Abstract
Abstract High-density WC–Ni composite ceramics were prepared by cold isostatic pressing–vacuum pressureless sintering–hot isostatic pressing with tungsten carbide (WC) powder and NiCl2·6H2O as a binder. Results show that with an increase in the contents of Ni in the metal binder phase, the relative density of WC–Ni composite ceramics is improved, and the formation of the carbon-deficient W2C phase is reduced. There is no W2C generated in the WC–1 wt% Ni material. At high temperatures, the Ni phase changes into the liquid phase and enters between the WC particles, thereby promoting the close alignment of the WC particles. Moreover, the WC particles will be more closely aligned under their own surface tension and capillary action, thereby promoting the densification of WC–Ni composite ceramics. The WC–0.5 wt% Ni composite ceramics are fully dense and show the best comprehensive performance with a microhardness of 23.0 GPa, a fracture toughness of 5.28 MPa m1/2, and a flexural strength of 1,396.58 MPa. WC–Ni composite ceramics are mainly composed of elongated triangular prism WC particles and Ni phase. Transgranular fracture was the main fracture mode of WC–Ni multiphase ceramic materials with a small amount of intergranular fracture due to the existence of the Ni phase. Such a fracture mode can increase the flexural strength of the composite material.
Highlights
Cemented carbides are obtained by the powder metallurgy preparation process, using a hard compound of refractory metal as the matrix and adding a transition metal as a sintering aid
An increase in the liquid-phase Ni accelerates the movement of with tungsten carbide (WC) particles and, on the other hand, promotes its homogeneous distribution around WC particles, expediting the densification process
From the results of the specimen densification of WC–Ni composite ceramics with 0.25, 0.5, and 1 wt% Ni metal binder phases after vacuum pressureless sintering (VPS) at 1,530 and 1,560°C and hot isostatic pressing (HIP), the analysis shows that WCN-4#, the ceramic material of WC–0.5 wt % Ni sintered at 1,560°C, has the best densification degree, reaching 100.13%, indicating that the material is completely dense
Summary
Cemented carbides are obtained by the powder metallurgy preparation process, using a hard compound of refractory metal as the matrix and adding a transition metal (such as cobalt, nickel, and iron) as a sintering aid. Due to its excellent combination of high strength, high hardness, and high wear resistance, it is widely used in cutting tools, mining, wear parts, drilling, metal cutting, molds, and other fields [1,2,3,4,5,6,7,8]. WC-based cemented carbides have low toughness and sinterability [11] This is because the WC material has a hexagonal crystal structure, and carbon atoms exist in the gap of the tungsten metal lattice to form gap solid solution. It is difficult to sinter densified WC materials by conventional sintering methods (such as hot press sintering and vacuum pressureless sintering (VPS)) [12]
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