High entropic coatings FeCrNiTiZrAl and their properties

In our proposed empirical model, the anisotropy of the surface energy and the thickness of the surface layer of the high-entropy FeCrNiTiZrAl alloy are calculated. The thickness of the surface layer of this alloy is about 2 nm, which is an order of magnitude greater than the thickness of the surface layer of complex crystals, but is of the same order of magnitude as that of metallic glasses. The hardness and other properties of the high-entropy alloy are the same as for metallic glasses, but are 2-3 times higher than the hardness of stainless steels. The surface energy of the high-entropy FeCrNiTiZrAl alloy is about 2 J/m2, which corresponds to the surface energy of magnesium oxide and other crystals with a high melting point. However, unlike these crystals, the friction coefficients of a high-entropy alloy (~ 0.06) are much lower than that of ordinary steels (~ 0.8). We have theoretically shown that the friction coefficient is proportionally dependent on the surface energy and inversely proportional to the Gibbs energy, which significantly decreases for a high-entropy alloy, leading to low friction. The high hardness and low coefficient of friction of the high-entropy alloy facilitates the deposition of coatings from them on structural metal products, which contributes to their widespread use.

Download Full-text

Laser Assisted High Entropy Alloy Coating on Low Carbon Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.813.159 ◽

2019 ◽

Vol 813 ◽

pp. 159-164

Author(s):

Carlos Alberto Souto ◽

Gustavo Faria Melo da Silva ◽

Laura Angelica Ardila Rodriguez ◽

Aline C. de Oliveira ◽

Kátia Regina Cardoso

Keyword(s):

Wear Resistance ◽

Carbon Steel ◽

Low Carbon Steel ◽

High Hardness ◽

Alloy Coating ◽

High Entropy Alloy ◽

Nominal Composition ◽

Low Carbon ◽

High Entropy ◽

Scan Speed

Coatings with high entropy alloys of the AlCoCrFeNiV system were obtained by selective laser melting on low carbon steel substrates. The effect of the variation of the Fe and V contents as well as the laser processing parameters in the development of the coating were evaluated. The coatings were obtained from the simple powder mixtures of the high purity elemental components in a planetary ball mill. The coatings were obtained by using CO2 laser with a power of 100 W, diameter of 0.16 mm, and scan speed varying from 3 to 12 mm/s. Phase constituents, microstructure and hardness were investigated by XRD, SEM, and microhardness tester, respectively. Wear resistance measurements were carried out by the micro-abrasion method using ball-cratering tests. The coatings presented good adhesion to the substrate and high hardness, of the order of 480 to 650 HV. Most homogeneous coating with nominal composition was obtained by using the higher scan speed, 12 mm/s. Vanadium addition increased hardness and gave rise to a high entropy alloy coating composed by BCC solid solutions. Ball cratering tests conducted on HEA layer showing improvement of material wear resistance, when compared to base substrate, decreasing up to 88% its wear rate, from 1.91x10-6 mm3/Nmm to 0.23x10-6 mm3/Nmm.

Download Full-text

Enhanced Wear Behaviour of Spark Plasma Sintered AlCoCrFeNiTi High-Entropy Alloy Composites

Materials ◽

10.3390/ma11112225 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2225 ◽

Cited By ~ 9

Author(s):

Martin Löbel ◽

Thomas Lindner ◽

Thomas Lampke

Keyword(s):

Wear Resistance ◽

High Hardness ◽

Solid Lubricants ◽

Wear Behaviour ◽

High Entropy Alloy ◽

Surface Protection ◽

High Entropy ◽

Production Route ◽

The Coefficient Of Friction ◽

Spark Plasma

High hardness and good wear resistance have been revealed for the high-entropy alloy (HEA) system AlCoCrFeNiTi, confirming the potential for surface protection applications. Detailed studies to investigate the microstructure and phase formation have been carried out using different production routes. Powder metallurgical technologies allow for much higher flexibility in the customisation of materials compared to casting processes. Particularly, spark plasma sintering (SPS) enables the fast processing of the feedstock, the suppression of grain coarsening and the production of samples with a low porosity. Furthermore, solid lubricants can be incorporated for the improvement of wear resistance and the reduction of the coefficient of friction (COF). This study focuses on the production of AlCoCrFeNiTi composites comprising solid lubricants. Bulk materials with a MoS2 content of up to 15 wt % were produced. The wear resistance and COF were investigated in detail under sliding wear conditions in ball-on-disk tests at room temperature and elevated temperature. At least 10 wt % of MoS2 was required to improve the wear behaviour in both test conditions. Furthermore, the effects of the production route and the content of solid lubricant on microstructure formation and phase composition were investigated. Two major body-centred cubic (bcc) phases were detected in accordance with the feedstock. The formation of additional phases indicated the decomposition of MoS2.

Download Full-text

High-pressure preparation of high-hardness CoCrFeNiMo0.4 high-entropy alloy

International Journal of Refractory Metals and Hard Materials ◽

10.1016/j.ijrmhm.2021.105718 ◽

2021 ◽

pp. 105718

Author(s):

Yulin Qin ◽

Yipeng Wang ◽

Shixue Guan ◽

Chuqi Wang ◽

Bo Jiang ◽

...

Keyword(s):

High Pressure ◽

High Hardness ◽

High Entropy Alloy ◽

High Entropy

Download Full-text

Phase Evolution and Microstructure Analysis of CoCrFeNiMo High-Entropy Alloy for Electro-Spark-Deposited Coatings for Geothermal Environment

Coatings ◽

10.3390/coatings9060406 ◽

2019 ◽

Vol 9 (6) ◽

pp. 406 ◽

Cited By ~ 4

Author(s):

Sigrun N. Karlsdottir ◽

Laura E. Geambazu ◽

Ioana Csaki ◽

Andri I. Thorhallsson ◽

Radu Stefanoiu ◽

...

Keyword(s):

Bulk Material ◽

Microstructural Analysis ◽

Electrochemical Corrosion ◽

High Hardness ◽

Phase Evolution ◽

Vacuum Arc ◽

High Entropy Alloy ◽

Face Centered Cubic ◽

Σ Phase ◽

High Entropy

In this work, a CoCrFeNiMo high-entropy alloy (HEA) material was prepared by the vacuum arc melting (VAM) method and used for electro-spark deposition (ESD). The purpose of this study was to investigate the phase evolution and microstructure of the CoCrFeNiMo HEA as as-cast and electro-spark-deposited (ESD) coating to assess its suitability for corrosvie environments encountered in geothermal energy production. The composition, morphology, and structure of the bulk material and the coating were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The hardness of the bulk material was measured to access the mechanical properties when preselecting the composition to be pursued for the ESD coating technique. For the same purpose, electrochemical corrosion tests were performed in a 3.5 wt.% NaCl solution on the bulk material. The results showed the VAM CoCrFeNiMo HEA material had high hardness (593 HV) and low corrosion rates (0.0072 mm/year), which is promising for the high wear and corrosion resistance needed in the harsh geothermal environment. The results from the phase evolution, chemical composition, and microstructural analysis showed an adherent and dense coating with the ESD technique, but with some variance in the distribution of elements in the coating. The crystal structure of the as-cast electrode CoCrFeNiMo material was identified as face centered cubic with XRD, but additional BCC and potentially σ phase was formed for the CoCrFeNiMo coating.

Download Full-text

A novel refractory WMoVCrTa high-entropy alloy possessing fine combination of compressive stress-strain and high hardness properties

Advanced Powder Technology ◽

10.1016/j.apt.2020.10.008 ◽

2020 ◽

Author(s):

Sujit Das ◽

P.S Robi

Keyword(s):

Compressive Stress ◽

High Hardness ◽

High Entropy Alloy ◽

Stress Strain ◽

High Entropy

Download Full-text

High Strength and Deformation Mechanisms of Al0.3CoCrFeNi High-Entropy Alloy Thin Films Fabricated by Magnetron Sputtering

Entropy ◽

10.3390/e21020146 ◽

2019 ◽

Vol 21 (2) ◽

pp. 146 ◽

Cited By ~ 7

Author(s):

Wei-Bing Liao ◽

Hongti Zhang ◽

Zhi-Yuan Liu ◽

Pei-Feng Li ◽

Jian-Jun Huang ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Magnetron Sputtering ◽

High Hardness ◽

Deformation Mechanisms ◽

High Entropy Alloy ◽

Alloy Thin Film ◽

Face Centered Cubic ◽

High Entropy ◽

Strength And Deformation

Recently, high-entropy alloy thin films (HEATFs) with nanocrystalline structures and high hardness were developed by magnetron sputtering technique and have exciting potential to make small structure devices and precision instruments with sizes ranging from nanometers to micrometers. However, the strength and deformation mechanisms are still unclear. In this work, nanocrystalline Al0.3CoCrFeNi HEATFs with a thickness of ~4 μm were prepared. The microstructures of the thin films were comprehensively characterized, and the mechanical properties were systematically studied. It was found that the thin film was smooth, with a roughness of less than 5 nm. The chemical composition of the high entropy alloy thin film was homogeneous with a main single face-centered cubic (FCC) structure. Furthermore, it was observed that the hardness and the yield strength of the high-entropy alloy thin film was about three times that of the bulk samples, and the plastic deformation was inhomogeneous. Our results could provide an in-depth understanding of the mechanics and deformation mechanism for future design of nanocrystalline HEATFs with desired properties.

Download Full-text

A robust self-stabilized electrode based on Al-based metallic glasses for a highly efficient hydrogen evolution reaction

Journal of Materials Chemistry A ◽

10.1039/c9ta11867e ◽

2020 ◽

Vol 8 (6) ◽

pp. 3246-3251 ◽

Cited By ~ 8

Author(s):

Song Ju ◽

Jingqing Feng ◽

Peng Zou ◽

Wei Xu ◽

Shunjie Wang ◽

...

Keyword(s):

Metallic Glass ◽

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Metallic Glasses ◽

Glass Ribbon ◽

High Entropy Alloy ◽

Free Standing ◽

High Entropy ◽

Metallic Glass Ribbon ◽

Nanoporous Layer

Al-based metallic glass ribbon with a nanoporous layer of high-entropy alloy is a robust advanced self-stabilized free-standing electrode for hydrogen evolution reaction.

Download Full-text

Study to Microstructure and Mechanical Properties of Mg Containing High Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.650.265 ◽

2010 ◽

Vol 650 ◽

pp. 265-271 ◽

Cited By ~ 33

Author(s):

Rui Li ◽

Jia Cheng Gao ◽

Ke Fan

Keyword(s):

Mechanical Properties ◽

Testing Machine ◽

High Hardness ◽

Material Strength ◽

High Entropy Alloy ◽

Icosahedral Quasicrystal ◽

Induction Melting ◽

High Entropy ◽

Microstructure And Mechanical Properties ◽

Thermal Analyzer

In this paper, alloys with compositions of Mgx(MnAlZnCu)100-x (x: atomic percentage; x=20, 33, 43, 45.6 and 50 respectively) were designed by using the strategy of equiatomic ratio and high entropy of mixing. Microstructure and mechanical properties of the new high entropy alloy were studied. The alloys were prepared by induction melting and then were cast in a copper mold in air. The alloy samples were examined by microhardness tester, XRD, SEM, thermal analyzer and testing machine for material strength. Alloys were composed mainly of h.c.p phase and Al-Mn icosahedral quasicrystal phases. The alloys exhibited moderate densities which were from 4.29g•cm-3 to 2.20g•cm-3, high hardness (429HV-178HV) and high compression strength (500MPa-400MPa) at room temperature. The extensibility was increased with Mg from 20at% (atomic percentage) to 50at%.

Download Full-text

Development of a TiNbTaMoZr-Based High Entropy Alloy with Low Young´s Modulus by Mechanical Alloying Route

Metals ◽

10.3390/met10111463 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1463 ◽

Cited By ~ 1

Author(s):

Juliette Normand ◽

Rocío Moriche ◽

Cristina García-Garrido ◽

Ranier Enrique Sepúlveda Ferrer ◽

Ernesto Chicardi

Keyword(s):

Milling Time ◽

Raw Materials ◽

Stress Shielding ◽

High Hardness ◽

High Entropy Alloy ◽

High Entropy ◽

Heating And Cooling ◽

Commercially Pure ◽

One Step ◽

Cp Ti

In this work, an equiatomic TiNbTaMoZr-based high-entropy alloy (HEA) has been developed by a powder metallurgy route, which consists of a process of combined one-step low-temperature mechanical milling starting from the transition metals as raw materials and a subsequent pressureless sintering. In this way, the optimized synthesized specimen, after 10 h of milling time, showed two different body-centered cubic (bcc) TiNbTaMoZr alloys, which, after sintering at 1450 °C, 1 h of dwell time and a heating and cooling rate of 5 °C min−1, it remained formed as two bcc TiNbTaMoZr-based HEAs. This material, with micrometric and equiaxed particles, and with homogeneously distributed phases, presented a Young’s modulus that was significantly higher (5.8 GPa) and lower (62.1 GPa) than that of the usual commercially pure (cp) Ti and Ti6Al4V alloy used for bone-replacement implants. It also presented similar values to those of the HEAs developed for the same purpose. These interesting properties would enable this TiNbTaMoZr-based HEA to be used as a potential biomaterial for bulk or porous bone implants with high hardness and low Young´s modulus, thereby preventing the appearance of stress-shielding phenomena.

Download Full-text