Effect of SiC nanowhisker addition on microstructure and mechanical properties of regenerated cemented carbides by low‐pressure sintering

Abstract

Cemented carbide, as an important industrial material, is well-known as "industrial teeth" due to its high hardness, strength, wear resistance, and other fantastic properties, which plays an important role in the fields of petroleum machinery, mining machinery, and mechanical processing. [1][2][3] However, there is a shortage of tungsten (W) and cobalt (Co) resources, which are main raw materials for cemented carbide. Therefore, recycling waste-cemented carbide to prepare regenerated cemented carbide raw materials is of great significance. In general, the hardness and toughness of cemented carbides are a pair of contradictions that are difficult to balance. Hence, it is particularly important to explore highperformance cemented carbide. 4 At present, several effective methods about toughening and strengthening are applied to improve the performance of regenerated cemented carbides based on characterizes and performances of the matrix and the reinforcing materials. The main toughening mechanisms of cemented carbide are whisker toughening, particle toughening, phase transformation toughening, microcrack toughening and layered structure toughening, etc. [5][6][7]

Preparation and toughening mechanism of Mo2NiB2‐based cermets with SiC whiskers

“…Comparing the phases of cermets with different content of SiCw, it is found that the peak of cermets added with SiCw shifts to the right, indicating that the diffraction angle increases and the lattice constant decreases. The reason is that the radius of Si atom is smaller than that of Mo atom and Ni atom, which causes lattice distortion in Mo 2 NiB 2 , and increases the internal energy and internal stress of the material 15 . Then, when the load is applied, the dislocation slip deformation will be hindered.…”

“…Figure 5C shows that when the whisker content is 0.5 wt%, the grain distribution of cermets is the most uniform, in which 1–3 μm grains are the most, and SiCw is uniformly dispersed in cermets. Grain refinement is mainly due to the fact that the dissolved SiCw in the binder phase reduces the supersaturation of the binder phase relative to the hard phase, and reduces the driving force of the hard phase during the dissolution and precipitation of the binder phase 15 . SiCw distributed at the grain boundary inhibits the dissolution of the hard phase in the binder phase.…”

“…The reason is that the radius of Si atom is smaller than that of Mo atom and Ni atom, which causes lattice distortion in Mo 2 NiB 2 , and increases the internal energy and internal stress of the material. 15 Then, when the load is applied, the dislocation slip deformation will be hindered. Therefore, the strength and hardness of the material will be improved.…”

“…Grain refinement is mainly due to the fact that the dissolved SiCw in the binder phase reduces the supersaturation of the binder phase relative to the hard phase, and reduces the driving force of the hard phase during the dissolution and precipitation of the binder phase. 15 SiCw distributed at the grain boundary inhibits the dissolution of the hard phase in the binder phase. SiCw inhibits the dissolution and precipitation mechanism, thus hindering grain growth.…”

“…In addition, the reduction in the grain size will also reduce the friction coefficient of the cermets. 15 To further analyze the wear resistance of SiCw cermets with different contents, a three-dimensional optical surface profiler was used to compare and analyze the wear scars of the five cermets groups. As shown in Figure 12, with increasing SiCw content, the wear surface area of the cermets first decreases and then increases.…”