For conventional polycrystalline diamonds used in tools such as cutting drills, dressers and dies, as well as drills, iron group metals (e.g., Fe, Co and Ni), carbonates (e.g., CaCO3) are used as sintering homogeneous U to promote sintering of raw materials, and ceramics (e.g., SiC) are used as binders to bind raw materials.
The polycrystalline diamonds
were obtained by sintering the diamond powder as raw material with sintering agent under thermodynamically stable high pressure and high temperature conditions (generally, the pressure is about 5 GPa to SGPaJ ^ degree is about 1300 C to 2200 C). The polycrystalline diamond obtained by this method contains the sintering agent used. The sintering agent has a great influence on the mechanical properties of polycrystalline diamond, such as hardness and strength, and on its heat resistance.
It is also known that polycrystalline diamonds with the above sintering agents have been removed by acid treatment, and sintered diamonds with excellent heat resistance using SiC as binder. However, the hardness and strength of these diamonds are low, and their mechanical properties as tool materials are insufficient. At the same time, non-diamond carbon materials (such as graphite, glass carbon or amorphous carbon) can be directly converted into diamond under ultra-high pressure and ultra-high temperature without using sintering agent. Single-phase polycrystalline diamond was obtained by directly converting non-diamond phase into diamond phase and sintering at the same time.