Development of ZrO 2–WC composites by pulsed electric current sintering (original) (raw)
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Frontiers of Materials Science, 2011
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.
Processing of ultrafine ZrO2 toughened WC composites
Journal of the European Ceramic Society, 2009
The interrelationships between the dispersion of the secondary ZrO 2 phase and the material properties of WC-based composites with up to 10 vol% of ZrO 2 are investigated. The homogeneity of the ultrafine WC-nanometric ZrO 2 powder mixtures was optimized by means of multidirectional milling and bead milling. In an alternative route, zirconium butoxide was used as a ZrO 2 source. The composites were fully densified by means of pulsed electric current sintering (PECS), also known as spark plasma sintering, within a few minutes at 1700 • C allowing to maintain an ultrafine grained microstructure combining a hardness of 2600 kg/mm 2 with an indentation toughness of 6 MPa m 1/2 . The ZrO 2 content and Y 2 O 3 stabilization were found to strongly influence the mechanical properties and especially strength of the WC-ZrO 2 composites.
Journal of Alloys and Compounds, 2011
In this investigation, 3 mol% Y 2 O 3 stabilized ZrO 2-based composites reinforced with 10 vol.%, 20 vol.% and 40 vol.% WC (named as 3Y-TZP/10WC, 3Y-TZP/20WC and 3Y-TZP/40WC) were fabricated by using injection molding and sintering. Mechanical properties of these composites varied due to WC addition and dwelling time. Density, strength and toughness decreased with shorter dwelling time and increasing WC content however a significant enhancement in fracture toughness was obtained by 3Y-TZP/20WC composite which had 9.2 MPa m 1/2 toughness. Severe unlubricated wear tests which were performed under 55 N normal load and 45 km sliding distance showed that 3Y-TZP/20WC composite had the lowest wear rate and wear volume values which are 2 × 10 −8 mm 3 /(N m −1) and 0.05 mm 3 , respectively.
Egyptian Journal of Chemistry
M ANUFACTURE of composite materials has become an important issue in recent years due to their high mechanical properties that make them suitable for many applications which needs high wear resistance and high strength. In the present work, (WC-TiC-Co) with 3,6,9,12,15, and20 wt. % ZrO2 composites were prepared by mechanical milling. The mixed powders were pressed in a uniaxial press and sintered at 1450 oC for two different times 1.5 and 3 hrs. The results indicated that the relative density decreases gradually by increasing ZrO2 percent for both sintering times. The microstructure of WC-TiC-Co/ ZrO2 composites indicated the formation of needle shape particles from 0-9 wt. % ZrO2 samples for 1.5 hr. sintering time and disappeared for the others sintered for 3 hrs. Hardness, compression strength, and transverse rupture strength decreased by increasing ZrO2 percent for all samples, but both the wear resistance and fracture toughness increased gradually by increasing ZrO2 wt. % up to 9 wt. % and then decreased for the higher percent's.
ZrO2–WC nanocomposites with superior properties
Journal of the European Ceramic Society, 2007
Fully dense ZrO 2 -based nanocomposites with 5-40 vol.% WC were produced by hot pressing at 1450 • C for 1 h. The hardness and bending strength of the composites increases with increasing WC content, whereas the toughness hardly changes. An exceptionally high strength of 2 GPa combined with a hardness of 14.80 GPa and an excellent fracture toughness of 9.4 MPa m 1/2 was obtained for the 2 mol% Y 2 O 3 stabilised ZrO 2based composite with 40 vol.% WC. Such an attractive combination of properties is quite unique for a ceramic composite and is only matched by WC-Co cermets. The composites are substantially harder and stronger than the fine-grained Y-TZP, whereas the excellent toughness of Y-TZP is maintained. The strength improvement was accompanied with a change in fracture mode of the ZrO 2 grains from intergranular to transgranular. The ZrO 2 -WC nanocomposites were found to slightly plastically deform before fracturing during bending.
Ohji/Advances Processing, 2007
The influence of the material's electrical properties on the pulsed electric current sintering (PECS) behavior of Y-ZrO 2 based ceramic composites is investigated in detail. The current and temperature distributions in the sintering compacts are investigated, using a developed finite element code, and their influence on the material's densification behavior is highlighted. Both zirconia ceramics and zirconia based ceramic composites with improved mechanical properties, as compared to traditionally hot pressed ceramics, could be obtained by PECS.
International Journal of Refractory Metals & Hard Materials, 2011
In this study the W-ZrC composites fabricated by in situ reaction sintering of two precursors were compared, 1-The conventional WC and ZrO 2 which are ball milled with established molar ratio of 3-1 for 12 hours, gelcasted to form a green body and then undergo a pressure less sintering cycle, 2-A new and innovative way in which for the first time ZrSiO 4 was used instead of ZrO 2 , and by testing different molar ratio between WC and ZrSiO 4 it was understood that the optimum ratio is 3-1 once again. Furthermore the starting ZrO 2 and ZrSiO 4 powder were selected in nano size and it was understood that by using nano powders the amount of unreacted and unwanted phase reduce, the reaction progress and the mechanical proprieties improve. Although the reaction sintered WC/ZrO 2 possess better properties, regarding the cost considerations, reaction sintering of WC/ZrSiO 4 is a much cheaper process.