Densification and microstructure development in spark plasma sintered WC–6 wt% ZrO₂ nanocomposites

Abstract

In this paper, we report the results of a transmission electron microscopy investigation on WC–6 wt% ZrO2nanocomposite, spark plasma sintered at 1300 °C, for varying times of up to 20 min. The primary aim of this work was to understand the evolution of microstructure during such a sintering process. The investigation revealed the presence of nanocrystalline ZrO2particles (30–50 nm) entrapped within submicron WC grains. In addition, relatively coarser ZrO2(60–100 nm) particles were observed to be either attached to WC grain boundaries or located at WC triple grain junctions. The evidence of the presence of a small amount of W2C, supposed to have been formed due to sintering reaction between WC and ZrO2, is presented here. Detailed structural investigation indicated that ZrO2in the spark plasma sintered nanocomposite adopted an orthorhombic crystal structure, and the possible reasons for o-ZrO2formation are explained. The increase in kinetics of densification due to the addition of ZrO2is believed to be caused by the enhanced diffusion kinetics in the presence of nonstoichiometric nanocrystalline ZrO2.

Mechanical and tribological characteristics of tungsten cermet composites sintered with Co-based and zirconia mixed binders

“…A noteworthy observation from the micrographs is the increase in the average grain/phase size in the composites with increase in the zirconia content. This is in contrast with the familiar tendency of zirconia in WC-ZrO 2 based cermets where it is reported to reduce the tendency towards grain growth [9]. This suggests that the sintering mechanism in the presence of both metallic and zirconia binders is significantly altered resulting in larger grain sizes with increased zirconia content.…”

“…Notably, their tendency to soften at high temperature, relative low oxidation and corrosion resistance, and relatively low fracture toughness highlights their limitations [6,7]. Resulting from these limitations, a number of works on improvement of properties of tungsten cemented carbide based cermets through compositional formulations and improved synthesis techniques have been reported [8,9].…”

“…Complete replacement of metallic binders with ceramic sinter additives for the sintering of tungsten carbide based cermets has been the most explored approach and reported to offer a lot of promise [9,10]. Zirconia which has been majorly explored as a ceramic sinter additive has the advantages of improving wear, toughness, hardness, high temperature and chemical stabilities of the cermets [11,12].…”

Microstructure and mechanical properties of Al2O3 matrix nanocomposites produced by solid state precipitation

“…[1][2][3][4][5][6][7][8][9][10][11] In particular, it has been established that the incorporation of nanocrystalline SiC in an alumina matrix can result in an improvement of strength by ∼20% or more and of the resistance to severe wear by a factor of ∼3. 1,4,[7][8][9]12 In addition to the extensive research on Al 2 O 3 -SiC nanocomposites, other nanocomposites based on alumina, such as Al 2 O 3 -TiC, 10 Al 2 O 3 -TiCN-SiC, 11 have also been developed with all showing improved properties with respect to monolithic alumina.…”

Processing and characterization of WC–10Ni/–7Ni–3Cr based yttria stabilized zirconia spark plasma sintered composites

“…In this regard, cemented carbides developed using metallic binder additives have been observed to have some limitations [7,8]. At high temperatures for instance, WC based cermets sintered with metallic binders are prone to softening, show a higher susceptibility to corrosion and oxidation, and reduced shock resistance [9,10]. Low competence of metallic bond cemented carbide under the afore-stated conditions has led to research efforts to overcome its limitations.…”