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Open AccessArticle

Corrosion Behavior and Comprehensive Evaluation of Al_0.8CrFeCoNiCu_0.5B_0.1 High-Entropy Alloy in 3.5% NaCl Solution

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Lubricants 2023, 11(7), 282; https://doi.org/10.3390/lubricants11070282 - 30 Jun 2023

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Abstract

In this study, Al_0.8CrFeCoNiCu_0.5B_0.1 high-entropy alloy coating was prepared on the surface of 5083 aluminum alloy using laser cladding technology. The corrosion behavior of the coating and substrate in 3.5% NaCl solution was analyzed using experimental methods, including [...] Read more.

In this study, Al_0.8CrFeCoNiCu_0.5B_0.1 high-entropy alloy coating was prepared on the surface of 5083 aluminum alloy using laser cladding technology. The corrosion behavior of the coating and substrate in 3.5% NaCl solution was analyzed using experimental methods, including polarization curves and electrochemical impedance spectroscopy. The corrosion current density of Al_0.8CrFeCoNiCu_0.5B_0.1 coating is 2.04 × 10⁻⁷ A/cm ². The passivation range width reaches 2.771 V, and these polarization test results are superior to the substrate. The Al_0.8CrFeCoNiCu_0.5B_0.1 coating exhibited selective corrosion behavior, with the Cu-rich FCC1 phase and Cr-poor phase being susceptible to corrosion, leading to localized pitting and intergranular corrosion traces, but the corrosion did not spread extensively. The intergranular distribution of Cu is the main reason for the intergranular corrosion trace features. In contrast, the substrate exhibited overall corrosion. The Nyquist plot of the Al_0.8CrFeCoNiCu_0.5B_0.1 coating consisted of a single capacitive semicircle arc in the high-frequency region with a larger radius than the substrate. In conclusion, using the Al_0.8CrFeCoNiCu_0.5B_0.1 high-entropy alloy as a coating can significantly improve the corrosion resistance of the 5083 aluminum alloy substrate. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

Microstructure and Wear Performance of CeO₂-Modified Micro-Nano Structured WC-CoCr Coatings Sprayed with HVOF

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Chidambaram Seshadri Ramachandran

Lubricants 2023, 11(5), 188; https://doi.org/10.3390/lubricants11050188 - 25 Apr 2023

Cited by 1 | Viewed by 887

Abstract

Rare earth elements have been widely utilized in material manufacturing to enhance properties in various ways. In order to obtain the WC-10Co4Cr coating with uniform distribution of rare earths, CeO₂-modified powder was prepared by mixing 1 wt.% nano-sized CeO₂ during [...] Read more.

Rare earth elements have been widely utilized in material manufacturing to enhance properties in various ways. In order to obtain the WC-10Co4Cr coating with uniform distribution of rare earths, CeO₂-modified powder was prepared by mixing 1 wt.% nano-sized CeO₂ during the initial ball-milling of the powder fabrication process. Bare and CeO₂-modified WC-10Co4Cr coatings were deposited via high velocity oxygen fuel spraying to investigate the impact of CeO₂ modification on the coating’s microstructure, mechanical properties and abrasive wear performance. The results show that the addition of CeO₂ increased the interface energy, inhibiting the formation of the Co₃W₃C phase during the powder sintering process, as well as the W₂C phase and CoCr alloy during the high-velocity oxy-fuel (HVOF) process. This led to a significantly decreased porosity and higher concentration of undissolved Cr-rich areas. The microhardness and fracture toughness of the CeO₂-modified coating were 1230 HV_0.3 and 5.77 MPam^1/2, respectively. The abrasive wear resistance of the CeO₂-modified coating was only 70.9% of that of the unmodified coating. Due to the weak cohesive strength between WC and Cr, Cr-rich areas were preferentially removed, resulting in an increased wear rate in the CeO₂-modified coating. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

Microstructure and Wear Resistance of Ni–WC–TiC Alloy Coating Fabricated by Laser

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Lubricants 2023, 11(4), 170; https://doi.org/10.3390/lubricants11040170 - 10 Apr 2023

Cited by 2 | Viewed by 866

Abstract

In this study, a Ni–WC–TiC alloy coating was fabricated by laser to improve the wear resistance and service life of Cr12MoV die steel. The microstructures and phases of the coating were analyzed by a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), [...] Read more.

In this study, a Ni–WC–TiC alloy coating was fabricated by laser to improve the wear resistance and service life of Cr12MoV die steel. The microstructures and phases of the coating were analyzed by a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The properties of the coating were tested by a hardness and friction wear tester. The results show that the coating has a good metallurgical bond with the substrate. The microstructures from top to bottom are mainly equiaxed crystal, columnar dendrite, and cellular dendrite. Combined with the physical phase analysis and elemental distribution of the coating, there are some phases, such as γ~(Fe, Ni), Cr₂₃C₆, WC, TiC, Fe₃W₃C, and Cr₂Ti. Compared with the Cr12MoV steel substrate, the Ni–WC–TiC alloy coating has good properties of hardness and wear resistance. In the coating, the background region of the grains is γ~(Fe, Ni). From the EDS results, it can be seen that there are some rod-like particles, Cr₂₃C₆, which are uniformly distributed on the top of the coating. Some W and Ti carbides form in grains. The addition of TiC particles improves the WC particles refinement. The highest hardness of the coating is 770.7 HV_0.5, which is approximately 3.3 times higher than that of the substrate. The wear volume is 0.26 mm³, or approximately 8.6% of the substrate, which is contributed to the reinforced phases and finer microstructure of the coating. The wear volumes of the Cr12MoV substrate are 1.8 and 4.5 mm³ at 20 and 60 min, respectively. While the wear volumes of the Ni–WC–TiC coating are 0.2 and 0.7 mm³ at 20 and 60 min, respectively. The increased amplitude of the coating’s wear volume is smaller than that of the substrate. The results show that this Ni–WC–TiC alloy coating is helpful for improving the properties and service life of Cr12MoV die steel. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

‘Triangle Ester’ Molecules as Blending Components in Mineral Oil: A Theoretical and Experimental Investigation

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Lubricants 2023, 11(3), 144; https://doi.org/10.3390/lubricants11030144 - 17 Mar 2023

Cited by 1 | Viewed by 1010

Abstract

The present work explored the use of fatty acid ‘Triangle ester’ molecules (Epoxidized Ester (EE), and Thiirane Ester (TE)) as antifriction and antiwear additives at varying levels for Group I and Group II mineral base oils using the standard ASTMD-4172B four-ball test. Relative [...] Read more.

The present work explored the use of fatty acid ‘Triangle ester’ molecules (Epoxidized Ester (EE), and Thiirane Ester (TE)) as antifriction and antiwear additives at varying levels for Group I and Group II mineral base oils using the standard ASTMD-4172B four-ball test. Relative to neat base oil, EE blends showed improved antifriction by ~61% and ~42% and antiwear properties by ~32% and ~41% in Group I and Group II base oils, respectively, while the TE blends showed friction reduction by ~65% and ~40% and wear reduction by ~93% and ~50% relative to the same neat base stock. Time evolution of the ‘Triangle ester’ molecules and their blends with mineral oil (modeled as hexadecane) w.r.t. conformational changes, adsorption energy, intermolecular energy, and effect of the applied stress were estimated theoretically using MD simulations. Further, optimized levels of these additives were explored for their effectiveness as a blending component for commercial engine oil (CEO) and could reduce the friction and wear of CEO by ~50% and ~30%, respectively. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

Effect of Y on Microstructure and Properties of Al_0.8FeCrCoNiCu_0.5 High Entropy Alloy Coating on 5083 Aluminum by Laser Cladding

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Lubricants 2023, 11(2), 50; https://doi.org/10.3390/lubricants11020050 - 30 Jan 2023

Cited by 1 | Viewed by 856

Abstract

To improve the surface properties of 5083 aluminum, Al_0.8FeCrCoNiCu_0.5Y_x (x = 0, 0.05, 0.1, and 0.2) high-entropy alloy coatings were prepared by laser cladding. The phase structure and microstructure of the Al_0.8FeCrCoNiCu_0.5Y_x coatings [...] Read more.

To improve the surface properties of 5083 aluminum, Al_0.8FeCrCoNiCu_0.5Y_x (x = 0, 0.05, 0.1, and 0.2) high-entropy alloy coatings were prepared by laser cladding. The phase structure and microstructure of the Al_0.8FeCrCoNiCu_0.5Y_x coatings were characterized by XRD and SEM. The tribological properties of the coating were tested by a friction and wear tester. An electrochemical workstation tested the corrosion resistance of the coating. The results show that when Y content is less than 0.2, the Al_0.8FeCrCoNiCu_0.5Y_x coating is in the FCC1, BCC1, and BCC2 phases. When Y is added to 0.2, the coating appears rich in the Y phase. With the increased Y content, the hardness of the coating can increase. The average hardness of Y₀, Y_0.05, Y_0.1, and Y_0.2 are 479HV_0.2, 517HV_0.2, 532HV_0.2, and 544HV_0.2, respectively. Microstructure evolution leads to an increase in the hardness of the coating. The effect of Y on the wear resistance of the Al_0.8FeCrCoNiCu_0.5Y_x coatings is consistent with the hardness. Al_0.8FeCrCoNiCu_0.5Y_0.2 coating has the lowest wear rate, at is 8.65 × 10⁻⁶ mm³/Nm. The corrosion current density of Al_0.8FeCrCoNiCu_0.5Y_0.05 and Al_0.8FeCrCoNiCu_0.5Y_0.1 coatings is in the order of 10⁻⁸, which is less than Al_0.8FeCrCoNiCu_0.5Y_0.2 and Al_0.8FeCrCoNiCu_0.5. The performance of each component coating is superior to that of the substrate. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

The Effects of Interval Uncertainties on Dynamic Characteristics of a Rotor System Supported by Oil-Film Bearings

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Lubricants 2022, 10(12), 354; https://doi.org/10.3390/lubricants10120354 - 08 Dec 2022

Cited by 2 | Viewed by 1265

Abstract

Rotating systems equipped with oil-film bearings are critical and common in many industrial machines. There are various non-random uncertainties in such fluid-lubricated dynamic systems. It is important to quantify the effects of uncertainties without adequate statistical information on the dynamics of rotor-bearing systems. [...] Read more.

Rotating systems equipped with oil-film bearings are critical and common in many industrial machines. There are various non-random uncertainties in such fluid-lubricated dynamic systems. It is important to quantify the effects of uncertainties without adequate statistical information on the dynamics of rotor-bearing systems. In this paper, a rotor system with oil-film bearings at both ends is investigated considering many interval uncertainties. The rotating system is modeled in a deterministic sense. The Chebyshev interval method is used to track the propagation of different uncertainties. Deviations in the steady state responses, time history, and shaft orbits are calculated and comparatively discussed. Influence patterns of different interval parameters and dispersions in various dynamics are presented in detail. It is found that there can be global and local impacts as well as cumulative effects caused by multi-source uncertainties. The findings of the present study could be helpful for a more insightful dynamic analysis of rotor-bearing systems as well as their optimal design and maintenance. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

Evaluation of Surface Roughness, Tool Wear and Chip Morphology during Machining of Nickel-Based Alloy under Sustainable Hybrid Nanofluid-MQL Strategy

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Mayur A. Makhesana

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Kaushik M. Patel

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Prashant J. Bagga

Lubricants 2022, 10(11), 315; https://doi.org/10.3390/lubricants10110315 - 18 Nov 2022

Cited by 2 | Viewed by 1196

Abstract

Nickel-based super alloys exhibit high strength, oxidation and corrosion resistance; however, the machining of these alloys is a challenge that can be overcome with effective cooling/lubrication techniques. The use of a minimum quantity lubrication (MQL) technique is limited to lower cutting parameters due [...] Read more.

Nickel-based super alloys exhibit high strength, oxidation and corrosion resistance; however, the machining of these alloys is a challenge that can be overcome with effective cooling/lubrication techniques. The use of a minimum quantity lubrication (MQL) technique is limited to lower cutting parameters due to the tremendous heat produced during the machining of Inconel 718. Sustainable and eco-friendly machining of Inconel 718 can be attained using MQL and lubricants based on nanofluids because of their improved heat transfer capabilities. For that purpose, the performance of hybrid nanofluid-MQL is examined. In this novel study, graphene and hexagonal boron nitride (hBN) nanoparticles are reinforced with palm oil and delivered to the machining interface using an MQL setup. The machining experiments are performed under the conditions of dry, wet, MQL and MQL with graphene/hBN deposited in palm oil. The machining performance under selected cutting conditions is assessed by analyzing the surface roughness, tool wear, chip morphology and surface quality of the machined workpiece. A comparison of results showcased the effectiveness of hybrid nanofluid-MQL with improvement in surface finish, reduction in tool wear and favorable chip forms concerning all other machining conditions. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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Open AccessArticle

Cavitation Morphology Study between Hemispherical Textured Rotating Friction Pairs

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Lubricants 2022, 10(10), 249; https://doi.org/10.3390/lubricants10100249 - 03 Oct 2022

Cited by 2 | Viewed by 1309

Abstract

A non-direct contact rotary interface uses a viscous fluid as the lubricant working medium. Because the oil film friction coefficient formed is extremely small, so it has great application potential in sealing, fluid transmission, thermosolutal convection, and bionics. Research on mechanical seals, wet [...] Read more.

A non-direct contact rotary interface uses a viscous fluid as the lubricant working medium. Because the oil film friction coefficient formed is extremely small, so it has great application potential in sealing, fluid transmission, thermosolutal convection, and bionics. Research on mechanical seals, wet clutches, and dynamic load bearing have proven that micro-textures can effectively improve friction and lubrication performance. However, when the fluid flows through the texture boundary, pressure disturbances can induce hydrodynamic cavitation. A pair of rotating disks are selected as our research objects. From the simulation and experiment research, we found that cavitation volume does not always increase with an increase in the texture rate, and cavitation always occurs preferentially at the outer diameter, so it is necessary to avoid machining the texture structure at the outer diameter of the mechanical seal end. Once the conditions for cavitation are met, a complete cavity is formed in approximately 0.015 s. The study also verifies that the cavitation gas originates from the phase change of the oil. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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