Alloy Composite Coatings Research Articles

The effect of annealing on the microstructure and wear performance of laser-clad high-entropy alloy composite coatings for monorail crane braking systems

Laser cladding was utilized to fabricate WC ceramic particle-reinforced CoCrFeMnNi high-entropy alloy (HEA) composite coatings, with an investigation into the influence of annealing heat treatment on the microstructure and wear behavior of the composite coatings. The HEA composite coatings with a WC particle content of 30 wt% primarily consist of a face-centered cubic (FCC) solid solution phase, various M6C carbides with blocky, fishbone, and dendritic morphologies, and incompletely melted WC ceramic particles. The microstructure of the composite coatings remains stable up to a temperature of 570°C. After annealing at 600°C, the microstructure transforms into a typical dendritic morphology with rod-like carbides precipitating from the solid solution and discontinuously distributed in the interdendritic regions. Due to the annealing softening effect, the microhardness of the coating decreases from 488.1 HV0.3 to 443.1 HV0.3. Following annealing at a high temperature of 800°C, recrystallization leads to a refined equiaxed grain microstructure, with precipitated carbides continuously distributed along the grain boundaries, forming a network. The combined effects of precipitation hardening and fine grain strengthening result in an increase in the microhardness of the coating to 568.6 HV0.3 after annealing at 800°C. As the annealing temperature increases, the wear rate of the WC particle-reinforced CoCrFeMnNi HEA composite coatings also increase. The wear mechanism for the unannealed coating is oxidative wear, and the reduction in hardness leads to adhesive phenomena in the coating after annealing at 600°C. The network of carbides reduces the ductility of the HEA and also the toughness of the oxide film, resulting in the highest wear rate for the coating annealed at 800°C, reaching 38.636×10−6 mm3/(N·m). This study provides valuable insights for the fabrication of advanced wear-resistant coatings.

Wear, corrosion and cavitation erosion behavior of WC-reinforced FeCrNiMnAl ceramic-high entropy alloy composite coatings by laser cladding

FeCrNiMnAl/WC ceramic-high entropy alloy (HEA) composite coatings with various WC content are prepared on 304 stainless steel (304 SS) by laser cladding (LC). Experimental results show that residual tensile stress of coatings increases with the addition of WC content, and excessive addition of WC leads to cracking in 15WC and 20WC. All coatings are composed of BCC and WC duplex, and the addition of WC particles significantly refines grain size of the coatings. Compared with FeCrNiMnAl HEA coating, the coatings with WC addition exhibit improving mechanical properties and wear resistance due to the combined effect of multiple strengthening mechanisms. Among the tested coatings, 10WC exhibits the highest cavitation erosion (CE) resistance due to its excellent mechanical properties and corrosion resistance.

Effect of ZrO2 Particles on the Microstructure and Ultrasonic Cavitation Properties of CoCrFeMnNi High-Entropy Alloy Composite Coatings

CoCrFeMnNi-XZrO2 (X is a mass percentage, X = 1, 3, 5, and 10) high-entropy alloy composite coatings were successfully prepared on 0Cr13Ni5Mo martensitic stainless steel substrates using laser cladding technology. The phase composition, microstructure, mechanical properties, and cavitation erosion behavior of the composite coatings under different contents of ZrO2 were studied. The mechanism of ZrO2 particle-reinforced cavitation corrosion resistance was studied using ABAQUS2023 finite element software. The results show that the phase structure of the composite coating organization is composed of FCC phase reinforced by ZrO2 phase. The addition of ZrO2 causes lattice distortion. The coatings have typical branch crystals and an equiaxed crystal microstructure. With the increase in ZrO2 content, the microhardness of the composite coatings gradually increases. When X = 10%, the coating’s microhardness reached 348 HV, which was 95.53% higher than the high-entropy alloys without ZrO2 added. Adding ZrO2 can prolong the incubation period of high-entropy alloys; the high-entropy alloy composite coating with 5 wt.% ZrO2 exhibited the best cavitation resistance, with a cumulative volume loss rate of only 15.74% of the substrate after 10 h of ultrasonic cavitation erosion. The simulation results indicate that ZrO2 can withstand higher stress and deformation in cavitation erosion, reduce the degree of substrate damage, and generate higher compressive stress on the coating surface to cope with cavitation erosion.

Effect of graphene content on the tribological and corrosion behavior of high-speed-laser-clad high-entropy-alloy composite coatings

To repair oil drill pipe joints that have failed owing to dry wear and tribocorrosion, graphene-reinforced CoCrFeMo0.5NiTi0.5 high-entropy alloy composite coatings (HEACCs) were developed through high-speed laser cladding. The HEACC containing 1.5 wt% graphene exhibited dry wear and tribocorrosion rates that were 59.18 % and 32.20 % of those observed in the high-entropy alloy coating, respectively. The HEACC exhibited a corrosion current density of 2.475 × 10−7 A/cm2. The HEACC containing 1.5 wt% graphene underwent progressive damage during dry wear owing to the combined effects of abrasive wear, which created furrows; adhesive wear, which led to flaking; and oxidative wear, which formed oxide layers. During tribocorrosion, chloride ions exacerbated surface damage caused by hard abrasives and asperities, intensifying corrosive–abrasive wear interactions.

Microstructure and wear property of (TiN + NbC) double ceramic phase-reinforced in FeCrNiCoAl high-entropy alloy coating fabricated by laser cladding

This study delves into the influence of TiN and NbC ceramic particles on the phase structure, grain organization, microhardness, and wear resistance of FeCoNiCrAl High-Entropy Alloy (HEA) composite coatings produced through laser cladding. The integration of ceramic particles induced a dual BCC solid-solution phase structure (B2+BCC), with the formation of a TiNb phase upon the melting and interaction of TiN and NbC in the melt pool. The ceramic particles significantly modified the grain structure of the HEA coatings, disrupting the Columnar-to-Equiaxed Transition (CET) and favoring the emergence of equiaxed grains. The TiN particles induced a substantial refinement of grain size, albeit unevenly, while NbC had a milder effect. The combined presence of TiN and NbC particles resulted in a more uniform grain refinement, enhancing the mechanical properties of the coatings. Notably, the (TiN + NbC)/HEAs composite coating demonstrated superior mechanical performance under the synergistic effect of both ceramic particles. The average microhardness value increased by 55.80 % compared to 17-4Ph stainless steel, and the wear rate was reduced by 88.38 %, with the wear mechanism primarily involving abrasive and oxidative wear.

Optimization of surface oxide chemistry for enhanced corrosion resistance of AlMnFeCoNi – Carbon nanotube composite coatings

AlMnFeCoNi high entropy alloy (HEA) composite coatings with different volume fractions of carbon nanotubes (CNTs) (from electrolyte bath with 2.5, 4, 5, 15, 17.5, 20 mg/L of CNT) were electrodeposited onto mild steel. Corrosion rate of HEA-CNT coatings exhibited non-monotonic variation with increasing CNT volume fraction. Corrosion resistance initially increased and then decreased with increasing CNT addition. Highest corrosion resistance exhibited by coating produced from 5 mg/L of CNT was due to higher surface uniformity, least surface roughness (732 ± 2.92 nm), induced hydrophobicity (115.44 ± 0.29˚) and presence of stable passive oxide films (Al3+, Co2+, Fe3+).

Effect of Si3N4 content on microstructure and frictional-wear properties of MoNbTaWTi refractory high entropy alloy composite coatings

To address the shortcomings of the Ti-6Al-4 V alloy, characterized by low surface hardness and inadequate friction and wear properties, a composite coating of in-situ TiN reinforced MoNbTaWTi refractory high-entropy alloy was developed using laser cladding technology on Ti-6Al-4 V substrate. The effects of different Si3N4 contents on coating organization and wear resistance are discussed. Analysis through X-ray diffractometry (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) revealed that the composite coating primarily consisted of the body-centered cubic (BCC) phase and an in-situ TiN enhanced phase. Notably, at a Si3N4 content of 2.0 wt%, the average microhardness at the coating's top surface reached 808.67 HV0.1, surpassing that of the substrate by 2.33 times. The friction coefficient was reduced to 0.3009, representing only 59.01 % of the Ti-6Al-4 V substrate. Furthermore, the wear weight loss measured at 0.4×10−2 mm3 was a mere 22.35 % of the Ti-6Al-4 V substrate, with the wear area accounting for only 0.27 % of the Ti-6Al-4 V substrate. Results demonstrated that utilizing the in-situ reaction between Ti element and Si3N4, the in-situ generated TiN reinforced phase significantly enhanced the hardness and wear resistance of the coating.

Microstructure evolution, wear and corrosion behavior of WC reinforced CoCrFeNiMn high-entropy alloy composite coatings by induction cladding

In this study, CoCrFeNiMn high entropy alloy (HEA) composite coatings reinforced with different WC particle contents were prepared by induction cladding technology for the first time. The effects of WC particle contents (0–70 wt%) on the microstructure, hardness, wear resistance and corrosion resistance of the coatings were analyzed. The results showed that the coatings prepared by induction cladding exhibited good metallurgical bonding with the substrate. The addition of WC particles led to grain refinement in the CoCrFeNiMn HEA together with second-phase strengthening and solid solution strengthening, improving the microhardness of the coatings. Compared to the average hardness value of 183 HV0.5 for the CoCrFeNiMn HEA coating, the composite coating with 60 wt% WC particle content exhibited the highest average hardness value of 679 HV0.5. The addition of WC particles significantly enhanced the wear resistance of the composite coating, with wear mechanisms including adhesive wear, abrasive wear, fatigue wear and oxidation wear. The composite coating with 60 wt% WC particle content demonstrated outstanding wear resistance, with a specific wear rate value of 0.491 × 10−6 mm3N−1 m−1, representing a reduction of approximately 670 times compared to the CoCrFeNiMn HEA coating. However, the addition of WC particles caused uneven potential distribution within the composite coatings, leading to galvanic corrosion. The WC particles and precipitated carbides increased the defects in the passive film, thus reducing the corrosion resistance of the composite coatings.

Phase composition, surface chemistry and electrochemical studies of electrodeposited AlMnFeCuNi high entropy alloy composite coatings incorporated with carbon nanotubes

AlMnFeCuNi high entropy alloy (HEA) coatings were electrodeposited onto mild steel substrate with and without incorporation of carbon nano tubes (CNT). This paper focused on the morphology, hardness, wear and corrosion behaviour for as deposited HEA and HEA-CNT coatings. Both the coatings constituted simple solid solution with face-centered cubic (FCC) structure. The addition of carbon nano tubes in the HEA coatings as revealed by scanning electron microscopy showed more smaller granules and compact morphology with least coating thickness value (5 ± 0.35 μm). Enhanced Anti-wear performance results in higher hardness and lower coefficient of friction. The presence of CNTs resulted improvised corrosion resistant properties in 3.5% NaCl corrosive media. The formation of more protective oxides such as Alox +3, Mnox +2 and Feox +3 on passive oxide layer in HEA-CNT coatings acted as a barrier, protected it from corrosion.

A Comparative Study between a Thermal Spray CoCrFeMnNi0.8V/WC-Co High Entropy Alloy Composite Coating and Plain CoCrFeMnNi0.8V and WC-Co Thermal Spray Coatings

High entropy alloys (HEAs) have emerged as a frontier in surface engineering, challenging the status quo of traditional alloy systems with their exceptional mechanical properties and corrosion resistance. This study investigates the CoCrFeMnNi0.8V HEA, both as a standalone alloy and in a composite with WC-Co, to evaluate their potential as innovative surface coatings. The CoCrFeMnNi0.8V alloy, enriched with vanadium, demonstrates a unique microstructure with enhanced hardness and wear resistance, while the addition of WC-Co particles contributes to improved toughness and durability. By employing High Velocity Oxy-Fuel (HVOF) thermal spray techniques, coatings are deposited onto steel substrates and subjected to rigorous microstructural characterization, wear, and corrosion resistance testing. The results reveal that the CoCrFeMnNi0.8V coating exhibits impressive corrosion resistance in chloride-rich environments. The composite coating leverages the synergy between the HEA’s inherent corrosion resistance and WC-Co’s wear resistance, striking a balance that suits demanding applications. With optimized processing conditions, the composite WC-Co-reinforced high entropy alloy coating could offer a significant advancement in protective coatings technology, especially for maritime and other corrosive settings. This work not only underscores the versatility of HEAs in surface engineering applications but also opens avenues for the development of new material mixtures.

Corrosion resistance of VC-reinforced Fe-based SMA coatings by laser cladding

The corrosion resistance of 42CrMo steel is insufficient to meet the demands in the marine environment, despite its widespread application in bearings and other fields. Herein, Fe-Mn-Si-Cr-Ni-χ(VC) shape memory alloy (SMA) composite coatings were successfully fabricated on the surface of 42CrMo steel using laser cladding technology. The results present that the coatings are mainly composed of γ austenite (fcc) phase and ε martensite (hcp) phase. Based on research findings, the incorporation of VC has been found to promote the γ → ε martensite phase transition in shape memory alloys. Simultaneously, electrochemical tests were conducted on 42CrMo substrate and SMA coating in 3.5 wt% NaCl solution. It was found that the coatings doped with an appropriate amount of VC could effectively enhance its corrosion resistance. When the doping amount of VC reaches 1.5 wt%, the charge transfer resistance (Rct) is significantly higher than that of the 42CrMo substrate and the pure SMA coating, as well as that of the coating doped with 2.0 wt% VC, reaching 21, 2.6, and 3.3 times of them, respectively. The charge transfer resistance Rct of LS1.5 is much higher than that of 42CrMo, LS0, and LS2.0, reaching 21, 2.6, and 3.3 times, respectively. Additionally, the maximal polarization resistance (Rp) of coatings achieves 4.39 times that of 42CrMo. This study points out that VC can efficiently boost the corrosion resistance of SMA composite coatings and may have uncovered a novel approach for improving the surface corrosion resistance of medium carbon steel.

Progress on the Properties of Ceramic Phase-Reinforced High-Entropy Alloy Composite Coatings Produced via Laser Cladding

The production of ceramic phase-reinforced high-entropy alloy composite coatings with excellent mechanical properties, high-temperature oxidation resistance, and corrosion resistance via laser cladding is a new hotspot in the field of surface engineering. However, as high-entropy alloys have a wide range of constituent systems and different kinds of ceramic particles are introduced in different ways that give the coatings unique microscopic organization, structure, and synthesized performance, it is necessary to review the methods of preparing ceramic phase-reinforced high-entropy alloys composite coatings via laser cladding. In this paper, the latest research progress on laser cladding technology in the preparation of ceramic phase-reinforced high-entropy alloy composite coatings is first reviewed. On this basis, the effects of ceramic particles, alloying elements, process parameters, and the microstructure and properties of the coatings are analyzed with the examples of the in situ generation method and the externally added method. Finally, research gaps and future trends are pointed out, serving as a reference for the subsequent research, application, and development of the preparation of ceramic phase-reinforced high-entropy alloy composite coatings.

Effects of Zr-based and Ni-based amorphous alloy powders on the wear resistance and corrosion behavior of polyurethane composite coatings on aluminum alloys

In this study, we present a new strategy for modifying polyurethane coatings to improve the surface performance of 6061 aluminum alloys, that is, Zr-based and Ni-based amorphous alloys were used as modified fillers. The addition of amorphous alloys resulted in alterations to the intermolecular forces among N-H bonds in the hard segments and the H-bond strength of CO bonds in the urea groups. The introduction of amorphous particles disordered the original arrangement of the fillers and gave rise to near-ring structures, which typically has a positive effect on the overall performance of the coatings. Under the synergistic effect of amorphous alloy properties and H-bond strength, hardness and wear resistance increased with increasing amorphous content. The coatings exhibit a certain degree of stealth performance, and the addition of amorphous alloys substantially improves the corrosion resistance of the coatings. Among the polyurethane/amorphous alloy composite coatings, the one containing 50 vol% Zr-based amorphous alloy has the best overall performance. Compared to previous researches, we pioneered the utilization of outstanding properties of Zr-based and Ni-based amorphous alloys to improve polyurethane coatings. This novel composite coating has great potential to be used as a corrosion-resistant coating and to be combined with good mechanical properties.

Effect of WC on the microstructure and mechanical properties of laser-clad AlCoCrFeNi2.1 eutectic high-entropy alloy composite coatings

AlCoCrFeNi2.1/WC eutectic high-entropy alloy composite coatings were prepared on a 316 L stainless steel substrate via the laser cladding method. The effects of the WC content on the phase composition, microstructure, and mechanical properties of the composite coatings were investigated. The results revealed that the laser-clad AlCoCrFeNi2.1/WC eutectic high-entropy alloy composite coating mainly consisted of FCC and BCC phases. As the WC content increased from 0 wt% to 30 % wt%, the Cr7C3 and Cr21W2C6 phases were gradually precipitated from the composite coating. Consequently, the microhardness of the composite coating increased from 318.6 to 572.3 HV1.0. The strengthening mechanism of composite coatings mainly comprised solid solution strengthening, second-phase strengthening, and fine-grain strengthening. Additionally, the high dislocation density, caused by rapid condensation during the laser cladding process, contributed to the improvement in the coating hardness. Wear experiments revealed a significant improvement in the wear resistance of the composite coating with increasing WC content. The composite coating with 30 wt% WC exhibited the highest hardness and wear resistance with an average friction coefficient of 0.535, as well as a wear rate and wear volume loss of 4.4 × 10−7 mm3N−1 mm−1 and 5.44 mm3, respectively.

The Interplay of Thermal Gradient and Laser Process Parameters on the Mechanical Properties, Geometrical and Microstructural Characteristics of Laser-Cladded Titanium (Ti6Al4V) Alloy Composite Coatings

With the development of laser surface modification techniques like direct laser metal deposition (DLMD), titanium alloy (TI6Al4V) may now have its entire base metal microstructure preserved while having its surface modified to have better characteristics. Numerous surface issues in the aerospace industry can be resolved using this method without changing the titanium alloy’s primary microstructure. As a result, titanium alloy is now more widely used in sectors outside of aerospace and automotive. This is made possible by fabricating metal composite coatings on titanium alloys using the same DLMD method. Any component can be repaired using this method, thereby extending the component’s life. The experimental process was carried out utilizing a 3000 W Ytterbium Laser System at the National Laser Centre of the CSIR in South Africa. Through the use of a laser system, AlCuTi/Ti6Al4V was created. The characterization of the materials for grinding and polishing was performed according to standard methods. There is a substantial correlation between the reinforcement feed rate, scan speed, and laser power components. Due to the significant role that aluminum reinforcement played and the presence of aluminum in the base metal structure, Ti-Al structures were also created. The reaction and solidification of the copper and aluminum reinforcements in the melt pool produced the dendritic phases visible in the microstructures. Compared to the base alloy, the microhardness’s highest value of 1117.2 HV1.0 is equivalent to a 69.1% enhancement in the hardness of the composite coatings. The enhanced hardness property is linked to the dendritic phases formed in the microstructures as a result of optimized process parameters. Tensile strengths of laser-clad ternary coatings also improved by 23%, 46.2%, 13.1%, 70%, 34.3%, and 51.7% when compared to titanium alloy substrates. The yield strengths of laser-clad ternary coatings improved by 19%, 46.7%, 12.9%, 69.3%, 34.7%, and 52.1% when compared to the titanium alloy substrate.

Microstructure and properties of diamond/Ni-based alloy composite coatings by induction brazing

Microstructure and properties of diamond/Ni-based alloy composite coatings by induction brazing

Microstructure and tribological properties of in-situ MxB reinforced CoCrFeNi HEA composites prepared by laser cladding

The CoCrFeNiTixB2x (x = 0, 0.1, 0.2, and 0.3) high entropy alloy (HEA) composite coatings were prepared on Q235 substrates by laser cladding. The microstructure, grain orientation, precipitated phase and tribological properties of the coatings were investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-speed reciprocating wear friction tester, respectively. The results show that TiB, Cr2B, FeCrB and (FeCr)2B phases were in-situ formed in the composite coatings. The microstructures of the coatings are refined and the hardness increases with the addition of Ti and B elements. The grain orientation of all coatings is random. The orientation relationships between the HEA matrix and Cr2B is HEA matrix (002) // Cr2B (1̅3̅1̅), HEA matrix [5̅10] // Cr2B [013̅]. The composite coating exhibits the best wear resistance when the x of CoCrFeNiTixB2x is 0.2. The primary strengthening mechanisms of Ti and B doped CoCrFeNi HEAs are the synergistic effect of solid solution strengthening, second phase strengthening and fine grain strengthening.

Microstructure and tribological performance of ultra-high speed laser-cladded AlCrCoFeNi2.1-xTiB2 (x = 0, 0.5, 1.0, 1.5 and 2.0 wt%) high-entropy alloy coatings

AlCoCrTeNi2.1- xTiB2 (x = 0, 0.5, 1.0, 1.5 and 2.0 wt%) high-entropy alloy (HEA) composite coatings were prepared on 304 stainless steel by ultra-high speed laser cladding. The microstructure, microhardness and tribological performance of HEA composite coatings were studied in detail. The results showed that HEA composite coatings all mainly consisted of BCC and FCC solid solution phase, and the addition of TiB2 didn’t change the phase structure of HEA composite coatings. The addition of TiB2 improves the microhardness of HEA composite coating. When x = 2.0 wt%, the microhardness of HEA composite coating reaches the maximum value (331.3 ± 5.0 HV), which is nearly 1.5 times that of 304 stainless steel. Accordingly, the wear resistance of the AlCoCrTeNi2.1-xTiB2 HEA composite coatings with TiB2 addition were improved, and the wear rate of AlCoCrTeNi2.1- xTiB2 HEA composite coatings showed a decreased tendency with the increase of x. However, the wear mechanism of HEA composite coatings are the same, mainly oxidation wear, adhesive wear and fatigue wear.

Study on tribological properties of high entropy alloy composite coatings with different tungsten carbide contents in laser cladding

AbstractThe severe working conditions of mining machinery make the wear of its parts extremely serious, thus reducing its service life, increasing the probability of accidents, and may cause huge economic wastage. So promoting the improvement of mining machinery is imperative, and the melting of wear‐resistant layer on the surface of wear‐prone equipment is a more effective improvement method. The study was performed by laser fusing a composite coating of CoCrFeNiMn high‐entropy alloy with different WC contents, and a second phase was generated in the coating by an additive method to achieve the strengthening of the coating. The experiments revealed that all the coatings had FCC phase as the main phase by analyzing the phase conformation, structure, stiffness, and abrasiveness. When the WC dosage exceeded 20 wt.%, Fe3W3 (M6C) carbide reinforced phases with different morphologies were produced in the coatings. Forty wt.% of the coatings showed the highest hardness, which was 3.1 times better than that of the coatings without WC particles, and 30 wt.% of the coatings showed the best abrasiveness. HT0 coatings showed the least friction factor of 0.27. HT600 and HT800 corresponded to friction factors of 0.37 and 0.35, respectively. The coefficient of friction of the coating was most stable after about 3 min at room temperature, and the wear phase took longer after annealing. During the break‐in phase, the precipitated phase has a supportive effect and prolongs the break‐in period. The coating using the studied method improves the wear resistance of mechanical parts and extends their service life, which has some economic and practical value.

Correction: Tong et al. Effect of Micro-Textures on the Surface Interaction of WC+Co Alloy Composite Coatings. Coatings 2022, 12, 1242

Affiliation Correction [...]