High-entropy Alloy Powders Research Articles

Investigation of HVOF sprayed novel Al1.4Co2.1Cr0.7Ni2.45Si0.2Ti0.14 HEA coating as bond coat material in TBC system

The present study aims to investigate non-stoichiometric Al1.4Co2.1Cr0.7Ni2.45Si0.2Ti0.14 high entropy alloy (HEA) as a bond coat material for the TBC (Thermal Barrier Coating) system. The mechanical activated synthesized HEA was sprayed on a Ni-based superalloy substrate by High-velocity oxy-fuel (HVOF) spraying, and 8 mol% Yttria Stabilized Zirconia (YSZ) was deposited on HEA by Air Plasma Spray (APS). X-Ray Diffraction (XRD) analysis and Scanning Electron Microscopy (SEM) were used to investigate the phases and microstructure of the as-synthesized HEA powder, Ni superalloy/HEA-bond coat, and Ni superalloy/HEA-bond coat/YSZ topcoat. The mechanical properties of the coating like microhardness, Young’s modulus and residual stress between bond coat and YSZ top coat was evaluated using the Nano-Hardness Tester (NHT). The TBC system was investigated for cyclic oxidation at 1050 ℃ for 100 cycles, and its cross-sections were analyzed for TGO (Thermally grown oxides) layer composition, thickness and interdiffusion of elements. The properties of the TBC system containing HEA as a bond coat were compared with those of the conventional TBC system comprising of MCrAlY (AMDRY 365–4) as a bond coat. It was observed that HEA containing TBC displayed exceptional high temperature properties and were comparable to MCrAlY.

Electromagnetic wave absorption performance of FeCoNiMn0.5Al0.2 high entropy alloys governed by nanocrystal evolution

High entropy alloys (HEA) are promising microwave absorbers because of their multiple attenuation mechanisms on both electrical and magnetic field. Noting that microstructure is the determining factor on microwave absorption for HEA with specific composition, annealing process is performed on the as-milled FeCoNiMn0.5Al0.2 HEA. The obtained HEA powder shows flaky shape with micron-scale length and nanoscale thickness and consists of nanocrystal-amorphous structure with the grain size of 6–30 nm. Results show that altering crystallinity, grain size, lattice constant, phase composition, particle morphology, defects, and internal stress allows to control the magnetic properties, electrical properties, high-frequency electromagnetic parameters, and microwave absorption. To further clarify the absorption mechanism, relaxation polarization, conductive loss, natural resonance, eddy-current loss in 2–18 GHz are systematically discussed associated with the nanocrystal evolution. The increased crystallinity and decreased lattice defects help to increase the real permeability, and shift the natural resonance to GHz, which are great favorable to improve the impedance matching and high-frequency resonance loss. Those changes also lead to great improvement on conductivity, which lead to higher real permittivity, conductive loss, and eddy-current loss. While the drop of internal stress and amorphous phase reduce the dipole polarization and relaxation polarization. The HEA annealed at 500 °C for 0.5 h realize a desirable absorption with a maximumreflection loss of −44.425 dB over a broad effective bandwidth of 3.825 GHz.

Microstructure Design of High-Entropy Alloys Through a Multistage Mechanical Alloying Strategy for Temperature-Stable Megahertz Electromagnetic Absorption

HighlightsNanocrystalline high-entropy alloy powders (HEAs) with the unprecedented combination of superior manufacturability, large aspect ratios, and thin intergranular amorphous layers are constructed via a multistage mechanical alloying strategy.FeCoNiCr0.4Cu0.2 HEAs for 20 h of dry milling and 5 h of wet milling (D20) exhibit excellent corrosion resistance, high Curie temperature, and temperature-stable broadband megahertz electromagnetic wave absorption.

Effect of hybrid carbonaceous reinforcement on structure, mechanical and wear properties of spark plasma sintered CrCoFeMnNi HEA/GNP+CNT composite

For the ultra-fine grained hybrid carbonaceous (graphene nano-plates (GNPs) + carbon nano-tubes (CNTs)) reinforced high entropy alloys (HEAs), there is a lack in understanding of the structure evaluations, mechanical and wear behaviors. In this work, the CrCoFeMnNi HEA and CrCoFeMnNi-X(GNP+CNT) (X = 0.2 and 0.8 wt%) composites were successfully fabricated via mechanical alloying (MA) following by spark plasma sintering (SPS). The effect of various contents of GNPs+CNTs on the phase and microstructure evaluations, the micro-hardness, shear deformation and wear behavior were investigated. The results demonstrated that the major FCC phase was obtained after 50 h milling for CrCoFeMnNi HEA powders, where a two-phase structure was obtained by incorporation of GNPs+CNTs. The Cr7C3 carbide and spinel oxide phases in the SPS processed CrCoFeMnNi-X(GNP+CNT) composites showed higher and lower intensities compared to those of the CrCoFeMnNi HEA, respectively. The considerably effect of GNPs+CNTs to hinder crystal growth was reflected via 31% lower coarsening of crystal size (CS) in the CrCoFeMnNi-0.2 wt% (GNP+CNT) composite than the CrCoFeMnNi HEA. The micro-hardness was improved with increasing the hybrid carbonaceous reinforcement concentration, where the surface roughness showed lessening trend. Ultimate shear stress (USS) of CrCoFeMnNi-0.2 wt% (GNP+CNT) composite (591 MPa) was the highest in comparison with CrCoFeMnNi HEA and CrCoFeMnNi-0.8 wt% (GNP+CNT) composite. The worn surface of the CrCoFeMnNi-0.8 wt% (GNP+CNT) composite presented small debris, some black adhesion and micro cracks where the worn track was the most prominent and oxidation wear resistance was significantly improved. The considerable reduction in the friction coefficient (FC) values about 16% and 43% and improvement in the wear resistance (WR) values by 81% and 91% were achieved with incorporation of 0.2 wt% and 0.8 wt% GNPs+CNTs, respectively. These indicated that hybrid carbonaceous reinforcement obviously developed self-lubricating ability, however, the efficiency of WR was affected by agglomeration of reinforcement phase.

Alloying behavior and characterization of (CoCrFeNiMn)90M10 (M=Al, Hf) high-entropy materials fabricated by mechanical alloying

The alloying behavior and microstructures of the (CoCrFeNiMn)90M10 (M=Al, Hf) high-entropy alloy (HEA) powders fabricated by mechanical alloying were studied. The CoCrFeNiMn)90Al10 powders have duplex solid-solution structures. In contrast, nanocrystalline HfNi3 anchoring in amorphous structures is found in the (CoCrFeNiMn)90Hf10 powders. The (CoCrFeNiMn)90Al10 powders show better ferromagnetic behaviors, mainly explained by the facilitated motion of the magnetic domain induced by the coherent interface between duplex phases. Combined with our previous work, the rules of forming solid-solution and amorphous phase in as-milled HEA powders are preliminarily proposed. It is found that, compared with the as-cast HEA reported previously, the variation range of mixing enthalpy with atomic size difference of the solid-solution formed in as-milled HEA powders is broader. Moreover, the variation ranges between mixing enthalpy and entropy with atomic size difference of the amorphous phase in HEA powder become wider than those of high-entropy bulk metallic glass.

Microstructure and Corrosion Behavior of Laser Cladding FeCoNiCrBSi Based High-Entropy Alloy Coatings

High-entropy amorphous alloys designed based on the concept of multi-principal components have the comprehensive advantages of high passivation element content and amorphous structure, and are considered as one of the promising alternative protective materials in extreme marine environments. However, based on the composition of traditional amorphous alloys, the multi-principal design significantly reduces its glass forming ability. In order to improve the glass formation ability of high-entropy amorphous alloys, this study attempts to design Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 alloy by microalloying on the basis of traditional FeCoNiCrBSi high-entropy amorphous alloy. The traditional Fe43.6Co6Ni17.4Cr9B17.5Si1.5Nb5 iron-based amorphous alloy was selected as the comparison material. Then, spherical alloy powders were prepared by gas atomization. The amorphous nanocrystalline composite coatings were deposited on the 304 stainless steel by laser cladding technology. The microstructure of the coatings was characterized by scanning electron microscopy and X-ray diffractometer. The corrosion behavior of laser cladding coatings in 3.5 wt.% NaCl solution were investigated in detail. The results show that the Fe43.6Co6Ni17.4Cr9B17.5Si1.5Nb5 powder is composed of FCC, Laves and boride phases. Whereas the Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 high-entropy amorphous alloy powder is composed of FCC and boride phases. Due to the remelting and multiple heat treatments during the preparation of the laser cladding coatings, borides were precipitated in both coatings. The microstructure of the two coatings from the bonding area with the substrate to the top layer are plane grains, dendrite, equiaxed grains and amorphous phase, respectively. Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 high-entropy amorphous alloy coating exhibits high corrosion potential, passivation film resistance and low corrosion current density in 3.5 wt.% NaCl solution. In addition, the passivation film formed on the coating has higher Cr content and lower defect concentration, showing more excellent corrosion resistance.

Fatigue Bending of V-Notched Cold-Sprayed FeCoCrNiMn Coatings

Cold-spray coatings were produced by FeCoCrNiMn high-entropy alloy powders deposited on carbon steel substrate. The coatings were realized at intermediate temperature and high pressure (at 1100 °C and 7 MPa). The coating microstructure was characterized by scanning electron microscopy and X-ray diffraction, revealing a very dense deposition and high flattening ratio of the splatted particles. This had a large influence on the strong adhesion of the coating to the substrate. The hardness and residual stress profiles were measured through nanoindentation and X-ray diffraction from the peak broadening measured layer by layer. The cyclic behavior of the coatings was evaluated through three-point bending tests performed on V-notched samples coated via cold spray. Cyclic tests were performed at different maximum strokes from 0.3 to 3.6 mm in order to monitor the crack initiation and propagation during bending tests. The fracture surface aspect was analyzed by scanning electron microscopy in order to reveal the fracture mechanisms in different deformation conditions.

Effects of milling process parameters and PCAs on the synthesis of Al0.8Co0.5Cr1.5CuFeNi high entropy alloy powder by mechanical alloying

Nine schemes were designed to study the effects of milling parameters (rotational speed, balltopowderweightratio, milling time) and process control agents (PCAs) on the synthesis of Al0.8Co0.5Cr1.5CuFeNi powders by mechanical alloying (MA). By using X-ray diffraction (XRD), the solid solutions formation during MA were studied, the grain size and lattice strain were calculated. The morphology, microstructure and composition of the powders were analyzed by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The grain size decreased as rotational speed, milling time, balltopowderweightratio increased, the change of lattice strain was opposite. The carbon and oxygen pollution levels introduced by stearic acid were higher than those introduced by n-heptane and lower than those introduced by ethanol. The powders were hardly alloyed when stearic acid was added at initial stage, but could be effectively alloyed after pre-alloying. Cold-welding was effectively inhibited and particles were greatly refined when 1 wt% ethanol and stearic acid were added respectively. Solid solutions formation was affected by cold-welding and fracture. Severe cold-welding led to Fe, Cr, Ni rich regions formation. Refinement of particles and enrichment regions resulted in the increase of concentration gradient sites, accelerating dissolution and alloying.

Sustaining strength-ductility synergy of SLM Fe50Mn30Co10Cr10 metastable high-entropy alloy by Si addition

Metastable high entropy alloys possesses excellent ductility and toughness, but its low strength hinders its engineering applications. Therefore, many studies have been carried out to improve the strength of metastable high entropy alloys while maintaining high ductility. In this paper, a new high entropy alloy is fabricated by selective laser melting (SLM) with the addition of Si powder into Fe50Mn30Co10Cr10 metastable high entropy alloy powders, with compositions (Fe50Mn30Co10Cr10)100-xSix (x = 0, 1, 3, 5). The results show that the yield strength and ultimate tensile strength of Si-containing metastable high-entropy alloys gradually increase with the increase of Si elements, and the performance is far better than that of without Si addition. The Si element increases the metastability of the γ(FCC) phase in the high-entropy alloy, and promotes the phase transformation-induced plasticity by adjusting the twinning strain during the deformation process; so that the total elongation of the material prepared by SLM can reach 30% and above. The combined effect of multiple strengthening mechanisms such as dislocation, deformation twinning, and phase transformation has greatly increased the strength of high-entropy alloys. In addition, the excellent strength-ductility combination of the alloy containing Si element indicates that the composition has good printability for laser additive manufacturing, which can provide a reference for expanding the diversification of high-entropy alloys in the additive manufacturing process.

Influence of Mo on the Microstructure and Corrosion Behavior of Laser Cladding FeCoCrNi High-Entropy Alloy Coatings.

FeCoCrNi and FeCoNiCrMo0.2 high-entropy alloy powders were prepared by gas atomization. Two kinds of coatings were prepared on the surface of 304 stainless steel by laser cladding technology. The effect of Mo element on the microstructure of laser cladding FeCoCrNi coating and its corrosion behavior in 3.5 wt.% NaCl solution was investigated. Both FeCoCrNi and FeCoCrNiMo0.2 powders exhibit a single-phase FCC structure. Due to the remelting and multiple heat treatments during the preparation of the laser cladding coating, a small amount of σ and μ phases appeared in the FeCoCrNiMo0.2 coating. The microstructures of the two coatings from the bonding area to the top layer are planar, columnar and equiaxed grains, respectively. The addition of the Mo element causes the dendrite size in the middle region of the FeCoCrNiMo0.2 coating increases significantly and exhibits obvious orientation characteristics. FeCoCrNiMo0.2 coating has high corrosion potential (−0.01 VSHE) and low current density (0.94 × 10−7 A/cm2) in 3.5 wt.% NaCl solution, showing excellent corrosion resistance. The passivation film formed on corroded the FeCoCrNiMo0.2 coating contains high content of oxides of Cr and Mo. The addition of the Mo element enhances the compactness and pitting resistance of the passivation film.

Microstructure, preparation and properties of TiC-Fe/ FeCoCrNiMn cermet with a core-rim structure

High entropy alloys (HEAs) have become an ideal material for preparing cermets because of their properties, such as high hardness, good wear resistance, and excellent heat resistance. In this paper, TiC-Fe/HEA cermet was prepared by vacuum sintering with Fe powder, HEA(FeCoCrNiMn) powder, and TiC particles. The effect of HEA content on the microstructure and properties of TiC-Fe cermet was studied, and the preparation process of cermet was optimized. The results show that the cermet grains without HEA are angular or polygonal, while the cermet grains with HEA are round and oval. With the addition of HEA, the grain size decreased at first and then increased. In addition, with increasing HEA content, the hardness, transverse rupture strength, and fracture toughness of cermet first increased and then decreased, while the relative density decreased slightly. HEA had the best properties among these HEA cermets at 10 wt%, and its hardness, transverse rupture strength (TRS), and fracture toughness (KIC) reached 1530 HV30, 980 MPa, and 10.57 MPa•m1/2 respectively. Compared with cermet without HEA, these values were increased by 36%, 20%, and 11%, respectively.

Enhanced Electromagnetic-Wave Absorbing Performances and Corrosion Resistance via Tuning Ti Contents in FeCoNiCuTix High-Entropy Alloys.

Efficient and stable electromagnetic-wave (EMW) absorption materials have attracted great attention in the field of reducing microwave pollution. Herein, FeCoNiCuTix high-entropy alloys (HEAs) as electromagnetic-wave absorbing materials were prepared by a high-energy ball-milling method. The as-milled HEA powders presented a flaky shape with a high aspect ratio. Impedance matching was efficiently optimized by severe lattice distortion, which was caused by Ti incorporation. The introduced plentiful defects in FeCoNiCuTix HEAs provided abundant polarization sites for dielectric loss. By tuning Ti contents, FeCoNiCuTi0.2 HEAs delivered excellent EMW absorption performances. The maximal reflection loss (RLmax) values reached -47.8 dB at 10.86 GHz as thin as 2.16 mm, and the widest bandwidth was 4.76 GHz (5.97-10.73 GHz). Furthermore, the introduction of Ti enhanced corrosion resistance via increasing the charge transfer resistance of a passivated film. Those characteristics of FeCoNiCuTix HEAs made these materials a practical gigahertz-range EMW absorber. Additionally, our findings provided a facile and tunable strategy for designing EMW absorbing materials, which was aimed at lightweight, highly efficient absorption, and resistance to harsh environments.

Diffusion kinetics and elemental transport in selective surface nitriding of CoCrFeNiTi0.5 high entropy powder

Ceramic coated metal powders have recently found prominence owing to their prospective application in 3D microstructured metal matrix composite synthesis. To ensure a perfect matrix-reinforcement interface in these composites, the coating process needs to be in situ. To that end, we recently developed a process for in situ nitride surface coating of CoCrFeNi high entropy alloy (HEA) powder. This approach offers various advantages over other processes including ease of controlling the surface morphology and compositional control by adjusting the nitriding parameters. In this study, we aimed to elaborate the nitride layer formation mechanism, growth kinetics, and compositional control. Mechanically alloyed CoCrFeNiTi0.5 HEA powder was used as the starting powder. The nitride layer growth on the powder was observed at different temperatures of 973, 1073 and 1173 K for 1–12 h under partial nitrogen atmosphere. The nitrogen preferentially reacted with Ti to form a continuous layer of TiN on the powder surface. Further growth was found to be diffusion-controlled by the growth rate increase with increasing nitriding temperature. Morphological investigation revealed a strong efflux of Ti through the TiN grain boundaries resulting in a scale growth at the TiN/gas interface. This growth mechanism was validated by a high TiN layer growth activation of 240 kJ.mol−1. Finally it was revealed that the Cr dissolution within the TiN layer can be achieved at higher temperature. However, to retain the integrity of the surface layer, the Cr dissolution process needs better control

FeCoNiCr0.4CuX High-Entropy Alloys with Strong Intergranular Magnetic Coupling for Stable Megahertz Electromagnetic Absorption in a Wide Temperature Spectrum.

Electromagnetic (EM) absorbers serving in the megahertz (MHz) band and a wide temperature range (from -50 to 150 °C) require high and temperature-stable permeability for outstanding EM absorption performance. Herein, FeCoNiCr0.4CuX high-entropy alloy (HEA) powders with a unique nanocrystalline structure separated by a thin amorphous layer (NTA) are designed to improve permeability and enhance intergranular coupling. Simultaneously, the long-range anisotropy is introduced via devising the preparation process and tuning the chemical composition, such that the intergranular exchange interaction is further strengthened for stable permeability and EM wave absorption in a wide temperature range. FeCoNiCr0.4Cu0.2 HEAs exhibit a near-zero permeability temperature coefficient (5.7 × 10-7 °C-1) a in wide temperature range. The maximum reflection loss (RL) of FeCoNiCr0.4Cu0.2 HEAs is higher than -7 dB with 5 mm thickness at -50-150 °C, and the absorption bandwidth (RL < -7 dB) can almost cover 400-1000 MHz. Furthermore, FeCoNiCr0.4Cu0.2 HEAs also have a high Curie temperature (770 °C) and distinguished oxidation resistance. The permeability temperature dependence of FeCoNiCr0.4CuX HEAs is investigated in-depth in light of the microstructural change induced by tuning the chemical composition, and a new inspiration is provided for the design of magnetic applications serving in wide temperature, such as transformers, sensors, and EM absorbers.

Characterizations of High Entropy Alloy Powder as Catalyst Synthesized by Mechanical Alloying for Azo Dye Degradation

FeCoNiAlSi and FeCoNiAlBSi high entropy alloys (HEAs) were synthesized by mechanical alloying. Phase evolution, crystallite size, lattice strain, microstructure and morphology for the two alloys were investigated. It was found that two simple structures which are face-centred cubic (FCC) and body-centered cubic (BCC/B2) solid solution appear in FeCoNiAlSi HEA after 50 h of milling. Formation of Fe2B peak was observed in the XRD pattern when a small amount of boron was added to the base alloys. The particle size of the alloy was increased after 20 h of milling time. The structural analysis shows that the average crystallite size decreases while lattice grain size increases with the increasing milling time. The morphology structure of the milled powders shows the particles size becomes rounded, flat and rough as the milling time prolongs. The newly developed HEA synthesized by mechanical alloying is expected to provide prominent efficiency in degradation of azo dyes (Methyl Orange). Although the HEAs have been reported to provide larger surface area and excellent capacity, only a few studies have been reported on degradation of azo dye by using HEAs as catalyst. Therefore, the method derived from the results of this study will contribute in treating azo dyes for wastewater treatment. Keywords: azo dye; high entropy alloys; mechanical alloying; crystal structure; morphology

Microstructural, Mechanical and Wear Behavior of HVOF and Cold-Sprayed High-Entropy Alloys (HEAs) Coatings

HEAs powders, unlike standard alloys which contain one or two base elements, are new alloys that contain multiple elements in the same quantity. These materials have outstanding physical and mechanical properties and for this reason, are of great interest in the material science community for their application in advanced industrial sectors. In this investigation, cold spray (CS) and high-velocity oxy fuel (HVOF) processes were used to deposit Cantor alloy (FeCoCrNiMn) coatings. Starting feedstock powders were thoroughly characterized in terms of size, shape, phase and elastic modulus. For CS process, the coating deposition efficiency and porosity could be optimized by varying gas pressure, gas temperature and stand-off distance. In the case of HVOF process, stand-off distance influenced the thickness of the coatings. Besides, on the optimized CS and HVOF coatings, corrosion tests in 3.5% NaCl solution, as well as rubber wheel, ball on disk and jet erosion tests were carried out to evaluate their wear behavior. Also, to benchmark the corrosion and wear behavior of optimized coatings, the results were compared to 316L and C-Steel bulks. The tribological study shows that Cantor alloy coatings deposited via CS and HVOF are promising to protect parts and components in a harsh environment.

High-entropy oxides as advanced anode materials for long-life lithium-ion Batteries

High-Entropy Oxides (HEOs) are a novel type of perspective anode materials for lithium ion batteries (LIBs), owing to their stable crystal structure and high theoretical capacity. However, the understanding of their intrinsic crystal structure and lithium storage mechanism is relatively shallow, hindering their further development and application. In this work, (FeCoNiCrMn)3O4 HEO was prepared successfully by the oxidation of high-entropy FeCoNiCrMn alloy powders, and was applied as a new advanced anode material for LIBs. The as-prepared (FeCoNiCrMn)3O4 HEO exhibited excellent cycle stability, and achieved a high reversible capacity of 596.5 mA h g−1 and a good capacity retention of 86.2% after 1200 cycles at 2.0 A g−1. Such long cycle stability can be ascribed to its special crystal structure and narrow band gap, which was verified by density functional theory (DFT) calculations. During the first cycle of lithium insertion, (FeCoNiCrMn)3O4 HEO gradually transformed into fine crystals below the XRD detection threshold, which was confirmed by in situ XRD. Our results demonstrate that high-entropy makes (FeCoNiCrMn)3O4 HEO possess a stable structure and narrow band gap, and three-dimensional spinel structure provides a channel for ion transport. This points out the direction for the preparation of HEOs with stable structure and excellent performance, and provides a promising candidate for anode materials of LIBs.

Microstructure and elevated temperature wear behavior of laser-cladded AlCrFeMnNi high-entropy alloy coating

The AlCrFeMnNi high-entropy alloy (HEA) coatings were deposited on 316L stainless steel through laser cladding technology that employs pre-alloyed HEA powders. The microstructure, phase composition and hardness of the laser-cladded coatings prepared at different laser scanning speeds were investigated. The wear behavior and properties of the HEA coatings at different temperatures (from room temperature to 600 °C) was comprehensively evaluated using a pin-on-disc test. It was demonstrated that the laser-cladded AlCrFeMnNi HEA coatings exhibited dense and uniform microstructures consisting of a single BCC solid solution phase. A columnar-to-equiaxed transition structure feature was observed in the molten pool of the laser-cladded coating. The coatings possessed better high-temperature wear performance due to the protective effect of oxide films on the wear track. The coating at 400 °C exhibited the best wear resistance, which had the lowest friction coefficient and wear rate of 0.48 and 1.246 × 10−4 mm3/N · m, respectively. At room temperature, the main wear mechanism of the coating was abrasive wear. However, the predominant wear mechanism at high temperatures was oxidation and adhesive wear.

Refractory WMoNbVTa high-entropy alloy as a diffusion barrier between a molybdenum substrate and MoSi2 ceramic coating

Coating a MoSi2 ceramic layer on Mo substrates is an excellent strategy to enhance their oxidation resistance at elevated temperatures. Suppressing elemental interdiffusion across the Mo/MoSi2 interface is very important for extending the service life of Mo substrates. The present study attempted to develop a WMoNbVTa high-entropy alloy (HEA) layer as a diffusion barrier at the Mo/MoSi2 interface. A new double-layer WMoNbVTa/MoSi2 coating was fabricated on Mo substrates through a two-step spark plasma sintering (SPS) method. Then, the interdiffusion behaviors of Mo/WMoNbVTa/MoSi2 and Mo/MoSi2 systems at 1200–1500 °C were investigated comparatively. A WMoNbVTa HEA powder with a single body-centered cubic (BCC) structure was prepared through mechanical alloying and the intermediate WMoNbVTa HEA layer was successfully fabricated using the milled HEA powder. After long-term oxidation, two diffusion layers of Mo5Si3 and (WMoNbVTa)5Si3 appeared at the WMoNbVTa/MoSi2 interface, while no apparent diffusion zone was found at the Mo/WMoNbVTa interface. The growth rate of the thickness of the diffusion layer at the Mo/WMoNbVTa/MoSi2 interface was much lower than that at the Mo/MoSi2 interface. The WMoNbVTa HEA layer effectively suppressed the interdiffusion of alloying elements between the Mo substrate and MoSi2 ceramic coating. This is attributed to the sluggish diffusion effect of the WMoNbVTa HEA during high-temperature oxidation. The results suggest that WMoNbVTa HEA can be a suitable diffusion barrier between Mo substrates and MoSi2 ceramic coating.

Effect of Elemental Substitution and Heating on the Phase Structure and Magnetic Properties of Mechanically Alloyed Feconialmn1-Xcrx High Entropy Alloy Powder (Heap)

Effect of Elemental Substitution and Heating on the Phase Structure and Magnetic Properties of Mechanically Alloyed Feconialmn1-Xcrx High Entropy Alloy Powder (Heap)