Engineered Interfaces for Adherent Diamond Coatings on Large Thermal-Expansion Coefficient Mismatched Substrates

Abstract

logged stand of trees. 21. Lltterial data from (S), ndcate that t t e r f a lnputs of carbon are between about 50 and 120 g m-'year-' for coniferous forests of the Slerra transect above 1200 m eevaton We estimated carbon productivity for grasses at the Fabrook slte by assumng that ther v a l~~e s are smlar to those for other grassland soils In Cafornla (between 50 and 100 g m-' y e a r 1 [R. Vaentn et a1 , Ecology 76 1940 (1 995)] 22 D. C. Nepstad e i a/. , i~laiure 372 666 (I 994) 23 S E Trumbore er a1 , Global Biogeochem Cycles 9. 515 (1995). 24. W M Post era/., Nature 298, 156 (1 982); D. S. Jenklnson, D E Adams, A. W11d /bid 351,304 (1991), A. R. Townsend eta/., Chm Change 22, 293 (1992). 25. M. Klrschba~lm So11 Blol. Biochem. 27, 753 (1 995). 26. The est~mates of carbon change In Fig. 3 Ignore important factors, such as probable changes n carbon inputs to the soil by plants and feedbacks be-tween SOM decomposton and plant productivity, In additlon the climate transects studled ~n H a w a and the Serra Nevada Integrate long-term adj~~stment of ecosystems to average cllmatic cond~t~ons, and translent responses may not be predctabe from the temperature-turnover relations derlved here However, soil incubations and sol respratlon measurements have shown that on short t m e scales, carbon fluxes from soils are strongly dependent on temperature, with Ql , values ranglng from 2 to 5 [J. W. Rach and W. H. Schesnger, Tellus 448, 81 (1 992); D W. Klckghter er a/., J. Geophys Res. 99, 1303 (1 994)] (25) In accord with values, derlved from F g 2, of 3 0 to 3 8. [Q,, 1s the rateoia b i o o g c a process (here, decompositon) at one temperatwe divded by the rate of the process at a temperature 10°C cooler ] 27.

Hot filament chemical vapour deposition and wear resistance of diamond films on WC-Co substrates coated using PVD-arc deposition technique

“…The overall results indicate that chemical bonds between diamond and TiN were not strong enough, and that the satisfactory adhesion level in the case of the TiN _ a sample was mainly caused by PVD rough surface. According to Singh et al [15] this might increase the adhesive strength of the film by modifying the stress distribution in the diamond coating. On the contrary, rather than being caused by the interface morphology, diamond deposited on CrC PVD film showed good adhesion due to stronger chemical bonds between diamond film and chromium carbides (Fig.…”

Co removal and phase transformations during high power diode laser irradiation of cemented carbide

“…A comparison between the evolution of the WC-Co morphology after diode and pulsed laser processing can be performed [44][45][46]. There are significant differences in the setting of the operational parameters of the two techniques, which complicate the comparison.…”

“…In addition, interlayers can be designed to adjust the thermal expansion coefficients between WC-Co and diamond, thus reducing thermal residual stresses inside the diamond coating during CVD [35][36]; (iii) mechanical treatments, in which mechanical interlocking between diamond and WC-Co is promoted by micro-or macrocorrugating WC-Co or the interlayer surface [36][37][38]. These mechanical treatments mostly follow [44][45][46]. Nonetheless, the pulsed diode laser source was operated at a very high laser irradiance (> 80 MW/cm 2 ).…”

“…In addition, some Co and W oxides could be easily generated at such a high processing temperature, if precautions to protect the WC-Co substrates from oxygen were not taken [46]. These results necessitated the combination of the pulsed laser source with further chemical treatments like etching with dilute acid solutions to remove the excess in Co and, eventually, most of the oxides, thus reducing the potentiality, safety and industrial suitability of the technique [44,46].…”

On the use of CrN/Cr and CrN interlayers in hot filament chemical vapour deposition (HF-CVD) of diamond films onto WC-Co substrates

“…Several procedures can be distinguished whereby the untreated WC-Co substrates material can be improved: i) the removal of the Co-binder phase from the substrate surface with aqueous solutions of either strong oxy-acids or hydrochloric acid [8][9][10][11][12][13][14][15]; ii) the use of interlayer materials as carbon and cobalt diffusion barrier to suppress interactions of Co with the hydrocarbon radicals rich gas phase in the CVD atmosphere during deposition and, afterwards, with the deposited diamond [13,[16][17][18][19][20][21][22][23]; iii) the use of interlayer materials with intermediate thermal expansion coefficient between WC-Co and diamond to relieve the residual thermal stresses [13,[19][20][21][22][23]; iv) the heat treatment of as-ground WC-Co to modify the substrate surface morphology and reduce surface Co concentration by decarburization of the external layers of the tungsten carbide, resulting in the formation of an outermost layer of metallic tungsten [24] or the re-sintering of WC-Co substrates in a protective atmosphere [25]; v) the micro-roughening of WC-Co surface morphology by selective attack of the tungsten carbide with Murakami's reagent (K 3 Fe(CN) 6 : KOH: H 2 O = 1: 1: 10) [26] or by multiple laser pulses having irradiation densities ranging from 3.0 to 6.0 J/cm 2 [27], with both techniques requiring a further step in which surface Co is chemically etched.…”