Research

12 pages, 10721 KiB

Open AccessArticle

Effect of Electron Beam Surface Modification on the Plasticity of Inconel Alloy 625

by Stefan Valkov, Georgi Kotlarski, Stoyan Parshorov, Maria Ormanova, Borislav Stoyanov, Fatme Padikova and Ivan Parshorov

Coatings 2024, 14(3), 268; https://doi.org/10.3390/coatings14030268 - 22 Feb 2024

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Abstract

In the present work, we present results on the influence of electron beam surface modification on the resistance to plastic deformation and plasticity of Inconel alloy 625. During the treatment procedure, the electron beam currents were 10 and 20 mA, corresponding to beam [...] Read more.

In the present work, we present results on the influence of electron beam surface modification on the resistance to plastic deformation and plasticity of Inconel alloy 625. During the treatment procedure, the electron beam currents were 10 and 20 mA, corresponding to beam powers of 600 W and 1200 W. The structures of the modified specimens were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The nanohardness and Young’s modulus were studied through nanoindentation experiments. The plasticity of the treated materials as well as of the untreated ones was studied through an evaluation of H³/E², which points to resistance to plastic deformation. The results obtained show that the electron beam surface modification procedure leads to a reorientation of microvolumes and the formation of a preferred crystallographic orientation. The surface treatment of the samples using an electron beam with a power of 600 W did not lead to major changes in the structures of the samples. However, the use of a beam with a power of 1200 W led to the formation of a clearly separated modified zone with a thickness in the range of 13 to 15 μm. The Young’s modulus increased from about 100 to 153 GPa in the case of electron beam surface modification using the lower-power electron beam. The application of the higher-power electron beam did not lead to a significant change in the modulus of elasticity as compared to the untreated specimen. Also, it was found that the treatment procedure pointed to a decrease in nanohardness when the maximum power of the electron beam was applied. The resistance to plastic deformation, i.e., the H³/E² ratio, showed that the ratio decreased significantly in both cases of electron beam surface modification, pointing to an improvement in the plasticity of the surface of the Inconel alloy 625. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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12 pages, 9088 KiB

Open AccessCommunication

Microstructure Features and Mechanical Properties of Casted CoFeB Alloy Target

by Ziyi Zhu, Jinjiang He, Yongjun Li, Junfeng Luo, Guojin Xu, Wenkui Yang, Dan Liu and Jiali Gao

Coatings 2024, 14(3), 255; https://doi.org/10.3390/coatings14030255 - 21 Feb 2024

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Abstract

CoFeB alloy, as a promising magneto-resistive material, has attracted extensive attention concerning the magnetic properties of its thin film in the field of magneto-resistive random memory (MRAM). Although there are many studies on the magnetic properties of CoFeB thin films, there is relatively [...] Read more.

CoFeB alloy, as a promising magneto-resistive material, has attracted extensive attention concerning the magnetic properties of its thin film in the field of magneto-resistive random memory (MRAM). Although there are many studies on the magnetic properties of CoFeB thin films, there is relatively little research on the microstructure and mechanical properties of casted CoFeB alloy. In this work, Co₂₀Fe₆₀B₂₀ (at%) alloy was fabricated through the vacuum induction melting method, and its microstructure features and mechanical performance were studied. Scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), and transmission electron microscopy (TEM) were utilized to characterize the microstructure, which consists of the coarse, needle-like Fe₂B phase that crystallizes first, the primary lamellar binary eutectic structure (Fe₂B + bcc-Fe), and the ternary eutectic structure (Fe₃B + Fe₂B + bcc-Fe phase). It is found that Fe₃B precipitates on the Fe₂B with a core–shell structure. The orientation of bcc-Fe is randomly distributed, while there are two main kinds of textures in Fe₂B: {100} <001> and Gaussian texture {110} <001>. In terms of mechanical properties, Co₂₀Fe₆₀B₂₀ alloy’s tensile strength is 140MPa, and the yield strength is 87MPa. Because the cracks are easy to generate and expand along the needle-shaped pre-crystallized Fe₂B, the plasticity of Co₂₀Fe₆₀B₂₀ alloy is very poor, only 1%. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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11 pages, 5835 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Electrically Assisted Brazing Joints of Dissimilar Aluminum and Steel Alloys

by Kun Gao, Guiqi Liu, Xiaojun Sun and Yu Wang

Coatings 2024, 14(2), 213; https://doi.org/10.3390/coatings14020213 - 07 Feb 2024

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Abstract

The microstructure and mechanical properties of electrically assisted brazing (EA-brazing) joints of aluminum alloy 6061-t6 (AA6061-t6) and S45C steel are experimentally investigated. During the EA-brazing process, an electric current is directly applied to the cylindrical specimen assembly (S45C and AA6061-t6) and fillers of [...] Read more.

The microstructure and mechanical properties of electrically assisted brazing (EA-brazing) joints of aluminum alloy 6061-t6 (AA6061-t6) and S45C steel are experimentally investigated. During the EA-brazing process, an electric current is directly applied to the cylindrical specimen assembly (S45C and AA6061-t6) and fillers of 88% Al and 12% Si (in the middle of the specimen assembly). The temperature of the specimen assembly rises rapidly to the melting point of the filler and remains nearly constant for a period of time using a pulsed electric current. Two types of EA-brazing joints are fabricated, namely Joint-0s (no temperature holding time) and Joint-12s (12 s temperature holding time). The characteristics of the intermetallic compounds (IMCs) formed at the EA-brazing joint interface are analyzed using scanning electron microscopy and energy dispersive spectrometer. Compared to Joint-0s, the Fe-rich IMCs (FeAl) are observed at the interface of Joint-12s due to the 12 s temperature holding time. In addition, the microstructural analysis shows that the thickness of the diffusion layer increases with increasing temperature holding time. The mechanical properties of the EA-brazing joints are evaluated using bending tests. The results of the mechanical test show that the strength of Joint-12s is higher than that of Joint-0s. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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29 pages, 5259 KiB

Open AccessArticle

Pull-Off Strength and Mechanical Energy Dissipation in Adhesive Contacts: Experiments and Simulations

by Iakov A. Lyashenko, Thao H. Pham and Valentin L. Popov

Coatings 2024, 14(2), 188; https://doi.org/10.3390/coatings14020188 - 31 Jan 2024

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Abstract

This study contributes to the understanding of the adhesive properties in normal contacts, providing valuable information on the influence of various factors on adhesive strength and energy dissipation. The adhesive normal contact between a steel spherical indenter and a soft sheet of elastomer [...] Read more.

This study contributes to the understanding of the adhesive properties in normal contacts, providing valuable information on the influence of various factors on adhesive strength and energy dissipation. The adhesive normal contact between a steel spherical indenter and a soft sheet of elastomer is studied experimentally. The dependencies of contact strength and mechanical energy dissipation in the complete indentation–detachment cycle on the indentation depth, the velocity of the indenter, its radius, thickness, and elastic modulus of the elastomer, the specific work of adhesion, as well as the roughness of the indenter surface, were analyzed. Experimental results are compared with simulations using the boundary element method (BEM), and the reasons leading to discrepancies between experiments and simulations are analyzed. It is shown that over a wide range of experimental parameters, the rate of mechanical energy dissipation can be estimated with sufficient accuracy using a simple empirical relation. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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11 pages, 6600 KiB

Open AccessArticle

The Influence of Boron and Carbon Addition on the Glass Formation and Mechanical Properties of High Entropy (Fe, Co, Ni, Cr, Mo)-(B, C) Glassy Alloys

by Fanli Kong, Akihisa Inoue, Fang Wang and Chuntao Chang

Coatings 2024, 14(1), 118; https://doi.org/10.3390/coatings14010118 - 16 Jan 2024

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Abstract

Coatings made from metallic glasses are a promising solution for protecting surfaces of materials in various challenging environments. From an engineering perspective, glassy alloy coatings containing carbon are of greater importance compared to those without carbon but containing boron. Despite anticipating improved coating [...] Read more.

Coatings made from metallic glasses are a promising solution for protecting surfaces of materials in various challenging environments. From an engineering perspective, glassy alloy coatings containing carbon are of greater importance compared to those without carbon but containing boron. Despite anticipating improved coating characteristics, there is no data on using high entropy glassy alloy as a coating material. In this paper, we investigated the influence of the simultaneous addition of boron and carbon elements on the glass-forming ability, thermal stability, crystallization behavior, yield strength, hardness, and corrosion resistance of high entropy (Fe, Co, Ni, Cr, Mo)-(B, C) glassy alloys. It was found that the content of boron and carbon had a significant effect on the improvements of glass-forming ability, mechanical properties, and corrosion resistance. The (Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₇₅(B_0.7C_0.3)₂₅ bulk glassy alloy exhibits high glass-forming ability, high yield strength of 3500 MPa, Vickers hardness of 1240, and the highest corrosion resistance among the alloys. We also discussed the reason for their good engineering properties, and the possibility of using high entropy glassy alloys as coating materials, in addition to the guidelines for designing high-performance multicomponent glassy alloys. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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16 pages, 20813 KiB

Open AccessArticle

Tribological and Corrosion Performance of CrAlN/CrN Coatings in Artificial Seawater under Varied Nitrogen Pressures

by Man Li, Yunjiang Yu, Changwei Zou, Canxin Tian and Yanxiong Xiang

Coatings 2023, 13(12), 2090; https://doi.org/10.3390/coatings13122090 - 15 Dec 2023

Cited by 1 | Viewed by 751

Abstract

This study employed arc ion plating technology to deposit CrAlN/CrN coatings on stainless steel substrates, adjusting deposition pressures ranging from 1.0 Pa to 4.0 Pa. A detailed analysis of the coatings’ microstructure, wear, and corrosion features was performed using X-ray diffraction, scanning electron [...] Read more.

This study employed arc ion plating technology to deposit CrAlN/CrN coatings on stainless steel substrates, adjusting deposition pressures ranging from 1.0 Pa to 4.0 Pa. A detailed analysis of the coatings’ microstructure, wear, and corrosion features was performed using X-ray diffraction, scanning electron microscopy, nanoindentation, tribometers, profilometers, and electrochemical workstations. The study revealed that the crystalline structure of the CrAlN/CrN coatings primarily consists of cubic crystals of AlN, (Cr, Al)N, and CrN. Diffraction peak intensity analysis revealed preferential orientation in the CrAlN coatings along the (111) and (200) crystal planes. As the pressure increased to 3.0 Pa, the content of Al elements peaked, and the columnar structure became denser; at this point, the H/E* ratio reached a maximum of 0.079, indicating excellent delamination and fracture resistance of the CrAlN/CrN coating at this pressure. Tests in artificial seawater environments showed that with the increase in nitrogen pressure, the friction coefficient gradually decreased, reaching its lowest at 3 Pa, approximately 0.19. The wear rate trend aligned with the friction coefficient, recorded at a mere 2.20 × 10⁻⁷ mm³/Nm. Electrochemical polarization curve tests revealed that at 3 Pa pressure, the CrAlN/CrN coating had a corrosion potential of −0.04 V, a polarization resistance of 9.28 × 10⁵ Ω·cm², and a very low corrosion current of 4.81 × 10⁻⁸ A/cm², demonstrating excellent corrosion resistance. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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15 pages, 6870 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Tribological Performance of HVAF-Sprayed Ti-6Al-4V Coatings

by Tunji A. Owoseni, Irene Ciudad de Lara, Sribalaji Mathiyalagan, Stefan Björklund and Shrikant Joshi

Coatings 2023, 13(11), 1952; https://doi.org/10.3390/coatings13111952 - 15 Nov 2023

Cited by 1 | Viewed by 923

Abstract

Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must [...] Read more.

Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must be dense to provide the required in-service functionalities, such as resistance to wear. The High Velocity Air Fuel (HVAF) thermal spray technique deposits dense coatings with reduced concern for oxide inclusions. This work presents an investigation of the microstructure, dry sliding, and solid particle erosive wear performance of four different coatings engineered through the configuration of the nozzle of an HVAF spray gun, based on the length of the nozzle and the size of the nozzle exit. A long nozzle length and wide nozzle exit mean increased inflight dwell time and reduced average inflight temperature for the sprayed particles, respectively—a reversed configuration means the opposite. The tested coatings showed a porosity of less than 2%. The sliding and erosion wear performance of the densest of the coatings compares to that of the bulk material tested under the same conditions. Electron microscopy was used to investigate the driving mechanisms for the performance of the respective coatings. The implications of the results are discussed for the potential adoption of HVAF-sprayed coatings in metal component repair. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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16 pages, 4835 KiB

Open AccessEditor’s ChoiceArticle

The Behavior of TiAlN and TiAlCrSiN Films in Abrasive and Adhesive Tribological Contacts

by Wadim Schulz, Vitalij Joukov, Florian Köhn, Wolfgang Engelhart, Veit Schier, Tim Schubert and Joachim Albrecht

Coatings 2023, 13(9), 1603; https://doi.org/10.3390/coatings13091603 - 14 Sep 2023

Cited by 1 | Viewed by 891

Abstract

Chromium and silicon are often introduced to increase the performance of TiAlN hard coatings in dry tribological contacts. The addition of Cr and Si during a high-power impulse magnetron sputtering (HiPIMS) deposition process leads to high-quality TiAlCrSiN films. In this paper, the analysis [...] Read more.

Chromium and silicon are often introduced to increase the performance of TiAlN hard coatings in dry tribological contacts. The addition of Cr and Si during a high-power impulse magnetron sputtering (HiPIMS) deposition process leads to high-quality TiAlCrSiN films. In this paper, the analysis of friction and wear of these films is conducted by oscillation tribometry under dry conditions with a subsequent mapping of the surface topography. Both abrasion- and adhesion-dominated conditions are realized using different steel counter bodies. Oscillation-frequency-dependent experiments show a significant impact of the compositional variation on friction and wear. It is shown that the TiAlCrSiN coating investigated has a higher coefficient of friction and a lower wear resistance compared to counterparts made of 100Cr6. The friction coefficient could be reduced by using a V2A counterpart. The results can be understood in terms of a reduced adhesion of both oxidic and metallic wear debris at the TiAlCrSiN surface. The study provides valuable progress towards the development of advanced cutting tools, e.g., for stainless steel. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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16 pages, 8442 KiB

Open AccessArticle

Aluminum Chromium Nitride Coating on a Laser Shock Micro-Molded Surface of E690 High-Strength Steel and Its Antifriction Mechanism

by Yupeng Cao, Haidong Bao, Weidong Shi, Zhengang Wang and Jinchao Zhang

Coatings 2023, 13(9), 1554; https://doi.org/10.3390/coatings13091554 - 05 Sep 2023

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Abstract

Aiming its analysis at the poor hardness and wear-resistance of E690 high-strength steel, and the high hardness and good wear-resistance of AlCrN-coated, combined with the laser impact micro-modeling which can store oil lubrication, this paper carries out research on the synergistic wear reduction [...] Read more.

Aiming its analysis at the poor hardness and wear-resistance of E690 high-strength steel, and the high hardness and good wear-resistance of AlCrN-coated, combined with the laser impact micro-modeling which can store oil lubrication, this paper carries out research on the synergistic wear reduction mechanism of laser impact micro-modeling AlCrN coated on the surface of E690 high-strength steel. Multi-arc ion plating technology is used to prepare the AlCrN coating on the laser-impact micro-modeling specimen; the micro-modeling AlCrN-coated specimen is subjected to a reciprocating friction test, and the hardness and residual stress of the coated surface are measured by equipment such as a residual stress meter and a microhardness tester. The microstructure and physical elements of the surface wear before and after the preparation of the coating are analyzed by scanning electron microscope (SEM), confocal three-dimensional morphometer and XRD diffractometer, respectively. The results show that the prepared AlCrN-coated materials were well-bonded to the substrate. Compared with the micro-molding-only specimens, the average friction coefficient and wear amount of the micro-molded AlCrN-coated specimens with different micro-molding densities and depths decreased compared with the micro-molded specimens; among them, the average friction coefficient of the specimens with a micro-molding density of 19.6% and a depth of 7.82 µm was 0.0936, which was the lowest. Additionally, the AlCrN coating enhances the stability of the friction process of the specimen and reduces the amount of wear of the specimen. Under the premise of ensuring the anti-wear and stability properties of the material, the best integrated friction performance was achieved at a micro-molding density of 19.6% and a depth of 24.72 µm. A synergistic wear reduction and lubrication model of micro-molding and AlCrN-coating was established. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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14 pages, 8148 KiB

Open AccessArticle

Influence of Substrate on the Tribological Behavior of Inconel 625 GMAW Overlays

by Demostenes Ferreira Filho, Daniel Souza, José Lúcio Gonçalves Júnior, Ruham Pablo Reis, Washington Martins Da Silva Junior and Amanda Figueira Tavares

Coatings 2023, 13(8), 1454; https://doi.org/10.3390/coatings13081454 - 18 Aug 2023

Cited by 3 | Viewed by 841

Abstract

This study investigates the microstructure and tribological behavior of Inconel 625 overlays applied via GMAW (Gas Metal Arc Welding) with and without a 316LSi stainless-steel intermediate layer on top of A36 steel. The microstructural characterization was conducted via FESEM with EDS. The tribological [...] Read more.

This study investigates the microstructure and tribological behavior of Inconel 625 overlays applied via GMAW (Gas Metal Arc Welding) with and without a 316LSi stainless-steel intermediate layer on top of A36 steel. The microstructural characterization was conducted via FESEM with EDS. The tribological behavior was evaluated using a tribometer in a reciprocating configuration. The results showed that the wear rate of the Inconel 625 weld overlay with the 316LSi intermediate layer was higher than without it. However, no variations were observed in terms of hardness and the friction coefficient of the Inconel 625 weld overlays. The difference in the behavior of the two coatings was justified due to the microstructure morphology found in each case and chemical composition. When applied without the intermediate layer, Inconel 625 coating’s structure was dendritic, whereas it was cellular otherwise. An increase in the amount of Nb was observed in the layer deposited over 316LSi. This rise likely led to an increase in the number of precipitates and/or Laves phase formation. Thus, the results indicated that the difference in thermal conductivity and dilution between the stainless and carbon steels modifies the morphology of the microstructure of the Inconel 625 weld overlay, decreasing wear resistance when deposited on top of the stainless steel. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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8 pages, 7672 KiB

Open AccessArticle

Effects of Coupling Action of Load and Temperature on the Lubricity of Coke Powder

by Jin Xiang, Wenan Cai and Haidong Zhang

Coatings 2023, 13(5), 939; https://doi.org/10.3390/coatings13050939 - 17 May 2023

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Abstract

By introducing the coke powder into the friction pair, the effects of load and temperature on the lubricity of coke powder at the frictional interface are studied. Before the test, the microcrystalline structures of coke powder at different temperatures are characterized by X-ray [...] Read more.

By introducing the coke powder into the friction pair, the effects of load and temperature on the lubricity of coke powder at the frictional interface are studied. Before the test, the microcrystalline structures of coke powder at different temperatures are characterized by X-ray diffraction (XRD). After the test, the friction surfaces are observed by electron microscope and energy spectrum, the oxide compositions of friction surface are characterized by XRD, and the lubrication mechanism of coke powder is investigated. The results show that at RT (room temperature), as the load increases, the forming of the powder layer gradually deteriorates. When the load is 5 MPa, at a low temperature, the powder layer is thicker, and the coke powder exhibits better lubricity. In contrast, at a high temperature, affected by the temperature, the lubricity of coke powder declines, and the friction coefficient is higher. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)

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