Behaviour of Co binder phase during diamond deposition on WCCo substrate

Park, B.S.; Baik, Young‐Joon; Lee, K.-R.; Eun, Kwang Yong; Kim, D.H.

doi:10.1016/0925-9635(93)90249-2

Cited by 59 publications

(7 citation statements)

References 5 publications

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“…Moreover, the surface concentration of the binder, as measured by Auger electron spectroscopy, decreased below the bulk value at deposition temperatures >900°C. In contrast, Park et al 12 found that a cobalt-rich spongy phase started to segregate at the substrate surface after 15 min of deposition at 950°C. Therefore, given the experimental results of the two research groups, the binder behavior during the early stages of film formation at relatively high temperatures still is not fully understood.…”

Section: Introductionmentioning

confidence: 89%

Early Stages of Diamond‐Film Formation on Cobalt‐Cemented Tungsten Carbide

Polini

Normand

Marcheselli

et al. 1999

Journal of the American Ceramic Society

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The surface composition of cemented tungsten carbide (WC-5.8 wt% Co) was studied by X-ray photoelectron spectroscopy (XPS), during the early stages of diamondfilm deposition, by hot-filament chemical vapor deposition (HFCVD). The nucleated diamond films were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and automatic image analysis (AIA). The evolution of the surface composition of cemented tungsten carbide during the early stages of diamond-film deposition was strongly dependent on the substrate temperature. At relatively low temperature (750°C), cobalt-rich particles started to segregate at the substrate surface after a few minutes of diamond deposition. The conspicuous segregation of the binder partly inhibited the formation of stable diamond nuclei, through intense carbon dissolution or carbon segregation at the binder surface, but did not affect nucleic growth. At higher temperatures (940°C), no cobalt-rich particles formed at the substrate surface, even after 2 h of deposition. However, XPS results demonstrated the presence of cobalt in a surface layer, although in a lower amount than at 750°C. Nevertheless, the nucleation density of diamond at 940°C was much lower than at 750°C. Gaps between WC grains formed within 10 mins. Therefore, intergranular cobalt was removed at 940°C, a finding attributed to the etching performed by monohydrogen, rather than to binder evaporation. The time evolution of the substrate area fraction covered by diamond islands, S(t), was well described by Avrami kinetics for twodimensional phase transformations, suggesting that diamond formation took place via a heterogeneous nucleation process. The S(t) functions exhibited a similar trend at 750°a nd 940°C, because the higher growth rate of diamond crystallites at higher temperature counteracted the slower nucleation rate at the higher temperature.

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Section: Introductionmentioning

confidence: 89%

Early Stages of Diamond‐Film Formation on Cobalt‐Cemented Tungsten Carbide

Polini

Normand

Marcheselli

et al. 1999

Journal of the American Ceramic Society

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“…This observation has been frequently reported by other workers. [25][26][27] Despite the Co fraction volume, with both types of substrates being the same the coarse-grain substrate showed greater density of such drops. Because the temperature of the coatings is below the liquid phase formation during cemented carbide sintering, it is expected that the drop formation (Fig.…”

Section: Cobalt Diffusionmentioning

confidence: 96%

Cobalt diffusion in different microstructured WC-Co substrates during diamond chemical vapor deposition

Cabral

Ali

Titus

et al. 2005

J Phs Eqil and Diff

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Our investigation on diamond deposition using cemented tungsten carbide (WC-Co) has shown that diamond particles deposit at different rates onto micrograin and coarse-grain WC-Co substrates. Diamond deposition was carried out using a parallel-plate plasma-enhanced chemical vapor deposition system, which utilized the bias-enhanced growth (BEG) process. BEG was performed at four different times: 15, 20, 25, and 30 min. The resultant diamond-based deposits were characterized for morphology, microstructure, and crystallinity using scanning electron microscopy. It was found that diamond nucleation initiated at the grain boundaries of the substrates. The present article discusses the possible reasons that can potentially explain our key findings. In particular, the CO diffusion from the bulk material through the grain boundaries and onto the substrate surface using a theoretical approach.

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“…They include removing Co from the substrate by selective acid [5][6][7][8][9] or basic [10] etching, decarburising [6, 11,12] the substrate prior to deposition, introducing intermediate layers *contacting author: fax +39 6 90672-238, E-mail: emilc@mlib.cnr.it [7,9,[13][14][15][16][17]. All these methods resulted to be effective in some way, but no definite and conclusive results have been achieved.…”

Section: Introductionmentioning

confidence: 97%

Pulsed Laser Treatment of WC, Co Tool Substrates to Improve Co Removing and Diamond Nucleation

Cappelli¹,

Orlando²,

Pinzari³

et al. 1998

MRS Proc.

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Diamond coated cutting tools seem to be one of the most promising system to machine non ferrous, very hard materials, like metal matrix composites (MMC), carbon fibers, hypereutectic Al/Si alloys. The widespread used and cheaper bulk material for tool inserts, the WC,xCo hard metal, is convenient and profitable as a substrate for diamond film coatings. Unfortunately, the Co-rich binder phase constitutes a severe obstacle for diamond deposition. Because of the catalytic effect for amorphous carbon or soot formation, the presence of Co actually results in a detrimental effect both on diamond nucleation and adhesion to substrate. Several chemical and physical methods have been developed to etch Co from the surface, no conclusive and perfectly reliable procedure, however, has been achieved, as far as a strong adhesion is concerned.In our experiments, we used ArF (. = 193 nm, hv = 6.4 eV) and Nd:YAG (?= 532 nm, hv 2.3 eV) pulsed laser treatment to selectively remove Co from the surface and to seal the structural voids, coming out after Co chemical etching from the substrate, and responsible of surface segregation of Co from the bulk, during CVD diamond deposition. The sealing efficiency, after a thermal treament (3h, 800 'C) in an inert atmosphere, resulted to be quite good, compared to the untrated surface. The morphological and chemical effects have been studied by SEM/EDAX microscopy.

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Behaviour of Co binder phase during diamond deposition on WCCo substrate

Cited by 59 publications

References 5 publications

Early Stages of Diamond‐Film Formation on Cobalt‐Cemented Tungsten Carbide

Early Stages of Diamond‐Film Formation on Cobalt‐Cemented Tungsten Carbide

Cobalt diffusion in different microstructured WC-Co substrates during diamond chemical vapor deposition

Pulsed Laser Treatment of WC, Co Tool Substrates to Improve Co Removing and Diamond Nucleation

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