Magnesium alloys have found widespread application in various industries, mainly due to the combination of low density, the best structural material known today, and high strength to weight ratio. ...However, the use of magnesium alloys is limited due to their poor wear and corrosion behavior. In this study, two commercial powders, agglomerated and sintered WC-Co and WC-Cr3C2-Ni were thermally sprayed to deposit coatings onto two magnesium alloy substrates (AZ31 and AZ91) with a combination of two different spraying distances (320 and 400 mm). The main aim of this work was to investigate the microstructure and corrosion resistance of the coatings deposited by High Velocity Oxy Fuel (HVOF) spraying. The morphology and microstructure of the sprayed coatings were analyzed by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). Additionally, porosity, microhardness and surface roughness were examined. Furthermore, potentiodynamic polarization was used to characterize the corrosion behavior of the deposited coatings. The experimental results showed that manufactured coatings are characterized by a dense microstructure with porosity typical for coatings sprayed with the HVOF method. Moreover small cracks and unmelted carbide particles embedded in the metal matrix were found in the as-sprayed coatings. Based on the results of the potentiodynamic studies it was found that the corrosion resistance of AZ31 and AZ91 magnesium alloys is not very high in a sodium chloride solution. The polarization resistance of AZ31 is very low (241.3 Ω∙cm2) and the corrosion current density is high (57.4 μA∙cm−2), whereas for AZ91 these values are 17.8 Ω∙cm2 and 1612.1 μA∙cm−2, respectively. The corrosion potential of the AZ31 and AZ91 alloy equal −1.56 V which is characteristic for magnesium alloys in a NaCl solution. For both type of substrates, better corrosion resistance has been obtained for the WC-Co coating. The Rp value was nearly 150 times higher than the one for uncoated AZ91 alloy, whereas for AZ31 the polarization resistance was about 17 times higher (Rp = 4.2 kΩ∙cm2) in comparison to non-covered alloy. In summary, all deposited coatings improved the corrosion resistance of the magnesium alloy. However, the WC-Co one protects the magnesium substrate against corrosion more effectively than the WC-Cr3C2-Ni.
•Spray distance and feedstock material affected on coatings porosity value.•Spray distance affected on normal stress values, whereas the type of substrate material affected on shear stress values.•For AZ91 substrate the spray distance did not affected on shear stress values.•Type of feedstock material affected on corrosion resistance.•The influence of spray distance on corrosion resistance was inconsiderable.
In this work, four different vacuum sintering temperatures (1250 °C, 1300 °C, 1350 °C and 1400 °C) were studied to determine the optimal process parameters of nano WC–15 wt% (Fe–Ni–Co) and WC–15 wt% ...Co sintered hard metal alloys. Experimental results showed that the optimal sintering temperatures for nano WC–(Fe–Ni–Co) and WC–Co alloys were 1300 °C and 1350 °C for 1 h, respectively. The sintered nano WC–(Fe–Ni–Co) and WC–Co hard metal alloys showed a good contiguity of 0.44 and 0.42; hardness was enhanced to HRA 90.83 and 90.92; the transverse rupture strength (TRS) increased to 2567.97 and 2860.08 MPa; and KIC was 16.23 and 12.33 MPa√m, respectively. Although the nano WC–(Fe–Ni–Co) alloys possessed a slightly lower TRS value, they exhibited superior fracture toughness (KIC) and hardness similar to that of the nano WC–Co material. Significantly, nano WC–(Fe–Ni–Co) alloys could be sintered at a lower temperature and still retained their excellent mechanical properties.
The following figure shows the fracture morphology of the WC–(Fe–Ni–Co) and WC–Co specimens by means of high-magnification SEM after the KIC tests. Fig. a shows that numerous binder phases (Fe–Ni–Co) existed in the crack areas, which resisted the penetration and extension of the cracks. Due to the bridging effect of the binder phase, the stress concentration of the crack tip will be resolved through plastic deformation; thus, the cracks did not continue to extend. Once the deformation reaches a critical value, the crack propagation occurs. Meanwhile, the binder phase can link together the two crack faces through the bridging process. Although parts of the cracked areas also showed the bridging effect in the WC–Co specimens, as shown by the arrows (Fig. b), the crack propagation path was not obviously affected. This result corresponds to the tortuosity phenomenon. Consequently, the bridging process suppressed the crack propagation and resulted in the increase in tortuosity. SEM observations of the bridging role of the (a) 1300 °C sintered WC–(Fe–Ni–Co), and (b) 1350 °C sintered WC–Co hard metal alloys after KIC tests. Display omitted
•The sintered nano WC–Co alloy sintered at 1350 °C had the highest hardness (HRA 90.92).•The sintered nano WC–(Fe–Ni–Co) alloys showed a good contiguity of 0.44.•The optimal nano WC–Co sintered alloy possessed the highest TRS value (2860.08 MPa).•WC–(Fe–Ni–Co) sintered alloy possessed the highest fracture toughness of KIC (16.23 MPam1/2).•The adding of an iron–nickel instead of a cobalt binder for tungsten carbides is preferable.
•WC–Ni–Fe alloy sintered at 1400°C had the highest hardness (HRA 85.3±0.5).•The optimal WC–Ni–Fe sintered alloy possessed the highest TRS value (2524.5±1.0MPa).•The fracture toughness of the sintered ...WC–Ni–Fe alloys is mainly provided by the Ni–Fe binders.•WC–Ni–Fe sintered alloy possessed the highest fracture toughness of KIC (15.1MPam1/2).•The WC–Ni–Fe sintered alloy had the much better corrosion resistance in 0.15M HCl solution.
The aim of this study is to explore two different tungsten carbide binders (Co and Ni–Fe) and then impose various sintering temperature treatments. Experimental results show that the optimal sintering temperatures for WC–Co and WC–Ni–Fe hard metal alloys are 1350°C and 1400°C for 1h, respectively. Meanwhile, the WC–Co and WC–Ni–Fe alloys undergo a well liquid-phase sintering and, thus, exhibit excellent mechanical properties. In addition, the sintered WC–Co and WC–Ni–Fe alloys show that when the relative density reached 99.76% and 99.68%, the hardness was enhanced to HRA 84.4±0.5 and 85.3±0.5, and the TRS increased to 2471.2±1.0 and 2524.5±1.0MPa, respectively. Moreover, the corrosion test results show that the WC–Ni–Fe alloy sintered at 1400°C had the lowest corrosion current (Icorr) of 1.11×10−5Acm−2 and the highest polarization resistance (Rp) of 2464.61Ωcm2 in 0.15M HCl solution. Simultaneously, the fracture toughness of KIC increased to 15.1MPam1/2. Compared with sintered WC–Co alloys, the sintered WC–Ni–Fe hard metal alloys possessed much better corrosion resistance and mechanical properties.
A nickel–tungsten carbide (Ni–WC) composite is an ideal protective coating for a harsh environment. In this study, the corrosion and wear behavior of a laser cladded Ni–WC coating fabricated by a ...high power direct diode laser (HPDDL) with different chemical compositions was investigated. In the modified Ni–60%WC, the chemical compositions were enhanced by the addition of lanthanum oxide (La2O3) and molybdenum and by replacing a portion of micro-sized WC with nano-WC particles. The corrosive resistance of the coatings was investigated utilizing potentiodynamic polarization, long-term immersion tests, and surface analytical techniques. The corresponding wear response was studied by using a dry unidirectional sliding wear test according to the ASTM G99 standard. Modification of the laser-cladded coatings was interpreted on the basis of its microstructure, microhardness, and phases of chemical composition. It has been observed that an optimal addition of nano-WC (5wt.%), La2O3 (1wt.%), and Mo (1wt.%) refines the grain size of the Ni binder and improves hardness, passivation capability of the coating under corrosion, and wear resistance. The pitting corrosive resistance of the modified coatings was enhanced due to a higher chemical stability, a more uniform surface potential, and a higher passivation capability.
•Corrosion and wear behavior of laser cladded Ni-WC coating was studied.•The coating resistance enhanced by an optimal addition of La2O3, nano-WC, and Mo.•The microstructure, microhardness, and coating chemical composition were modified.•Chemical stability and passivation capability were improved in modified coatings.
Ni-WC composites were prepared by vacuum-induction melting (VIM). A ball-on-disc wear test was performed using an Si3N4 ball as a friction pair to study the wear performance of the composites. The ...effects of WC particle size (average particle size of 68 μm and 23 μm) on the mechanical properties of the composites and the heat-damage behaviour of WC particles during the melting process were investigated. The results indicate that the wear rate of Ni-WC composites with coarse WC particles was lower than that of Ni-WC composites with fine WC particles. The predominant wear mechanism of composites with coarse WC particles was mechanical wear of the WC particles; the predominant wear mechanisms of composites with fine WC particles were oxidation wear and three-body abrasive wear. The coarse WC particles provide better wear resistance than fine WC particles. The WC particles underwent heat erosion and dissolution caused by the Ni-based melt. Increasing the size of the WC particles can significantly reduce the degree of heat damage to the WC particles and improve the hardness of the composites.
•Finer WC particles broken and coarser WC particles less destroyed.•Oxidation wear and three-body abrasive wear for composites with finer WC particles.•Heat damage behaviour of WC particles during melting process.
WC-Co coatings have been extensively used in the applications requiring high abrasion and erosion resistance. However, they are not known to have significant corrosion resistance. In this regard, ...WC-(W,Cr)2C-Ni is a possible candidate material to replace WC-Co for applications requiring a combination of superior tribological and corrosion performance. In the present study, WC-(W,Cr)2C-Ni coatings are deposited on mild steel (MS) substrates using Detonation Spray Coating (DSC) technique and compared with the properties of WC-12Co coatings. The microstructure and phases present in the feedstock as well as coatings are analyzed. The major part of matrix phase is (W,Cr)2C phase in WC-(W,Cr)2C-Ni feedstock and coatings with traces of Ni-Cr phases. High speed nanoindentation testing was used to map the hardness of the feedstock and coatings. The average hardness value of (W,Cr)2C phase is found to be around 15GPa with a range from 12 to 20GPa. Three body abrasive wear and corrosion properties of the coatings were evaluated and correlated with the corresponding microstructure and mechanical properties. While the wear resistance of WC-(W,Cr)2C-Ni coating is marginally better than WC-12Co coatings with the presence of (W,Cr)2C hard phase as a matrix phase and the presence of Ni and Cr and its associated phases in WC-(W,Cr)2C-Ni coatings are responsible for exhibiting nobler corrosion potential and significantly reduced corrosion current densities therefore confers superior corrosion resistance compared to WC-12Co coatings.
•The average hardness of (W,Cr)2C matrix phase is 15GPa in WC-(W,Cr)2C-Ni.•WC-(W,Cr)2C-Ni coatings exhibited marginally better abrasive wear resistance.•The presence of two hard phases WC and (W,Cr)2C resulted less abrasive wear loss.•Eight times better corrosion resistance in WC-(W,Cr)2C-Ni coating than WC-Co coating•Higher charge transfer and lower oxide resistance noticed in WC-(W,Cr)2C-Ni coating
This paper described the difference of tribological behaviors and wear mechanism between WC-10wt%Co and WC-10wt%Fe3Al. By spark plasma sintering (SPS) method, the two materials were successfully ...fabricated under lower sintering temperature (1150°C). Friction and sliding wear tests were carried out under dry conditions. The results showed that Hardness and wear resistance of WC-10wt%Fe3Al is much higher than WC-10wt%Co. The spectrums of Raman laser scattering showed WC-Fe3Al posses good oxidation resistance. Energy dispersive spectrums (EDS) verify the existence of Al2O3 in WC-10wt%Fe3Al and this is the important factor that leads to the better wear and oxidation resistance of WC-10wt%Fe3Al.
•The tribological behavior and wear mechanism of WC-Co and WC-Fe3Al are investigated in this paper.•WC-10wt%Fe3Al showed much lower wear rate and less value changes than WC-10wt%Co. Moreover, the wear rate of the two materials become similar and the lowest when the sliding velocity is 0.12 m/s.•WC-10wt%Fe3Al possesses better wear and oxidation resistance properties than WC-10wt%Co partly owning to the formation of Al2O3 in WC-10wt%Fe3Al.
Corrosion behavior and scratch performance of Al-WC nanocomposites with varying wt% of WC are evaluated in this study. Liquid metallurgy-based stir-casting route is used for fabrication of the ...nanocomposites. Particles are distributed in the matrix as confirmed by EDAX (energy-dispersive X-ray) spectrum and XRD ( X-ray diffraction) analysis. The micro-hardness of nanocomposites increases with the increase of wt% of WC particles. Corrosion behavior is studied under different corrosive environments, viz., neutral, alkaline and acidic solution. Tafel plots and Nyquist plots are obtained under the neutral medium (3.5 wt% NaCl aqueous solution), while only Tafel plots are obtained under 0.5 M NaOH solution and 0.5 M HCl solution. Among all three operating mediums, NaCl solution is the least corrosive for the composite. Corrosion rates under NaOH and HCl medium are high and values are very close to each other. The least amount of reinforcement, 0.5 wt% of WC, yields the best corrosion resistance under the neutral solution. The corrosion resistance increases with the amount of reinforcement under alkaline and acidic mediums. From SEM (scanning electron microscope) images of the corroded surfaces, pitting corrosion is observed for Al-0.5%WC composite while exfoliation with deeper cracks is observed for composites with a higher amount of WC. Scratch performance is also evaluated for a load range of 5 N to 20 N. Scratch resistance increases with increase in wt% of nano-particles. Surfaces after scratching are characterized using optical microscope, SEM, and EDAX spectrum.
•Al-WC nanocomposites are synthesized through ultrasonic assisted stir casting method.•Corrosion behavior is investigated in three different corrosive mediums.•Scratch characteristics are obtained for varying loads.•Worn surface morphology is examined to ascertain the possible wear mechanisms.
This research focuses on studying the powder reactions and coating microstructures produced by thermal spraying various particle sized (micro and nano-sized) tungsten carbide cobalt powder. High ...Velocity Oxy Fuel (HVOF) and Atmospheric Plasma thermal spray methods were used to perform a multi-layer coating applied onto carbon steel specimens (typical of those used in oil/gas industry). The thermally sprayed powders/coatings were analyzed using X-ray powder diffraction (XRD), Environmental scanning electron microscope (ESEM), and Energy Dispersive Spectrometry (EDS) to predict the metallic powder reactions. In addition, surface roughness measurement of the coating, hardness assessment, and evaluation of coating porosity and adhesion were conducted to determine the coating characterization. The comparative metallographic results of the various test coatings are discussed. Results show that higher phase transformation occurred in the plasma thermal spray and more cobalt evaporation occurred during the deposition of the nano-sized powder. The plasma spray of nano-sized powders yielded lower coating roughness (from 5.5μm to 4.6μm), whereas it increased the roughness when sprayed with the HVOF system (from 3.1μm to 4.3μm). Nano-sized powders improved porosity but not significantly (to 1.2%). However, the higher percentage of nano-sized particles in the starting powder increased the hardness in the coatings to 1367HV. Among the four produced coatings, the results concluded that the coating produced by HVOF using nanostructured WC–12Co powder was found to have the best coating microstructure due to its low porosity, high density, good adhesion, and fracture resistance.
•HVOF and Atmospheric Plasma thermal spray methods were used to perform a multi-layer coating applied onto carbon steel specimens.•Micro and nano-sized WC-12Co powder reactions and coating microstructures were studied.•Coating produced by HVOF using nano structured powder performed well in wear and corrosion applications.
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•WO3/WC hybrid is designed and synthesized by facile annealing method.•WO3/WC hybrid with low Zn2+ intercalated potential is demonstrated.•The strong interaction and electronic ...coupling between WO3 and WC are determined.•Significant rate and cycling stability can be achieved for WO3/WC hybrid.•The WO3/WC||MnO2/graphite rocking‐chair ZIBs achieve excellent performance.
Aqueous Zinc-ion batteries (ZIBs) are recognized as the most pivotal competitor of lithium-ion batteries due to their abundant reserves, remarkable safety and affordable cost. However, the uncontrollable dendritic growth and extremely low utilization (<5%) of zinc metal anode severely limit the practicality and energy density of ZIBs. Herein, a novel rocking-chair ZIBs with excellent cycling stability and high energy density is developed via employing tungsten oxide/carbide (WO3/WC) layered heterogeneous hybrid with strong-coupling effect as the intercalated anode and MnO2/graphite cathode. Benefiting from the favorable interface energy and electronic coupling with prominent charge-transfer between WO3 and WC, the WO3/WC//Zn batteries deliver admirable capacity of 164 mAh g−1 under 0.1 A g−1 with suitable Zn2+ intercalated potential of 0.43 V (vs. Zn2+/Zn), long-term cyclability with 90.2% after 1000 cycles under 1 A g−1, and reversible Zn2+ intercalation behavior. Consequently, the assembled WO3/WC||MnO2/graphite rocking-chair ZIBs offer excellent capacity of 69 mAh g−1 at 0.1 A g−1, impressive cyclic stability (100% after 10,000 cycles) and exceptional energy density of 85 Wh kg−1, suppressing most of reported rocking‐chair ZIBs. Therefore, this research provides a novel insight for designing safe and high-efficient ZIBs.
