Abstract
Ultrafine grained WC-12Co-0.2VC (named UYG12V) cemented carbides were prepared via the two-step spark plasma sintering (SPS) in this study. First, the effects of the sintering temperature on the relative density and WC grain size of UYG12V cemented carbides were studied. The results show that regular WC grains form when sintered at 1300 °C. The sintered body begins to rapidly densify and WC grains grow slowly when sintered at 1200 °C. Thus, the first-step (T1) and the second-step (T2) temperatures in the two-step SPS of UYG12V are 1300 °C and 1200 °C, respectively. The effect of the holding time during the first and second steps on the mechanical properties was also studied. The results show that the UYG12V cemented carbide sintered at 1300 °C for 3 min and then at 1200 °C for 5 min has the best comprehensive mechanical properties, exhibiting the average particle size, Vickers hardness, fracture toughness, relative density, and bending strength of 271 nm, 18.06 GPa, 12.25 MPa m1/2, 99.49%, and 1960 MPa, respectively.
Highlights
Due to its high hardness, high wear resistance, stability at high temperature, and other mechanical properties, cemented carbide is widely used in cutting, drilling, and some mining equipment and components [1]
The relative density of the sample reaches near 99% when sintered at 1300 ◦ C
The liquid appears and the relative density of the sample increases rapidly at sintering temperatures ranging from phase appears◦ and the relative density of the sample increases rapidly at sintering temperatures between 1150 C to 1200 ◦ C, during which the WC grains grow slowly
Summary
Due to its high hardness, high wear resistance, stability at high temperature, and other mechanical properties, cemented carbide is widely used in cutting, drilling, and some mining equipment and components [1]. During preparation of the ultrafine grained cemented carbide, crystal grains are more likely to grow during sintering because nano-WC particles have a lower surface energy than ordinary WC particles [2,3,4], and it is difficult to obtain ultrafine WC grains using conventional sintering. At present, these are two main ways to inhibit WC grain growth: Adding grain growth inhibitors and selecting a rapid sintering process [5,6]. The inhibitor preferentially dissolves and continuously precipitates in the Co phase, which changes the wettability and fluidity of the Co phase and the solubility of WC in liquid Co, affecting the density of the sintered body [10,11]
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