Simultaneously high fracture toughness and transverse rupture strength in ultrafine cemented carbide

Preparation and mechanisms of cemented carbides with ultrahigh fracture strength

“…It is generally considered that liquid-state sintering consists of three stages (Breval et al, 2005;Wei et al, 2013;Kingery, 1959): (i) the initial fluid flow stage where the rearrangement of particles takes place; (ii) the subsequent solution-precipitation process that gives closer packing and causes grain coarsening; and (iii) the final densification. From the analysis of microstructural characteristics in x3, a diagram is proposed in Fig.…”

“…On the submicrometre or nanoscale, WC or WC-Co powders were synthesized by methods such as mechanical alloying (Wang et al, 2015), chemical vapour deposition (Chen et al, 2014), direct carbonation (Luković et al, 2015) and electro-discharge (Shabgard & Najafabadi, 2014). To avoid rapid grain coarsening during the heating process, various sintering techniques have been developed, from conventional vacuum sintering (Breval et al, 2005) and hot pressing (Fang, 2005) to hot isostatic pressing (HIP) ( (Shi et al, 2006;Wei et al, 2013;Xie et al, 2014;Ekroth et al, 2000), microwave sintering (Fang et al, 2009) and spark plasma sintering (Liu et al, 2012). Also, separate from the choice of powder metallurgy method, a grain growth inhibitor (GGI) is often added to sintering powders to control grain growth while the density of the cemented carbide approaches its maximum in the densification process (Fang, 2005;Shi et al, 2006;Wang et al, 2015;Xie et al, 2014;Shi, Shao, Duan, Yuan & Lin, 2005;Egami et al, 1989).…”

Characterization and comparison of grain boundary character distributions in cemented carbides with different binder phases

“…Binder phase type is thought to be an essential element in both structure development during sintering and crack evolution during application of cemented carbides [2,22]. Previous literatures mainly concern the role of the binder phases in the form of the mean free path (the distance separating carbide grains), and to a lesser extent, the contiguity between carbide or binder phases [1,[23][24][25]; however, the impact of different binder phases on the GBCD within the cemented carbides has not been extensively investigated. Accordingly, the major purposes of present work are as follows: first, to preliminarily check whether the different binder phases can affect the GBCD; second, to investigate the population of special boundaries in cemented carbides; finally, to study the geometry feature of 90°/[10 À10] boundary traces and the possible connection to the performances of cemented carbides.…”

Change in Strength, Hardness and Cracking Resistance in Transition From Medium-Grained to Ultrafine Hard Alloy

“…Ведущим мировым производителем твердых сплавов -международной корпорацией «Sandvik» [14] -была разработана следующая классификация WC-Co-сплавов по среднему диаметру зерен WC, мкм: Одним из вопросов при производстве ультрамелкозернистых ТС является рост твердости при переходе от субмикронных к ультрамелкозернистым твердым сплавам, который, согласно некоторым исследователям, замедляется [15], ограничивается [16,17] либо инвертируется [18]. Второй неразрешенный вопрос -возможное повышение трещиностойкости при приближении к нанодиапазону размеров зерен за счет реализации недислокационных механизмов скольжения [3,4,6,[19][20][21][22]. И наконец, третьим вопросом является наличие зависимости прочности от среднего диаметра зерен при переходе к ультрамелкозернистым сплавам, которая может превышать 5000 МПа [23] или быть ниже 500 МПа [24].…”