Pressureless Sintering of Zirconium Diboride

Chamberlain, Adam L.; Fahrenholtz, William G.; Hilmas, Greg

doi:10.1111/j.1551-2916.2005.00739.x

Cited by 291 publications

(252 citation statements)

References 21 publications

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“…Within the detection limit of the XRD technique, it can be concluded that ZrO 2 and WC phases in the 40 vol.% WC composite are chemically stable when PECS was for 20 min even at 1850°C. The present observation is consistent with the work of Chamberlain et al reporting the direct reaction of ZrO 2 and WC to be thermodynamically favorable only above 1960°C [12]. However, it is in contradiction with other literature reports, revealing the presence of ZrC, W 2 C and even W phases as reaction products in ZrO 2 -WC composites during pressureless sintering in vacuum for 1 h at ≥1750°C [13] and the formation of ZrC when PECS of WC composites with 10 vol.% ZrO 2 for 1.5-4 min at 1700°C and 1800°C [5].…”

Section: Constituent Phasessupporting

confidence: 96%

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

et al. 2011

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ZrO 2 -WC composites exhibit comparable mechanical properties as traditional WC-Co materials, which provides an opportunity to partially replace WC-Co for some applications. In this study, 2 mol.% Y 2 O 3 stabilized ZrO 2 composites with 40 vol.% WC were consolidated in the 1150°C-1850°C range under a pressure of 60 MPa by pulsed electric current sintering (PECS). The densification behavior, microstructure and phase constitution of the composites were investigated to clarify the role of the sintering temperature on the grain growth, mechanical properties and thermal stability of ZrO 2 and WC components. Analysis results indicated that the composites sintered at 1350°C and 1450°C exhibited the highest tetragonal ZrO 2 phase transformability, maximum toughness, and hardness and an optimal flexural strength. Chemical reaction of ZrO 2 and C, originating from the graphite die, was detected in the composite PECS for 20 min at 1850°C in vacuum.

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Section: Constituent Phasessupporting

confidence: 96%

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

et al. 2011

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“…It is generally believed that the oxides of B 2 O 3 and ZrO 2 on the surface of B 4 C and Zr inhibit the densification by promoting coarsening through evaporation condensation at temperatures of 1500°C to 1800°C. [22][23][24] In the present case, it is proposed that any excess carbon in the B 4 C would reduce the B 2 O 3 or ZrO 2 (from oxidation of Zr or from ZrO 2 milling media) by the following reactions: 2ZrO 2 + B 4 C + 3C fi 2ZrB 2 + 4CO (g) and ZrO 2 + B 2 O 3 (l) + 3C fi ZrB 2 + 3CO (g). Recently, it has also been shown that these reactions are thermodynamically favorable at 1000°C and 1044°C, respectively, during vacuum sintering.…”

Section: B Effect Of Nonstoichiometry On Reaction and Densification mentioning

confidence: 97%

Low-Temperature Processing of ZrB2-ZrC Composites by Reactive Hot Pressing

Rangaraj

Suresha

Divakar

et al. 2008

Metall Mater Trans A

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LINGAPPA RANGARAJ, SIRIYARA J. SURESHA, CANCHI DIVAKAR, and VIKRAM JAYARAM Dense ZrB 2 -ZrC and ZrB 2 -ZrC x~0.67 composites have been produced by reactive hot pressing (RHP) of stoichiometric and nonstoichiometric mixtures of Zr and B 4 C powders at 40 MPa and temperatures up to 1600°C for 30 minutes. The role of Ni addition on reaction kinetics and densification of the composites has been studied. Composites of~97 pct relative density (RD) have been produced with the stoichiometric mixture at 1600°C, while the composite with 99 pct RD has been obtained with excess Zr at 1200°C, suggesting the formation of carbon deficient ZrC x that significantly aids densification by plastic flow and vacancy diffusion mechanism. Stoichiometric and nonstoichiometric composites have a hardness of~20 GPa. The grain sizes of ZrB 2 and ZrC x~0.67 are~0.6 and 0.4 lm, respectively, which are finer than those reported in the literature.

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“…[2] Sintering is conducted at temperatures higher than 1700 8C depending on the sintering techniques (pressure assisted or pressureless) and/or sintering aids used. [3][4][5][6][7][8] ZrB 2 sintered bodies are usually manufactured with relatively simple geometrical shapes because their brittleness and high hardness make difficult the mechanical machining. Moreover, the requested diamond machining is usually expensive.…”

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confidence: 99%

Slip Casting of ZrB₂–SiC Composite Aqueous Suspensions

2010

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Zirconium diboride (ZrB 2 ) is a material of particular interest because of the excellent and unique combination of high melting point, high electrical and thermal conductivity, and chemical inertness against molten metals or nonbasic slags. [1] These properties make it an attractive candidate for ultra-high temperature applications where corrosionwear-oxidation resistance is demanded. [2] Sintering is conducted at temperatures higher than 1700 8C depending on the sintering techniques (pressure assisted or pressureless) and/or sintering aids used. [3][4][5][6][7][8] ZrB 2 sintered bodies are usually manufactured with relatively simple geometrical shapes because their brittleness and high hardness make difficult the mechanical machining. Moreover, the requested diamond machining is usually expensive. The electrical conductivity of ZrB 2 would permit the production of complex shaped parts by electrical discharge machining (EDM); however, such a method induces the oxidation of the external surfaces with the consequent formation of superficial flaws. The production of near-net shape components by slip casting could be an advantageous technique to overcome these drawbacks.Aqueous dispersions of ZrB 2 with different dispersants were the subject of previous studies, in particular for the production of 3D components by freeze-form extrusion. [9,10] Recently, high solid loading (45 vol%) slurries of ZrB 2 -SiC composite for slip casting were prepared by using polyethylenimine (PEI) as dispersant and nearly fully dense cones were obtained. [11] The present work deals with the production of near-net shapes from ZrB 2 -based compositions by using slip casting as forming technique. Because it is well-known that the presence of silicon carbide (SiC) in the composition ensures improved strength, toughness, and oxidation resistance with respect the pure ZrB 2 , a ZrB 2 -based composite containing 20 vol% of SiC as secondary phase has been chosen and Si 3 N 4 was used as sintering aid. [2,[12][13][14][15] The effect of two commercial ammonium polyacrylates (Duramax D3005 and Dolapix PC33) on the electrostatic stabilization of the casting slips was investigated in order to select the most proper formulations. In particular, zeta potential measurements in water both on the single powders and on the pre-mixed composite powder were performed. As final components, crucibles of different thickness were produced as green bodies, sintered at 2150 8C and then characterized to highlight the effect of the dispersants on the final microstructures.

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Pressureless Sintering of Zirconium Diboride

Cited by 291 publications

References 21 publications

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

Low-Temperature Processing of ZrB2-ZrC Composites by Reactive Hot Pressing

Slip Casting of ZrB₂–SiC Composite Aqueous Suspensions

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Pressureless Sintering of Zirconium Diboride

Cited by 291 publications

References 21 publications

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

Low-Temperature Processing of ZrB2-ZrC Composites by Reactive Hot Pressing

Slip Casting of ZrB2–SiC Composite Aqueous Suspensions

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Slip Casting of ZrB₂–SiC Composite Aqueous Suspensions