Effect of powder structure on the structure of thermally sprayed WC-Co coatings

Li, Chang-Jiu; Ohmori, Akira; Harada, Yoshio

doi:10.1007/bf00367900

Cited by 127 publications

(60 citation statements)

References 10 publications

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“…In related phase constitution of the nanostructured materials relative to studies, amorphous areas were reportedly found in HVOF those of the conventional materials. Decarburization of the thermally sprayed conventional WC-Co [6,8,17,31] and nanonanostructured WC-12 pct Co powder can be quite severe structured WC-Co coatings [32,33] and sintered bulk during heating. Figure 11(a) illustrates the weight change nanostructured WC-Co material.…”

Section: Microstructure Of Coatingsmentioning

confidence: 99%

“…In fact, it is well documented that none or only trace amounts of Co are detected D. Coating Characterization in commercial sintered WC-12 pct Co powder by XRD. [6,13,24] It was suggested that the Co binder was primarThe cross section of the coating was examined using a PHILIPS XL 30 FEG SEM. The microhardness was estabily either amorphous or in the form of nanocrystalline Co x W y C z compounds, and hence, the intensity peaks are lished on a Buehler Micromet 2004 Microhardness tester is known to absorb Co seven times more than Mo.…”

Section: Hvof Experimentsmentioning

confidence: 99%

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Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

Ice

Lavernia

et al. 2000

Metall Mater Trans A

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A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.

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Section: Microstructure Of Coatingsmentioning

confidence: 99%

Section: Hvof Experimentsmentioning

confidence: 99%

Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

Ice

Lavernia

et al. 2000

Metall Mater Trans A

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“…5,9,[12][13][14] Moreover, it could be considered that the decomposition of the carbide is limited during spraying.…”

Section: Discussionmentioning

confidence: 99%

“…4) The characteristics of the powder feedstock have a significant influence on the coating microstructures, 5) although coating microstructure is often much different from that of the powder due to rapid cooling and solidification features inherent to thermal spray process. 6) In our previous study, it was found that using large WC particles cladding with 18 mass% cobalt the consequent HVOF coating is primarily composed of the matrix of Co-W-C ternary alloy in an amorphous state.…”

Section: Introductionmentioning

confidence: 99%

Deposition Behaviors of Solid Phases in Liquid-Solid Two-Phase Particles in High Velocity Oxy-Fuel Spraying

Wang

Kusumoto

2006

Mater. Trans.

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Three types of composite coatings were deposited by high velocity oxy-fuel (HVOF) spraying using metal-clad WC-18Co and SiC-50Co cermet powders, and sintered-crushed Al 2 O 3 -75Ni composite powders. Liquid-solid two-phase state of the sprayed particles with two different structures was achieved prior to their impingement on the substrate. The effects of particle structure and HVOF spraying parameters on volume fraction of the solid phase were investigated. The distribution of ceramic particle size inside coatings was also clarified. Scanning electron microscopy was employed to characterize the microstructure of HVOF sprayed cermet coatings. The volume fraction of solid particles and the distribution of particle size in the three types of coatings were estimated using a quantitatively metallographic approach from the microstructure of the coatings. The volume fraction of the solid phase in the coating made from Al 2 O 3 -Ni powders was increased with increase in the fuel gas flow. The maximum volume fraction of the Al 2 O 3 phases reached about 64% of the original powder. On the other hand, the volume fraction of solid phase in the clad cermet coatings was decreased with increasing the fuel gas flow. The volume fraction of the solid phase dropped significantly from 72.2% in the original WC-18Co particle to 8.5% in the coating. The limited retention of the solid phase from spray particle to subsequent coating is due to rebounding off of large solid particle upon impacting.

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“…The bulk mechanical properties and wear resistance of tungsten carbide alloys are strongly affected by composition and microstructural parameters which in turn are controlled by initial particles sizes, volume fraction of tungsten and metal binder, WC/WC contiguity, volume fraction of brittle carbide eta phases, sintering time and temperature, and %porosity [3,6,7].…”

Section: Introduction and Background Informationmentioning

confidence: 99%

Failure Analysis of WC–2Ni–1Co Rotor Part

Faraz

Tariq

Ali

et al. 2010

J Fail. Anal. and Preven.

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This study deals with the analysis of an inkproducing machine rotor part composed of WC-2Ni-1Co which failed in brittle manner during service. The part was made by powder metallurgy techniques and is being used in ink-grinding machines due to its high hardness and wear resistance. Similar parts had worked satisfactorily for many ink compositions, but the part under investigation failed prematurely. Investigation was considered important because the part is expensive, and other identical components frequently failed after a short service life. Moreover, replacement of the part requires complete dismantling of the machine which reduces the production rate. Spectroscopic analysis, density, optical and scanning electron microscopy, SEM-EDS analysis, fractography, X-ray diffraction, and microhardness measurements were carried out on failed parts to find out the root causes of the failure. Results revealed that the part cracked due to combined effects of selective dissolution of metal binder-caused corrosive action of ink solution and hydrogen-induced deterioration of WC and Ni-Co phases. Localized removal of binder phase left the hard WC phase unsupported. Cracks were found initiating from the root of the machined slot which acted as a stress concentration point and resulted in brittle fracture.

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Effect of powder structure on the structure of thermally sprayed WC-Co coatings

Cited by 127 publications

References 10 publications

Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

Deposition Behaviors of Solid Phases in Liquid-Solid Two-Phase Particles in High Velocity Oxy-Fuel Spraying

Failure Analysis of WC–2Ni–1Co Rotor Part

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