A Raman Study of Diamond Film Growth on Co‐Cemented Tungsten Carbide

Polini, Riccardo; Traversa, Enrico; Marucci, A.; Mattei, Giorgio; Marcheselli, Giancarlo

doi:10.1149/1.1837598

Cited by 11 publications

(4 citation statements)

References 8 publications

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“…The frequency of this peak is about 5 cm Ϫ1 blue shifted with respect to the value of natural diamond (1332.4 cm Ϫ1 at atmospheric pressure and 25ЊC). This implies that a 1.8 Ϯ 0.1 GPa residual compressive stress was present in the deposited diamond, [25][26][27] which did not depend on the substrate temperature and methane concentration. Figure 11 shows the Raman spectra of diamond films grown at 750ЊC (0.5% CH 4 ) on S, SE, and SMP pretreated substrates.…”

Section: Resultsmentioning

confidence: 94%

Nucleation and Adhesion of Diamond Films on Co Cemented Tungsten Carbide

Polini

Santarelli

Traversa

1999

J. Electrochem. Soc.

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The extreme hardness, wear-resistance, high thermal conductivity, and low friction coefficient of diamond films, combined with the ductility and toughness of Co cemented tungsten carbide (WC-Co) allow the development of coated tools and components with new characteristics. The typical domain of diamond-coated WC-Co tools should include application to the machining of materials such as metal-matrix composite (MMC) materials, Al-Si alloys, nonferrous metals, wood, fiber-reinforced plastics, and graphite. 1-4 Unfortunately, there are several problems associated with depositing good quality and strongly adherent diamond coatings onto WC-Co based components. In fact, the presence at the interface of cobalt hinders the heterogeneous nucleation of diamond. 5-8 In addition, cobalt induces the formation of a nondiamond type of carbon layer at the substrate surface during the early stages of deposition, on which weakly adherent diamond grows later. 9,10 These problems can be reduced by modifications of the WC-Co substrate surface prior to diamond deposition. The various pretreatments reported in the literature include the removal of cobalt by chemical etching, 11,12 the surface decarburization after the etching of the binder, 13 and the deposition of interlayers which act as diffusion barriers for carbon. 14 Moreover, the increase of the interface contact area by roughening the substrate surface has also been proposed as a key factor for achieving satisfactory adhesion, 3,15,16 Besides substrate pretreatments, deposition conditions might influence the mechanical and cutting properties of diamond-coated WC-Co tools. Haubner and Lux 17 found that diamond films deposited at relatively low temperatures (760 Ϯ 10ЊC) by hot filament chemical vapor deposition (HFCVD) showed improved adhesion onto hard metal substrates. Taher et al. 18,19 recently performed an extensive investigation on the effect of methane concentration in the gas phase on the mechanical properties of cutting inserts deposited at 850ЊC by HFCVD.The focus of this work is to examine the combined effects of substrate pretreatments, deposition temperature, and methane concentration on diamond nucleation and film adhesion, in order to determine which are the factors that mainly contribute to the achievement of a good film/substrate interface toughness.Experimental 10 ϫ 10 ϫ 3 mm WC-5.8 wt % Co substrates were sintered using WC with an average grain size of 6 m, which is larger than the grain size (1-2 m) conventionally used to improve the hardness of commercial tools. The substrates were provided by FILMS SpA. The as-sintered samples were ground and then rinsed with acetone and ethanol in an ultrasonic bath. In order to enhance diamond nucleation, to suppress the deleterious effects of the binder, and to increase the contact area at the interface, the substrates were submitted to surface modifications using the mechanical and chemical pretreatments listed and labeled in Table I. Following each pretreatment, the substrates were washed with acetone and deionized water ...

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Section: Resultsmentioning

confidence: 94%

Nucleation and Adhesion of Diamond Films on Co Cemented Tungsten Carbide

Polini

Santarelli

Traversa

1999

J. Electrochem. Soc.

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“…The existence of these modes was ascribed to the formation of transpolyacetylene (TPA) chain in the grain boundaries, which is a familiar characteristic of NCD coatings. A cauliflower type of growth is generally seen with the NCD coatings [36][37][38][39]. As for boron-doped diamond films, 1332 cm -1 peak changes towards an asymmetric Fano effect.…”

Section: Raman Spectroscopy and Residual Stress Analysismentioning

confidence: 90%

Tribological Performance of Titanium Alloy Ti–6Al–4V via CVD–diamond Coatings

Din

Shah

Sheikh

2018

J. Superhard Mater.

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In the present study, HFCVD nanocrystalline, microcrystalline and boron-doped nanocrystalline diamond coatings have been deposited on titanium alloy. The effect of boron doping on coefficient of friction and residual stresses of diamond coatings have been studied. The tribological characteristics of the aforementioned three coatings on Ti-6Al-4V substrates were studied using ball on disc microtribometer, the thickness of the coatings being 3 μm. The coated Ti-6Al-4V discs were slid against alumina (Al 2 O 3 ) balls with normal load ranging from 1 to 10 N. The borondoped NCD coated sample disc was found to possess the lowest average coefficient of friction ~ 0.0804 while the undoped NCD and MCD coated sample discs were found to possess the average coefficients of friction of ~ 0.143 and ~ 0.283, respectively. Raman spectroscopy studies revealed that the residual stresses in boron-doped nanocrystalline coatings were tensile in nature, while the residual stresses in undoped NCD and MCD were found to be of compressive nature.

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“…The gas composition and flow rate were regulated by digital mass flow controllers (Model 258/259, coupled with Model 247A control unit, MKS Instruments, Andover, MA). The substrate temperatures investigated (750°and 940°C) were selected based on the results of a previous study; 13 the deposition temperatures used allowed the growth of high-purity diamond coatings under the present experimental conditions. The deposition times were varied between 10 and 180 min, to allow study of the kinetics of the surface evolution of the substrate during the early stages of the process.…”

Section: (2) Diamond Depositionmentioning

confidence: 99%

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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A Raman Study of Diamond Film Growth on Co‐Cemented Tungsten Carbide

Cited by 11 publications

References 8 publications

Nucleation and Adhesion of Diamond Films on Co Cemented Tungsten Carbide

Nucleation and Adhesion of Diamond Films on Co Cemented Tungsten Carbide

Tribological Performance of Titanium Alloy Ti–6Al–4V via CVD–diamond Coatings

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

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