The particle size distribution of cemented carbide plays an extremely critical role in its entire production and application process, and is intricately related to the molding performance and final performance.
First, particle size distribution has a significant impact on the molding properties of cemented carbide. A narrower particle size distribution, especially where fine particles are concentrated, helps improve powder flowability. During the pressing process, powder with good fluidity can fill the mold cavity more evenly, making the density distribution of the compact more uniform, reducing defects caused by density differences, thereby improving the accuracy and stability of molding. On the contrary, when the particle size distribution is too wide and the coarse particles and fine particles are mixed unevenly, it is easy to cause the stratification of the powder during the pressing process, affecting the quality of the compact and the success rate of molding.
Secondly, during the sintering stage, the particle size distribution is closely related to the final properties. Fine-grained cemented carbide powder has a high specific surface area, a relatively fast atomic diffusion rate during sintering, and can achieve densification at a lower temperature. This not only helps save energy, but also reduces grain growth, thereby obtaining a finer and more uniform grain structure and improving the hardness and strength of cemented carbide. When sintering coarse-grained powders, higher temperatures and longer times are required to ensure densification, but this may lead to excessive grain growth and reduced toughness.
Furthermore, particle size distribution affects the wear resistance of cemented carbide. An appropriate proportion of fine-grained hard phase particles can better support and protect the matrix during wear and improve wear resistance. Because fine particles can fill the gaps between coarse particles, forming a denser wear-resistant surface. However, if there are too many fine-grained particles, the overall toughness of cemented carbide may be reduced, and it is prone to peeling when subjected to impact loads, which in turn reduces wear resistance.
From the perspective of fracture toughness, the rationality of particle size distribution is also important. A certain amount of coarse-grained hard phase particles can deflect and bridge cracks inside the alloy, increasing the resistance to crack expansion, thereby improving fracture toughness. However, too many coarse particles will weaken the bonding force of the matrix to the hard phase, and cracks will easily occur at the phase interface when stressed, reducing the overall performance.
In addition, the particle size distribution is also related to the thermal conductivity of cemented carbide. Fine-grained cemented carbide usually has a relatively low thermal conductivity because the fine particles increase the grain boundary area, and the grain boundaries hinder heat transfer. In some application scenarios that require heat dissipation, optimization of particle size distribution can balance the needs of hardness and thermal conductivity.
In actual production, precise control of the particle size distribution of cemented carbide is one of the key links in achieving high-performance products. By adjusting the particle size ratio of the raw material powder and adopting advanced powder processing technology, the ideal particle size distribution can be obtained according to specific application requirements, thereby optimizing the molding performance and improving the final performance, making cemented carbide useful in cutting tools, mining machinery, etc. play a better role in many fields.
