Effects of Cr3C2, VC, and TaC on Microstructure, WC Morphology and Mechanical Properties of Ultrafine WC–10 wt. % Co Cemented Carbides

Abstract

In this study, the effects of Cr3C2, VC, and TaC on microstructure, WC grain morphology and mechanical properties of WC–10 wt. % Co ultrafine cemented carbides were investigated. The experimental results showed that WC grains size decreased and size distribution became narrow by adding Cr3C2, VC, and TaC. The inhibition efficiency was in the order of VC > Cr3C2 > TaC. Cr3C2 addition would induce triangular prism grains and Co phase was strengthened by Cr3C2, resulting in the enhancement of transverse rupture strength (TRS) and impact toughness. WC morphologies in cemented carbides with VC addition were triangular prisms with multi-steps in basal and prismatic planes due to anisotropic growth. The multi-steps in basal and prismatic planes led to low TRS and fracture toughness. The inhibition mechanism of TaC is to reduce the surface energy of WC and slow down the solution/re-precipitation rate at the WC/Co interfaces by adsorbing on the surface of WC grains. The sample with 0.8 wt. % Cr3C2 had excellent comprehensive mechanical properties. Its Vickers hardness, fracture toughness, TRS and impact toughness were 1620 kg/mm2, 9.94 MPa·m1/2, 3960 MPa and 50.4 J/m2, respectively. In summary, Cr3C2 is the first choice as the grain growth inhibitors (GGI) for the preparation of ultrafine cemented carbides.

Microstructure and Properties of Fine-Grained WC-10Co-0.5Cr3C2-1TaC-0.5Ru Prepared by Rolling Ball Milling and Low-Pressure Sintering

“…With the increase in sintering temperature, the fracture toughness of sintered samples increased from 13.2 MPa•m 1/2 to 15.3 MPa•m 1/2 . The reason is that the fracture toughness of alloys is mainly dependent on the WC grain size when the Co content remains constant [24]. The finer the WC grain size of the sintered sample, the lower the fracture toughness, and vice versa [57].…”

“…Thus, a rise in sintering temperature will increase grain size, increasing fracture toughness. the WC grain size when the Co content remains constant [24]. The finer the WC grain size of the sintered sample, the lower the fracture toughness, and vice versa [57].…”

“…The results show that Cr 3 C 2 , TaC, and Ru can effectively inhibit the grain growth of WC, and the organization is more uniform so that the cemented carbide has good comprehensive mechanical properties [21][22][23]. Among them, Cr 3 C 2 can refine the grain, enhance the hardness, transverse fracture strength, and impact toughness [24,25]. TaC can improve the red hardness of cemented carbide, and Ru can improve the fracture toughness and service life of carbide tools [22].…”

Joint Low-Temperature Carbothermic Synthesis of WC-Co Alloy in Vacuum

“…It is known that the morphology of the WC grain in WC-Co hard alloys with the addition of Cr3C2 is a triangular prism, and the cobalt bond is reinforced with chromium carbide, which increases the strength of the material. The addition of VC leads to the formation of grains in the form of a triangular prism with multiple steps on the basic and prismatic planes due to the anisotropy of growth, which reduces the strength and crack resistance [8]. If we analyze the morphology of tungsten carbide grains in the alloys obtained as a result of sintering, we can say with confidence that in reality the mechanism of grain growth and shaping follows the above rules.…”

Influence of Cr3C2 and VC Content on WC Grain Size, WC Shape and Mechanical Properties of WC–6.0 wt. % Co Cemented Carbides

“…The reason can be attributed to the ratio of (V, W) Cx segregation layers between (0001) basal facets and {10 0} prismatic facets is much higher than that of (Cr, W) Cx [ 35 , 36 ]. Therefore, WC grains are stacked along [0001] direction to form multi–steps based on (0001) basal planes [ 37 ]. As VC content increases from 0.25 to 0.6 wt.…”