warhead safety distance, simulating the fragment fields over space and time for tungsten alloy and steel fragment focused warheads to derive respective safety distances for personnel. Regarding the effects of different warhead attitudes and fragment effectiveness definitions, it is found that, for single-shot focused warheads, the fragmentation risk is significantly higher for horizontal placement than for vertical placement; the fragment safety distance inneed increases nonlinearly as the threshold energy decreases. Meanwhile, the safety distance is less affected by the threshold energy for high-density-casing charges than for low density.

Microstructure and mechanical properties of diffusion bonded W/MA956 steel joints with a titanium interlayer by SPS

Diffusion bonding is an effective technique for joining dissimilar metals. In this paper, tungsten and MA956 steel were diffusion-bonded by Spark Plasma Sintering (SPS) technique with titanium (Ti) foil as an interlayer. The bonded joints were evaluated by metallographic analysis and mechanical tests, and the results reveal that all W/Ti/MA956 joints were well bonded by efficient SPS technique. Microstructure analysis showed that W-Ti solid solution formed at W/Ti interface; reaction phases at Ti/MA956 steel interface varied with the joining temperature, e.g. intermetallics phases FeTi for 850 °C, FeTi, Fe2Ti and Cr2Ti for 900 °C and 950 °C joining temperature. The peak value of microhardness occurred at the interfaces of Ti/MA956 steel owing to the formation of intermetallic compound. All specimens of shear testing fractured at the Ti/MA956 steel interface close to MA956, and the average shear strength of joints was 182 MPa, 228 MPa and 164 MPa bonded at 850 °C, 900 °C and 950 °C respectively.

Development of tungsten armored high heat flux plasma facing components for ITER like divertor application

The dome and reflector plate are the parts of divertor plasma facing components (PFCs) of ITER tokamak which are mainly aimed for the removal of heat load of maximum 5 MW/m2 in steady state condition. The dome is a curved tungsten armoured component and the reflector plate is a straight component. These components have multi-layered joints made of various materials such as tungsten (W), OFHC copper (Cu), copper alloy (CuCrZr) and stainless steel (SS316LN). Joining of such multi-layered joints is known to be problematic due to joining of several dissimilar materials. In this paper, we report the indigenous development of medium size dome and reflector plate via vacuum brazing route for ITER like tokamak application. In order to evaluate the performance of the dome against ITER-like scenarios (maximum heat flux removal of 5MW/m2), the dome has been successfully tested for 1000 number of steady-state thermal cycles at incident heat fluxes of 3.87 MW/m2 in the High Heat Flux Test Facility (HHFTF) at IPR. Subsequent testing of additional 200 thermal cycles was also done at incident heat flux of 6 MW/m2. During the High heat flux (HHF) tests, surface temperature of W tiles reached 640oC and the beam power was restricted at 6MW/m2 to limit the temperature below 450oC at the CuCrZr heat sink. Total 1200 steady-state thermal cycles have been completed. At 6 MW/m2, the absorbed heat flux was 4 MW/m2. Engineering analysis on the HHFT of the dome has been performed using Finite element method (FEM) and Computational Fluid Dynamics (CFD) to simulate and to correlate with the experimental data. Ultrasonic immersion technique – Non destructive testing (NDT) was used to inspect the brazed joint quality of the dome before and after the HHFT. The results of the experimental details, engineering analysis and methodology adopted to fabricate the medium size dome and reflector plate are presented here.

Effect of Cu Interlayer on the Microstructure and Strength for Brazing of Tungsten/316L Steel

Brazing is an effective technique for joining tungsten and steel. However, the high residual stresses are produced due to the different coefficients of thermal expansions between tungsten and steel. Compared with the direct brazing with BNi-2 foil filler, BNi-2/Cu/ BNi-2 multiple interlayer was used as filler to minimize the residual stresses between tungsten and 316L steel. The brazing experiments were conducted at 1050 °C for 25 min using Cu foils with different thickness. The results show that tungsten and 316L steel have been successfully joined by brazing. The intermetallic compound of NiW formed at the W/BNi-2 interface, which was detrimental to the strength of the joint. The microhardness of different diffusion zones is higher than that of the substrates owing to the formation of intermetallic compound and solid solution. All specimens of shear testing fractured at the W/BNi-2 interface close to W substrate, and the average strength of joints was 197, 275 and 268 MPa with multiple interlayer thickness of 0.2 , 0.1 and 0.05 mm copper foil, respectively, while the average strength of joints was 143 MPa with BNi-2 foil filler. The significant increase in the joint shear strength can be ascribed to the Cu foil in the multiple interlayer because of with excellent plasticity and toughness.

Investigating the effect of sintering temperature on the microstructure and hardness of cemented tungsten carbide/steel bilayer

In this article, the effect of sintering temperature was studied on the microstructure and hardness of cemented tungsten carbide and steel bilayer fabricated via the powder metallurgy route. Cemented tungsten carbide was reinforced with Fe and also used as the base material for the other layer to ensure compatibility between layers. Carbon addition was varied in the steel part composition to avoid carbon-deficient bilayer samples. Optical images revealed cracks at the interface which opened up more in bilayer samples sintered at 1295°C due to high mismatch in strain rate and excessive diffusion rate. Increase in sintering temperature turned grain particles coarser and lead to a decline in hardness values while increase in carbon addition enhanced densification and progressively increased hardness. Hardness values measured far away from the interface were observed higher than those close to the interface due to the formation of weak bond at the interface.

Study of plasma induced nanostructure formation and surface morphology changes on tungsten and stainless steel at atmospheric pressure

The formation of nanostructures such as “fuzz,” holes, and flakes was observed on tungsten and stainless steel anodes in a 1 atm glow discharge with helium as the feed gas. The structures exhibited morphology similar to the tungsten fuzz growth observed in experiments that simulate wall conditions in fusion reactors, suggesting that similar physics may be present in both scenarios. The anode surface temperature ranged between 1000 and 1300 K with an ion fluence rate of order 1024 s−1 m−2. In this work, scanning electron microscope and transmission electron microscope were used to characterize the evolution of nanostructure formation as a function of time. Observed nanostructures were found to vary with the morphology of the discharge plasma attachment. The composition of the structures was found to be predominantly the native metal by using energy dispersive x-ray spectroscopy. This work gives some insight into the formation of nanostructures at atmospheric pressure, which not only has applications for material processing, but also provides potentially another avenue to study fuzz formation processes relevant to fusion plasma-wall interactions.

ECART analysis of the STARDUST dust resuspension tests with an obstacle presence

To validate dust resuspension models in fusion like conditions, different experimental campaigns in the STARDUST facility were performed at ENEA laboratories Frascati (I). In the first campaign, resuspension of Tungsten (W), Carbon (C) and Stainless Steel (SS) dusts was investigated in an “empty tank” configuration, while resuspension of the same dust types in presence of an internal obstacle was studied in the second campaign. In this work, focalized on the ECART code validation, the assessment of the code “force balance” resuspension model against the data obtained during the second campaign is performed. ECART was able to provide a good qualitative and quantitative description of the resuspension phenomena so a further step in its validation has been achieved. Further improvements for the ECART resuspension model have been also highlighted, as the necessity to treat “particle clusters” and their aggregate movements.