scholarly journals Influence of Aluminum and Molybdenum on the Microstructure and Corrosion Behavior of Thermally Sprayed High-Entropy Alloy Coatings

2021 ◽  
Author(s):  
Martin Löbel ◽  
Thomas Lindner ◽  
Maximilian Grimm ◽  
Lisa-Marie Rymer ◽  
Thomas Lampke
Keyword(s):  
Corrosion Resistance ◽  
Protective Coatings ◽  
Base Alloy ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Oxide Content ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Structural And Functional Properties ◽  
Wide Range

AbstractHigh-entropy alloys (HEAs) have shown a wide range of promising structural and functional properties. By the application of coating technology, an economical exploitation can be achieved. The high wear and corrosion resistance of HEAs make them particularly interesting for the application as protective coatings. Especially for alloys with a high chromium content, a high corrosion resistance has been revealed. For the current investigations, the equimolar HEA CrFeCoNi with a single-phase face centered cubic structure is considered as a base alloy system. To increase the corrosion resistance as well as the hardness and strength, the influence of the alloying elements aluminum and molybdenum is analyzed. For the current investigations, the high kinetic process high-velocity oxygen fuel thermal spraying (HVOF) has been considered to produce coatings with a low porosity and oxide content. Feedstock is produced by inert gas atomization. The influence of the alloy composition on the microstructure, phase formation and resulting property profile is studied in detail. A detailed analysis of the corrosion resistance and underlying mechanisms is conducted. The pitting and passivation behavior are investigated by potentiodynamic polarization measurements in NaCl and H2SO4 electrolyte. A distinct improvement of the corrosion resistance can be achieved for the alloy Al0.3CrFeCoNiMo0.2.

scholarly journals Compositional Design of Soft Magnetic High Entropy Alloys by Minimizing Magnetostriction Coefficient in (Fe0.3Co0.5Ni0.2)100−x(Al1/3Si2/3)x System

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 382 ◽  
Author(s):  
Yong Zhang ◽  
Min Zhang ◽  
Dongyue Li ◽  
Tingting Zuo ◽  
Kaixuan Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Base Alloy ◽  
Soft Magnetic Materials ◽  
Tensile Yield Strength ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
Soft Magnetic ◽  
High Entropy ◽  
Wide Range ◽  
Magnetostriction Coefficient

Developing cost-effective soft magnetic alloys with excellent mechanical properties is very important to energy-saving industries. This study investigated the magnetic and mechanical properties of a series of (Fe0.3Co0.5Ni0.2)100−x(Al1/3Si2/3)x high-entropy alloys (HEAs) (x = 0, 5, 10, 15, and 25) at room temperature. The Fe0.3Co0.5Ni0.2 base alloy composition was chosen since it has very the smallest saturation magnetostriction coefficient. It was found that the (Fe0.3Co0.5Ni0.2)95(Al1/3Si2/3)5 alloy maintains a simple face-centered cubic (FCC) solid solution structure in the states of as-cast, cold-rolled, and after annealing at 1000 °C. The alloy after annealing exhibits a tensile yield strength of 235 MPa, ultimate tensile strength of 572 MPa, an elongation of 38%, a saturation magnetization (Ms) of 1.49 T, and a coercivity of 96 A/m. The alloy not only demonstrates an optimal combination of soft magnetic and mechanical properties, it also shows advantages of easy fabrication and processing and high thermal stability over silicon steel and amorphous soft magnetic materials. Therefore, the alloy of (Fe0.3Co0.5Ni0.2)95(Al1/3Si2/3)5 holds good potential as next-generation soft magnets for wide-range industrial applications.

Effect of Ta Addition on Structural Evolution and Mechanical Properties of the CoFeNi2W0.5 High Entropy Alloy

2016 ◽  
Vol 849 ◽  
pp. 34-39 ◽  
Author(s):  
Li Jiang ◽  
Yong Dong ◽  
Hui Jiang ◽  
Yi Ping Lu ◽  
Zhi Qiang Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Vickers Hardness ◽  
Solution Structure ◽  
Structural Evolution ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Microstructure And Mechanical Properties ◽  
Electron Microscopes

A series of CoFeNi2W0.5Tax (x = 0-0.6) high entropy alloys (HEAs) were synthesized by arc melting to investigate the alloying effect of Ta element on the microstructure and mechanical properties of the CoFeNi2W0.5 alloy system. Phase constitution, microstructure and mechanical properties of the alloys were analyzed by X-ray diffraction (XRD), scanning electron microscopes (SEM), Vickers hardness and compressive test. It was found that when x = 0, the alloy consists of a single-phase face-centered cubic (FCC) solid solution structure and exhibit excellent ductility, the compressive plastic elongation of which can reach 80% without fracture. While with increasing Ta content, the brittle Co2Ta-type Laves phase appears which leads to a decrease of the plastic strain and an increase of the yield strength, and the Vickers hardness shows an obvious increase from HV 179.5 to HV 753.2.

scholarly journals Corrosion Behavior of Selectively Laser Melted CoCrFeMnNi High Entropy Alloy

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1029 ◽  
Author(s):  
Jie Ren ◽  
Chaitanya Mahajan ◽  
Liang Liu ◽  
David Follette ◽  
Wen Chen ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Laser Processing ◽  
Electrochemical Impedance ◽  
Processing Parameters ◽  
High Entropy Alloy ◽  
Elemental Distribution ◽  
Powder Bed ◽  
High Entropy ◽  
Wide Range ◽  
Superior Corrosion Resistance

CoCrFeMnNi high entropy alloys (HEAs) were additively manufactured (AM) by laser powder bed fusion and their corrosion resistance in 3.5 wt% NaCl solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests. A systematic study of AM CoCrFeMnNi HEAs’ porosity under a wide range of laser processing parameters was conducted and a processing map was constructed to identify the optimal laser processing window for CoCrFeMnNi HEAs. The near fully dense AM CoCrFeMnNi HEAs exhibit a unique non-equilibrium microstructure consisting of tortuous grain boundaries, sub-grain cellular structures, columnar dendrites, associated with some processing defects such as micro-pores. Compared with conventional as-cast counterpart, the AM CoCrFeMnNi HEAs showed higher pitting resistance (ΔE) and greater polarization resistance (Rp). The superior corrosion resistance of AM CoCrFeMnNi HEAs may be attributed to the homogeneous elemental distribution and lower density of micro-pores. Our study widens the toolbox to manufacture HEAs with exceptional corrosion resistance by additive manufacturing.

scholarly journals Microstructure and Properties of CoCrFeNi(WC) High-Entropy Alloy Coatings Prepared Using Mechanical Alloying and Hot Pressing Sintering

Coatings ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 16 ◽  
Author(s):  
Juan Xu ◽  
Shouren Wang ◽  
Caiyun Shang ◽  
Shifeng Huang ◽  
Yan Wang
Keyword(s):  
Wear Resistance ◽  
Corrosion Resistance ◽  
Mechanical Alloying ◽  
Hot Pressing ◽  
High Entropy Alloy ◽  
Solid Solution Phase ◽  
Second Phase ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Hot Pressing Sintering

The CoCrFeNi high-entropy alloy coatings (HEACs) with different weight ratios (10 and 30 wt.%) of WC additions have been prepared using mechanical alloying and a vacuum hot pressing sintering technique on a Q235 steel substrate. The microstructures, microhardness, wear resistance, and corrosion resistance of HEACs were studied. The CoCrFeNi(WC) powders were obtained by mixing the CoCrFeNi HEA powders and WC particles. The sintered products of both HEACs with high relative density contained one solid solution phase with face-centered cubic structure, WC, and unknown precipitate phases. The transition boundary had a good metallurgical bonding with the coating and substrate. The average microhardness values of CoCrFeNi HEACs with 10 and 30 wt.% WC additions reached 475 and 531 HV respectively, which were far higher than that of the substrate (160 HV). Moreover, both coatings exhibited better wear resistance than the substrate under the same wear conditions. The 30 wt.% WC HEAC displayed the lower friction coefficient, and the shallower wear groove depth. The grain refinement strengthening and second-phase particle strengthening could be beneficial to the enhanced hardness and wear resistance of coatings with WC additions. The corrosion behavior of the tested samples in the 3.5 wt.% NaCl solution were investigated using electrochemical polarization measurements. The CoCrFeNi(WC) coatings all revealed the improved corrosion resistance. Especially, a 10 wt.% WC addition remarkably enhanced the comprehensive corrosion resistance and easy passivation of CoCrFeNi HEAC.

scholarly journals Effect of Zr Addition on the Microstructure and Mechanical Properties of CoCrFeNiMn High-Entropy Alloy Synthesized by Spark Plasma Sintering

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 810 ◽  
Author(s):  
Hongling Zhang ◽  
Lei Zhang ◽  
Xinyu Liu ◽  
Qiang Chen ◽  
Yi Xu
Keyword(s):  
Spark Plasma Sintering ◽  
Raw Materials ◽  
Alloy System ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Σ Phase ◽  
High Entropy ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Fcc Phase

As a classic high-entropy alloy system, CoCrFeNiMn is widely investigated. In the present work, we used ZrH2 powders and atomized CoCrFeNiMn powders as raw materials to prepare CoCrFeNiMnZrx (x = 0, 0.2, 0.5, 0.8, 1.0) alloys by mechanical alloying (MA), followed by spark plasma sintering (SPS). During the MA process, a small amount of Zr (x ≤ 0.5) can be completely dissolved into CoCrFeNiMn matrix, when the Zr content is above 0.5, the ZrH2 is excessive. After SPS, CoCrFeNiMn alloy is still as single face-centered cubic (FCC) solid solution, and CoCrFeNiMnZrx (x ≥ 0.2) alloys have two distinct microstructural domains, one is a single FCC phase without Zr, the other is a Zr-rich microstructure composed of FCC phase, B2 phase, Zr2Ni7, and σ phase. The multi-phase microstructures can be attributed to the large lattice strain and negative enthalpy of mixing, caused by the addition of Zr. It is worth noting that two types of nanoprecipitates (body-centered cubic (BCC) phase and Zr2Ni7) are precipitated in the Zr-rich region. These can significantly increase the yield strength of the alloys.

scholarly journals Effect of Ti Content on the Microstructure and Corrosion Resistance of CoCrFeNiTix High Entropy Alloys Prepared by Laser Cladding

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2209 ◽  
Author(s):  
Xinyang Wang ◽  
Qian Liu ◽  
Yanbin Huang ◽  
Lu Xie ◽  
Quan Xu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Laser Cladding ◽  
First Principles ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
First Principles Calculations ◽  
High Entropy ◽  
Niti Phase ◽  
Fcc Phase ◽  
Ti Content

In this paper, CoCrFeNiTix high entropy alloy (HEA) coatings were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, and corrosion resistance of the coatings were studied. The mechanism of their corrosion resistance was elucidated experimentally and by first-principles calculations. The results show that CoCrFeNiTi0.1 adopts a face-centered cubic (FCC) phase, CoCrFeNiTi0.3 exhibits an FCC phase and a tetragonal FeCr phase, and CoCrFeNiTi0.5 adopts an FCC phase, a tetragonal FeCr phase, and a rhombohedral NiTi phase. The FCC phase, tetragonal FeCr phase, rhombohedral NiTi phase, and hexagonal CoTi phase are all observed in the CoCrFeNiTi0.7 HEA. The alloys assume the dendritic structure that is typical of HEAs. Ni and Ti are enriched in the interdendritic regions, whereas Cr and Fe are enriched in the dendrites. With increasing Ti content, the hardness of the cladding layers also increases due to the combined effects of lattice distortion and dispersion strengthening. When exposed to a 3.5 wt.% NaCl solution, pitting corrosion is the main form of corrosion on the CoCrFeNiTix HEA surfaces. The corrosion current densities of CoCrFeNiTix HEAs are much lower than those of other HEAs. As the Ti content increases, the corrosion resistance is improved. Through X-ray photoelectron spectroscopy (XPS) and first-principles calculations, the origin of the higher corrosion resistance of the coatings is connected to the presence of a dense passivation film. In summary, the corrosion resistance and mechanical properties of CoCrFeNiTi0.5 alloy are much better than the other three groups, which promotes the development of HEA systems with high value for industrial application.

Study on Corrosion Resistance of High-Entropy Alloys NiCoCrFeMnCuC in Medium Acid Liquid

2011 ◽  
Vol 117-119 ◽  
pp. 1816-1819 ◽  
Author(s):  
Ze Liu ◽  
Jian Min Zeng ◽  
Hai Hong Zhan
Keyword(s):  
Crystal Structure ◽  
Corrosion Resistance ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
Arc Furnace ◽  
Cubic Crystal ◽  
High Entropy ◽  
Excellent Corrosion Resistance ◽  
Face Centered ◽  
Loss Experiment

High-entropy alloy of NiCoCrFeMnCuC were made by vacuum non-consumable arc furnace in the present work. The crystal structure of NiCoCrFeMnCuC was analyzed by XRD. The corrosion resistance of NiCoCrFeMnCuC in 10%HNO3-3%HF, 10%H2SO4, 5%HCl and 10%HF was investigated, respectively with weight loss experiment. The results show that main intermetallics of the alloy are CoCx, FeNi3 and Fe3Mn7. The NiCoCrFeMnCuC has simple crystal structures with face-centered cubic crystal structure FCC and Quartet and has excellent corrosion resistance in some medium acid liquids.

scholarly journals Nanoporous Quasi-High-Entropy Alloy Microspheres

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 345 ◽  
Author(s):  
Lianzan Yang ◽  
Yongyan Li ◽  
Zhifeng Wang ◽  
Weimin Zhao ◽  
Chunling Qin
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Specific Surface Area ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Hierarchical Porous

High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital to develop new routes to fabricate HEAs with novel three-dimensional structures and a high specific surface area. Herein, we develop a facile approach to fabricate nanoporous noble metal quasi-HEA microspheres by melt-spinning and dealloying. The as-obtained nanoporous Cu30Au23Pt22Pd25 quasi-HEA microspheres present a hierarchical porous structure with a high specific surface area of 69.5 m2/g and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern, which is different from the traditional single-phase or two-phase solid solution HEAs. To differentiate, these are named quasi-HEAs. The synthetic strategy proposed in this paper opens the door for the synthesis of porous quasi-HEAs related materials, and is expected to promote further applications of quasi-HEAs in various chemical fields.

scholarly journals Erosion and Corrosion Resistance Performance of Laser Metal Deposited High-Entropy Alloy Coatings at Hellisheidi Geothermal Site

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3071
Author(s):  
Andri Isak Thorhallsson ◽  
Francesco Fanicchia ◽  
Emily Davison ◽  
Shiladitya Paul ◽  
Svava Davidsdottir ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Microstructural Characterization ◽  
Corrosion Damage ◽  
Process Equipment ◽  
High Entropy Alloy ◽  
Low Alloy Steels ◽  
Manufacturing Defects ◽  
High Entropy ◽  
Alloy Steels ◽  
Resistance Performance

Geothermal process equipment and accessories are usually manufactured from low-alloy steels which offer affordability but increase the susceptibility of the materials to corrosion. Applying erosion-corrosion-resistant coatings to these components could represent an economical solution to the problem. In this work, testing of two newly developed laser metal deposited high-entropy alloy (LMD-HEA) coatings—CoCrFeNiMo0.85 and Al0.5CoCrFeNi, applied to carbon and stainless steels—was carried out at the Hellisheidi geothermal power plant. Tests in three different geothermal environments were performed at the Hellisheidi site: wellhead test at 194 °C and 14 bar, erosion test at 198 °C and 15 bar, and aerated test at 90 °C and 1 bar. Post-test microstructural characterization was performed via Scanning Eletron Microscope (SEM), Back-Scattered Electrons analysis (BSE), Energy Dispersive X-ray Spectroscopy (EDS), optical microscopy, and optical profilometry while erosion assessment was carried out using an image and chemical analysis. Both the CoCrFeNiMo0.85 and Al0.5CoCrFeNi coatings showed manufacturing defects (cracks) and were prone to corrosion damage. Results show that damage in the CoCrFeNiMo0.85-coated carbon steel can be induced by manufacturing defects in the coating. This was further confirmed by the excellent corrosion resistance performance of the CoCrFeNiMo0.85 coating deposited onto stainless steel, where no manufacturing cracks were observed.

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