Understanding the Process and Structure of Sintered Diamond

Sintered diamond, also known as polycrystalline diamond (PCD), is an advanced material used in various industrial applications due to its exceptional hardness and wear resistance. The process of making sintered diamond involves combining high-purity diamond dust with a metal binder and subjecting it to high temperatures and pressures. This article will provide a detailed breakdown of the process and the resulting structure of sintered diamond, elucidating the role of diamond particles and their interactions.

Process of Making Sintered Diamond

Preparation of Materials:

Diamond Dust: High-purity diamond particles, derived from natural sources or synthetic processes, are used. Metal Binder: Commonly metals such as cobalt, nickel, or iron are used as binders, selected for their ability to facilitate the sintering process and provide toughness.

Mixing: The diamond dust and metal binder are mixed together using mechanical techniques to ensure an even distribution of diamond particles within the binder.

Compaction: The mixture is compressed into a desired shape using a hydraulic press. This step increases the density of the material, making it suitable for the sintering phase.

Sintering: The compacted mixture is then subjected to high temperatures (typically 1200-1500°C) and pressures (around 5-10 GPa) in a controlled environment, often under vacuum or inert gas conditions. This causes the metal binder to melt and flow, filling the spaces between the diamond particles. Simultaneously, the heat facilitates the bonding of diamond particles at their contact points.

Cooling and Solidification: The material is slowly cooled after sintering, during which the metal binder solidifies, locking the diamond particles in place and forming a solid composite material.

Structure of Sintered Diamond

Interparticle Contact

One of the critical aspects of the structure of sintered diamond is the interparticle contact. The diamond particles do indeed touch each other at various points, which is essential for the material's mechanical properties. This contact enables the efficient transfer of loads between the diamond grains, contributing to the overall strength and durability.

Grain Structure

The resulting structure is polycrystalline, meaning it consists of many small diamond crystals interconnected. The interlocking nature of these diamond particles is a key factor in the hardness and wear resistance of the material. These particles are held together by the metal binder, which also provides additional structural support and increases the material's toughness.

Metal Binder Distribution

The metal binder is evenly distributed throughout the diamond matrix, improving the overall toughness and reducing brittleness. The presence of the binder also allows for some ductility, making the material less prone to fracture compared to pure diamond.

Summary

In summary, sintered diamond is created by mixing diamond dust with a metal binder, compacting the mixture, and then applying heat and pressure to bond the particles. The final structure consists of touching diamond particles held together by a metal matrix, providing a combination of hardness and toughness ideal for various industrial applications.