Nanograin Diamond Polycrystal With Low Knoop Recovery for Chipping Resistance
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Solution Overview
Problem
Conventional diamond polycrystals used in tools face challenges with high hardness but insufficient toughness and chipping resistance, while ultra-high hardness nano twin-crystal diamond bulk materials have very high hardness but inadequate toughness and chipping resistance.
Innovation Solution
A diamond polycrystal is developed with a Knoop hardness ratio (a′/a) of less than or equal to 0.99, composed of diamond grains with an average size of less than 100 nm, and produced without a binder to enhance hardness and toughness, achieving excellent chipping resistance and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional diamond polycrystal is obtained by sintering diamond powder with sintering aid and binder at high pressure and temperature, then the diamond polycrystal can be manufactured, but the mechanical properties such as hardness and strength decrease due to the presence of sintering aid and binder
Solution Approach 1:
The invention extracts and removes the harmful components (sintering aid and binder) from the diamond polycrystal manufacturing process. By directly converting non-diamond carbon material into diamond without using sintering aid or binder, the patent eliminates the source of mechanical property degradation while maintaining manufacturability through direct phase transformation at high pressure and temperature.
Solution Approach 2:
The invention changes the manufacturing parameters by applying very high pressure (4-25 GPa) and very high temperature (1200-2300°C) to directly convert non-diamond carbon material into diamond. This parameter change enables direct phase transformation without requiring sintering aid or binder, thereby maintaining both manufacturability and high mechanical properties.
2Temperature
If sintering aid is removed by acid treatment to improve heat resistance, then heat resistance improves, but hardness and strength become low and mechanical properties are insufficient
Solution Approach 1:
The invention performs preliminary action by preventing the incorporation of sintering aid and binder during the diamond formation process itself. By directly converting non-diamond carbon material into diamond without using these additives, the patent eliminates the need for subsequent acid treatment to remove sintering aid, thereby simultaneously achieving high heat resistance and high mechanical properties.
3Strength
If ultra-high hardness nano twin-crystal diamond is obtained by direct conversion of onion-like carbon at very high temperature and pressure, then very high hardness is achieved, but toughness and chipping resistance are insufficient
Solution Approach 1:
The invention optimizes the pressure and temperature parameters within specific ranges (4-25 GPa and 1200-2300°C) to control the diamond formation process. By carefully controlling these parameters, the patent achieves a balance between hardness and toughness, producing diamond polycrystals with excellent mechanical properties including improved chipping resistance compared to ultra-high hardness variants.
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 diamond polycrystal exhibits improved chipping resistance and wear resistance while maintaining high hardness, making it suitable for high-load and precision cutting tools with reduced risk of cutting edge damage.
Implementation Method 1
a non-diamond carbon material, such as graphite, glassy carbon, amorphous carbon, or onion-like carbon, can be directly converted into diamond at very high pressure and temperature without using a sintering aid and the like. A diamond polycrystal is obtained by sintering the non-diamond carbon material at the same time as directly converting from the non-diamond phase to the diamond phase.
Data Source
AI summary
In a diamond polycrystal, a value of a ratio (a′/a) of a′ to a is less than or equal to 0.99 in a Knoop hardness test performed under a condition defined in JIS Z 2251:2009, where the a represents a length of a longer diagonal line of a first Knoop indentation formed in a surface of the diamond polycrystal when a Knoop indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the a′ represents a length of a longer diagonal line of a second Knoop indentation remaining in the surface of the diamond polycrystal after releasing the test load.