Binder-Free Polycrystalline Diamond for Crack-Resistant Cutting Tools
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Solution Overview
Problem
Conventional diamond polycrystals used in cutting tools suffer from breakage resistance and cracking issues due to the presence of sintering aids and binders, which compromise their mechanical properties and heat resistance.
Innovation Solution
A diamond polycrystal composed of cubic and 6H type hexagonal diamond grains, produced without sintering aids or binders, using a non-diamond-like carbon material with controlled graphitization, subjected to specific high-pressure and high-temperature conditions to enhance breakage resistance and hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintering aid or binder is used in conventional diamond polycrystal production, then the diamond polycrystal can be formed at high pressure and high temperature, but the mechanical properties such as hardness and strength decrease
Solution Approach 1:
The patent removes sintering aids and binders from the diamond polycrystal composition entirely, using only diamond powder as the source material. This extraction of harmful components resolves the contradiction by eliminating the source of mechanical property degradation while maintaining manufacturability through direct sintering of pure diamond particles.
Solution Approach 2:
The patent changes the sintering parameters to extremely high pressure (5-8 GPa) and high temperature (1300-2200°C) conditions, which allow diamond powder to sinter directly without requiring sintering aids or binders. This parameter change enables the formation of dense diamond polycrystals with superior mechanical properties.
2Temperature
If sintering aid is removed by acid treatment, then heat resistance improves, but hardness and strength decrease
Solution Approach 1:
Instead of removing sintering aids after sintering (acid treatment), the patent inverts the approach by completely eliminating sintering aids from the sintering process itself. This prevents the formation of weak phases that would require removal, thereby maintaining both heat resistance and mechanical strength simultaneously.
3Temperature
If heat-resistant SiC is used as binder, then heat resistance is improved, but hardness and strength become insufficient
Solution Approach 1:
The patent extracts the binder component (SiC) entirely from the system, demonstrating that diamond polycrystals can be sintered without any binder. This eliminates the trade-off between heat resistance and mechanical strength by showing that neither sintering aids nor binders are necessary under the specified high pressure and high temperature conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting diamond polycrystal exhibits excellent breakage resistance, high hardness, and improved cracking resistance, suitable for high-precision cutting tools with reduced risk of edge breakage and wear.
Implementation Method 1
converting the non-diamond-like carbon material into diamond grains
Implementation Method 2
sintering a diamond powder, which is a source material, together with a sintering aid or a binder at high pressure and high temperature
Data Source
Figure 1
AI summary
A diamond polycrystal includes diamond grains, the diamond polycrystal including a cubic diamond and a 6H type hexagonal diamond, wherein the cubic diamond and the 6H type hexagonal diamond exist in the same or different diamond grains, and a ratio Ab1/Ab2 is more than or equal to 0.4 and less than or equal to 1, Ab1 representing a maximum value of absorption in a range of more than or equal to 1200 cm-1 and less than or equal to 1300 cm-1 in an infrared absorption spectrum, Ab2 representing a maximum value of absorption in a range of more than or equal to 1900 cm-1 and less than or equal to 2100 cm-1.