WC-Co Particles Research Articles

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.

SLURRY EROSION PERFORMANCE OF COLD SPRAYED WC-12Co COMPOSITE COATINGS

In the current investigation, a cold sprayed WC-12Co (WC- Tungsten Carbide, Co- Cobalt) composite coating was deposited on CA6NM steel. Further, microstructural analysis was carried out by using Scanning Electron Microscopy (SEM)/Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) characterization techniques. Mechanical characterization was carried out to measure microhardness, bond strength and surface roughness. The value of coating hardness and surface roughness was measured to be 270 ± 15 Hv and 2.12 ± 0.5 [Formula: see text]m. Thereafter, slurry erosion test was performed under accelerated conditions and performance of coated samples was compared under different parameters such as erodent size, impact velocity, angle of impingement and slurry concentration. WC-12Co coatings show no phase transformation or de-carburization of the WC-Co particles as observed in other thermal spray techniques. The WC-12Co coatings was proved to have beneficial erosion reduction rate as compared to untreated CA6NM steel. The slurry erosion performance of coated samples was improved by 68%. SEM images of degraded coatings show the brittle characteristic of WC-12Co coatings.

Effect of Local Remelting and Recycled WC-Co Composite Reinforcement Size on Abrasive and Erosive Wear of Manual Arc Welded Hardfacings

The hardfacings reinforced by recycled (cermet inserts of machining tools) WC-Co composite particles applied by manual arc welding can be used for protection against abrasive and erosive wear. Two categories of coatings were analyzed: with and without thermal treatment (local remelting). The hardfacings were tested under abrasive (low and medium stress) and erosive (high stress) conditions. In elevated temperature erosive conditions, coatings without heat treatment have up to two times higher wear resistance than reference material. Under low-stress conditions, coatings with the finest reinforcing particle size (180–355 µm) treated with local remelting demonstrated more than 10 times higher wear resistance than reference material. The optimal reinforcement size selection depends on the application conditions (low, average, or high stress). In most test conditions, the local remelting did not provide additional improvement. A scanning electron microscope was used for the characterization of wear mechanisms. The relation between mechanical properties and wear rates was found only for some conditions.

Preparation of spherical WC-Co powder by spray granulation combined with radio frequency induction plasma spheroidization

In this paper, spray granulation and radio frequency plasma spheroidization were used to obtain spherical WC-Co powder for laser powder bed fusion from mixed WC and Co powder. The effects of solid content and polyvinyl alcohol content of the slurry on granulated powder were studied. Then the spheroidization effects of different granulated WC-Co powders were investigated and compared. Results show that the granulated powder obtained from the slurry with solid content of 65 wt% and polyvinyl alcohol content of 2.5 wt% has the best performance after plasma spheroidization, whose flowability and apparent density are 10.20 s/50g and 6.76 g/cm3, respectively. Moreover, W and C distribute uniformly in the spheroidized WC-Co powder while the Co element is mainly distributed in the gaps of tungsten carbide. It is also noted that W2C, free carbon and Co3W3C appear in the spheroidized WC-Co powders due to the decomposition of WC during the plasma spheroidization process. Furthermore, the decomposition of WC-Co powder particles with smaller size is more serious, which leads to the presence of black and white particles with significantly different carbon content distribution in the spheroidized powder.

High wear resistance WC-Co reinforced GCr15 bearing steel composite prepared via selective laser melting (SLM)

Among numerous reinforced particulates, WC-Co particles are regarded as a promising reinforcement for Fe matrix composites to enhance the tribological properties. Because of the particles’ high chemical stability, and high hardness. In this study, WC-Co particles were chosen as reinforcements to produce GCr15 bearing steel matrix composites by SLM. The microstructures and friction performance of the composites were observed and analyzed. The effect of the laser line energy density (LED) on phases, microstructure and friction performance features is investigated systematically. The phase of samples added with WC-Co particles changed obviously, from mainly α-Fe to γ-Fe. At the same time, Fe7C3, WC, CrSi2, M3W3C phases were found in the composites. The composite prepared by SLM has a good inter-reaction interface between the GCr15 bearing steel matrix and WC-Co particles. Two special microstructures, nail-shaped and cellular microstructure were found in the composites, and with the increase of LED, the size of the cellular microstructure increased, maximum average size is 1.45 μm. After adding WC-Co particles, the properties of GCr15 bearing steel were significantly enhanced, and the microhardness increased from 651 ± 61 HV0.2 to 1093 ± 139 HV0.2, and the COF and wear rate decreased from 0.5091 and 1.82 ± 0.17 × 10−6 mm3N−1 m−1 to 0.4116 and 0.58 ± 0.11 × 10−6 mm3N−1 m−1, respectively

Selective laser melting of WC-Co reinforced AISI 1045 steel composites: microstructure characterization and mechanical properties

Due to the limited wear resistance, AISI 1045 steel has limited applications in harsh environments, and the friction effect leads to premature scrapping. In order to improve the mechanical properties of AISI1045 steel, in this study, WC-Co particles reinforced AISI 1045 steel composites were produced by selective laser melting (SLM), and mainly focused on the influence of laser line energy density (LED) on the microstructure and mechanical properties in detail. The Vickers hardness test and rotational friction test were conducted to determine the Vickers hardness and friction resistance properties of composites. Results demonstrated that the SLM 500 J/m WC-Co/AISI 1045 steel composites possesses higher Vickers hardness and wear resistance compared to that of other samples owing to the finer grains and higher relative density. Herein, the wear mechanism and the binding interface of the SLM composites was also deeply discussed in this paper.

Mechanical Characterization and Tensile Fractography of Al7075-WCP-CoP Composite

The demand for materials with an unusual combination of properties has increased tremendously at a level that cannot be attained through the use of conventional materials. This is especially true for materials used in aircraft, automotive and power generation applications. The microstructure and mechanical properties of Al7075 – 6, 9 and 12 wt.% WC-Co particles reinforced composites are shown in this study. Liquid metallurgy is used to create the composites. The planetary ball milling method is utilized to turn the WC-Co mixtures into cermets, and the particles with a size range of 30-40 µm are employed as reinforcement. SEM and EDS analyses were used to characterise the microstructure. ASTM standards are used to test the mechanical characteristics of both as cast Al7075 and Al7075-6, 9 and 12 wt.% WC-Co composites. SEM was used to perform fractography study on the prepared composite.

Microstructure and wear resistance of bimodal cemented carbide coating prepared by direct laser powder deposition

Compact spherical WC-12Co composite powder was deposited on 304 stainless steel substrate by multi-layer laser powder deposition (LPD) to fabricate cemented carbide coating. The phase constitution and microstructure of the coating as well as the feedstock powder were characterized. Microhardness and dry sliding wear tests were also performed to assess the mechanical properties of the coating. The results showed that the coating exhibited distinct microstructures and phase constitutions at different depths due to the various thermal cycles and the resulting heat damages of feedstock powders. The upper region of the coating (i.e. the wear resistant layer) exhibited bimodal microstructure in which the incompletely dissolved WC-Co composite particles preserved the original submicron sintered structure and secondary carbides were precipitated around them. Owing to the fine-grained strengthening of submicron WC grains in the undissolved areas, the microhardness of wear resistant layer was enhanced to 8 times that of the substrate. The wear rate of the cemented carbide coating was about three orders of magnitude lower than that of the substrate when dry sliding against Al2O3 ball under 10 N normal load. The bimodal structure of the wear resistant layer and the synergistic enhancement of differently sized carbides are the key factors for the excellent wear resistance of the coating.

Core-shell structural iron based metal matrix composite powder for laser cladding

WC is considered as a good choice for the reinforced phase of many composite alloys because of its excellent hardness and good wear resistance. In the past, micro WC particles physically mixed with micro metal particles were also widely used in laser cladding, however, micron WC particles often sink down to the bottom and may cause uneven element distribution, holes, cracks, and other defects in the cladding layer due to its high density and high laser absorption rate. Here, we prepare a core-shell structural 420-nano WC-Co composite powder by high energy ball milling. The composite powder has high circularity and high fluidity, which is suitable for laser cladding. The cladding layer with no holes or cracks can be attained using the core-shell structural composite powders, moreover, the nano WC-Co particles are evenly distributed in the cladding layer and the microhardness of the cladding layer has enhanced significantly.

Ultralow-cobalt hard alloys obtained by spark plasma sintering

The features of spark plasma sintering (SPS) of plasma-chemical nanopowders WC-(0.3, 0.6, 1) wt.% Co were studied. The SPS process of ultralow-cobalt hard alloys can be sequentially represented as a change of the following mechanisms: rearrangement of particles at lower temperatures (Stage I) → sintering of WC-Co particles due to Coble diffusion creep of cobalt, the intensity of which is determined by the grain boundary diffusion rate (Stage II ) → sintering due to diffusion creep, the rate of which is limited by the bulk diffusion in cobalt (Stage III-1) → sintering of tungsten carbide particles along the intergranular boundaries of WC / WC under conditions of intensive grain growth (Stage III-2). Samples with a high density (96.4-98.4%) and high mechanical properties were obtained (for the WC-0.3% Co hard alloy: Hv ∼ 20.5 GPa, KIC = 7.1 MPa · m1/2).

Effects of WC-Co reinforced Ni-based alloy by laser melting deposition: Wear resistance and corrosion resistance* *Project supported by the National Key Research and Development Program of China (Grant No. 2017YFB1103604), the Industrial Transformation and Upgrading Funds of the Ministry of Industry and Information Technology, China (Grant No. RZJC-XM19-004), the Tianjin Municipal Special Program of Talents Development for Excellent Youth Scholars,

WC-Co reinforced C276 alloy composite coatings are fabricated on Q235 steel by laser melting deposition. The microstructure, hardness, wear performance, and electrochemical corrosion behavior of composite coating are studied. The results show that WC-Co particles are mostly uniformly distributed in the coating and provide favorable conditions for heterogeneous nucleation. The microstructure of C276/WC-Co composite coatings is composed of γ-Ni solid solution dendrites and MoNi solid solution eutectics. The WC-Co particles can effectively improve the hardness and wear resistance of C276 alloy. The average hardness of the composite coating containing 10-wt% WC-Co (447 HV0.2) are 1.26 times higher than that of the C276 alloy (356 HV0.2). The wear rate of composite coating containing 10-wt% WC-Co (6.95 × 10−3 mg/m) is just 3.5% of that of C276 coating (196.23 × 10−3 mg/m). However, comparing with Hastelloy C276, the corrosion resistance of C276/WC-Co composite coating decreases.

Wear resistance enhancement of HVOF-sprayed WC-Co coating by complete densification of starting powder

A novel alumina-assisted treatment process was proposed to manufacture fully densified and perfectly spherical WC-Co particles for thermal spraying applications. In as-sprayed coating, the decarburization phenomenon common in previous studies was almost entirely eliminated, and a unique binder structure with nanocrystalline and amorphous Co co-existing was obtained. Owing to the strengthening effects of nanocrystalline Co and WC/Co interfacial bonding, the wear resistance of the new coating was 4 times higher than that of the conventional coating prepared with a porous feedstock. Instead of plastic deformation, interface fracture and micro-cutting that mainly occurred in conventional WC-based coatings, fracture of WC grains and subsequent oxidation dominated wear failure of the new WC-Co coating. The present work opens up new opportunities for the fabrication of dense ceramic-metal composite particles and wear-resistance enhancement of cermet coatings.

Building up WC-Co coatings by cold spray: A finite element simulation

The impact of porous WC-12wt%Co and WC-17wt%Co particles onto homologous, smooth surfaces is simulated through a coupled Eulerian-Lagrangian, three-dimensional finite element model, in order to study the build-up mechanisms of cold sprayed WC-Co coatings.Deformation of hardmetal particles upon impact involves compaction and spreading of a rim, whose bottom face experiences heating, close to or even above the melting point of the matrix, and develops large equivalent plastic strain. The rim therefore adheres strongly to the underlying hardmetal. SEM observations of cold sprayed WC-Co particles deposited onto a smooth hardmetal surface show metallurgic bonding of the heated matrix and mechanical fixation as WC grains from the particle indent and penetrate into the underlying material. Little deformation and heating are instead seen in the middle of the contact surface, where adhesion is limited.Deformation of the particle requires the criterion for ductile failure of the hardmetal to be exceeded. This means the deformed rim is also extensively failed and ejects fragments as it spreads. Increasing the momentum of the particle enhances the spreading of the rim and promotes its bonding to the underlying surface, but also causes ejection of larger fragments, as well as the elastic storage of a greater amount of rebound energy, which can result in eventual rebounding of the entire particle or its poorly bonded central portion. It is therefore inferred that the deposition efficiency of cold sprayed hardmetals cannot increase linearly with impact velocity, and it is further impaired with stiff, dense particles and/or with very hard materials (e.g. WC-12Co as compared to WC-17Co).

Wear resistance of Al2O3/WC-Co/epoxy coatings on TC18 (Ti-5Al-5Mo-5V-1Cr-1Fe) alloy

In this paper, Epoxy/Al2O3 and Epoxy/WC-Co coating were obtained on TC18 titanium alloy by air spraying process. The effect of adding nano filler Al2O3 and WC-Co ceramic particle in the epoxy resin coating on dry sliding at ambient temperature has been investigated. It was found that the addition of Al2O3 and WC-Co particles could improve the hardness of epoxy coating while maintaining the toughness of the substrate, which is one of the reasons for the improvement of wear resistance. The results of wear test showed that the friction coefficients of Epoxy/Al2O3 and Epoxy/WC-Co coating were 0.72–0.73 and 0.62, slightly higher than that of the TC18 alloy substrate. However, the specific wear rates of the Epoxy/Al2O3 and Epoxy/WC-Co coating were greatly reduced and the wear resistance was improved. Compared with the TC18 titanium alloy substrate, the wear resistance of Epoxy/Al2O3 coating increased by 64.7%–69% after adding ceramic particles, which was slightly higher than that of Epoxy/WC-Co coating by 59.4%–62%. The excellent wear resistance of the Epoxy/Al2O3 can be attributed to its high resistance to plastic deformation and nano effect of Al2O3 particles. The wear mechanism of TC18 titanium alloy was mainly abrasive wear, while Epoxy/Al2O3 and Epoxy/WC-Co coatings were adhesive wear.

Numerical and Experimental Investigation on Bonding Behavior of Cold Sprayed Porous WC-17Co Particles onto Different Substrates

Cold sprayed WC-Co metal matrix composite coatings have shown great potential in wear-resistance applications. This work aims to use experimental and numerical methods to clarify the deposition and particle–substrate bonding behavior of a single porous WC-17Co particle onto various substrates. To achieve this objective, porous WC-17Co particles were used as the feedstock; soft Al 2024 (Al alloy) and hard stainless steel 316 (SS) were used as the substrates. The experimental results revealed that brittle WC-Co particles tended to remain intact after depositing on a soft Al alloy substrate, but underwent serious fracture when impacting on a hard SS substrate. Further results indicated that the high energy dissipation and the consequent high stress concentration in the WC-Co particle was the main reason for inducing the particle fracture. In addition, two different mechanical interlocking mechanisms were identified during the WC-Co particle deposition process (namely WC reinforcement interlock and WC-Co particle interlock), dominating the particle-substrate bonding. A soft Al alloy substrate resulted in better interlocking than a hard SS substrate, thereby the corresponding particle bonding ratio was also much higher.

Dissipation of tungsten and environmental release of nanoparticles from tire studs: A Swedish case study

Tire studs, with pins made of cemented tungsten carbide with cobalt (WC-Co), are used in many countries during winter. Tungsten, the main content of the pins, is geochemically scarce and a critical raw material. In addition, analytical studies have identified WC-Co nanoparticles in the environment, which are worn off during the use of studded tires. The aims of this study are to assess (i) the dissipation rate and functional recycling related to the use of tungsten in tire studs as well as (ii) the magnitude of the WC-Co nanoparticle release in Sweden. Tungsten mass flows related to WC-Co in tire studs were estimated throughout the product chain, from mining to waste management, using material flow analysis. This study shows that 100% of the tungsten in Swedish tire studs is presently dissipated (67% as release during use) and there is no functional recycling. This can be compared with the estimated average global dissipation rate of >60% and functional recycling rate of 10–25% after use for tungsten. Recovery of tungsten during waste management and alternative solutions to WC-Co in tire studs are discussed as possible remedies. Furthermore, the estimated release of nano-sized WC-Co particles is in the same order of magnitude as the modeled release of some engineered nanomaterials in Sweden and higher than for e.g. nano-silver.

Corrosion behavior of Al2O3-WER and WC-Co-WER coatings on TC18 in neutral salt spray environment

Al2O3 and WC-Co water-based epoxy resin(WER) coatings for corrosion protection of TC18(with the composition of Ti-5Al-5Mo-5V-1Cr-1Fe) are prepared by air spraying. Two kinds of coating are investigated by scanning electron microscopy and x-ray diffract meter, adhesion evaluation is conducted by grid test. The results show that the coatings are continuous without defects and the level of adhesion up to 4B according to the standard of ASTM D3359. Neutral salt spray test of 750 h is carried out and corrosion resistance is measured by potentiodynamic polarization studies and electrochemical impedance analysis. The corrosion potential and corrosion current density of the WC-Co-WER coating are −0.139 V, 2.520 × 10−8 Acm−2, respectively, and Al2O3-WER coating are −0.195 V, 2.891 × 10−8 Acm−2, respectively. The protective efficiency of the WC-Co-WER coating is 87.6%, which is higher than that of the Al2O3-WER coating with 85.8%. Epoxy resin has good corrosion resistance, the surface of WC-Co-WER coating has more epoxy resin due to sedimentation of the WC-Co particles, WC-Co particles concentrate inside the coating retard infiltration of the corrosive. The above characteristics made the WC-Co-WER coating perform better in corrosion resistance.

Cold spraying of WC-Co-Ni coatings using porous WC-17Co powders: Formation mechanism, microstructure characterization and tribological performance

WC-Co metal matrix composite is frequently applied in the form of coating to prevent the underlying base materials from serious wear. Cold spray has been successfully used to produce WC-Co coatings in recent years, showing great potential. However, due to the lack of sufficient Co matrix phase for plastic deformation, the fabrication of cold sprayed WC-Co coating naturally requires expensive propulsive gas or very high working parameters, significantly increasing the manufacturing difficulty and cost. This paper aims to use conventional high pressure cold spray to fabricate WC-Co-Ni wear-resistance coatings under moderate working parameters, and to clarify the coating formation mechanism. To achieve this objective, mechanically mixed porous WC-17Co and dense Ni powders were selected as the feedstock with different WC mass fractions, F1 (41.5 wt%), F2 (64.5 wt%) and F3 (74.7 wt%). Working parameters were set at a moderate level (nitrogen, 3.0MPa and 350°C). Experimental results show that the WC reinforcements had no phase transformation and were completely retained in the WC-Co-Ni coatings as compared with in the feedstock. Fracture of the porous WC-Co particles during the deposition process was found to be the reason for such high WC retainability, dominating the coating formation mechanism. Tribological performance test shows that the coating hardness, toughness and wear-resistance performance improved as the WC content increased from the F1 to F3 coating. Wear mechanism analysis demonstrates that the F3 coating exhibited a completely different wear mechanism from the F1 and F2 coatings, thus the F3 coating had the best wear-resistance performance.

Effects of tool wear on friction stir welded joints of Ti–6Al–4V alloy

Tool wear behaviour on microstructure and mechanical properties of friction stir welded zones of Ti–6Al–4V alloy was evaluated. SEM examination, EDS analysis and X-ray diffraction results indicated that severe wear of the tool is indicated by the presence of WC-Co particles in the stir zone at rotational speed of 630 rev min−1 and travel speed of 8 mm min−1. Micro-hardness, tensile tests and fractographical examinations also reflected that these particles make the material more brittle and reduce the mechanical strength by 40%. However at travel speed of 22 mm min−1, tool wear is less, hardness distribution is more uniform and enhanced ductility and strength is achieved.

Plastic deformation phenomena during cold spray impact of WC-Co particles onto metal substrates

This paper studies the plastic deformation phenomena in ductile substrates (Al7075 alloy, carbon steel) during cold spray-deposition of WC-Co. Metallographic inspection of etched cross-sections and through-thickness nano-hardness profiling indicate that plastic deformation of the substrate (into which undeformed WC-Co particles penetrate deep) is confined to a shallow area, below which the material appears unaltered.Adiabatic deformation phenomena in the substrate are revealed by finite element modelling of the impact process. Close to the surface, the temperature raises in less than 10 ns, leading to metal jetting, whilst the underlying material, below a depth of few micrometres, is substantially unaffected.