In-situ elongated aluminium borate grains toughening WC- 1.87 wt % Al2O3- 4.13 wt % ZrO2 composite via spark plasma sintering

In this work, a novel way was developed to facilitate the sintering of a binderless cemented carbide with Al 2 O 3 contain while improving its toughness. WC- 1.87 wt % Al 2 O 3 - 4.13 wt %ZrO 2 cemented carbides with 1 wt % B 2 O 3 as additives were consolidated by high energy ball-milling and spark plasma sintering the as-milled composite powders. The effects of 1 wt % B 2 O 3 content on the sintering behaviour, microstructure and mechanical properties of the obtained cemented carbides were investigated. The presence of B 2 O 3 significantly lowers the sintering temperature by forming liquid phase and react with Al 2 O 3 which contributed to obtaining fully dense specimens at 1350 °C and maintains fine grain sizes of WC until the temperature exceeding 1450 °C. The sintering temperature of the specimens with optimum mechanical properties has been also reduced comparing that of the original WC- 1.87 wt % Al 2 O 3 - 4.13 wt %ZrO 2 cemented carbides. Furthermore, the addition of B 2 O 3 triggered the reaction between B 2 O 3 and Al 2 O 3 resulting in forming in-situ elongated aluminium borate grains (A 4 B 2 O 9 and A 18 B 4 O 33 whiskers), which promoted the toughness. The specimens sintered at 1450 °C exhibited optimal mechanical properties: the Vickers hardness and fracture toughness were 19.26 GPa and 11.49 MPa m 1/2 , respectively.