Binderless Polycrystalline cBN via HPHT Phase Transition
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Solution Overview
Problem
Existing methods for producing polycrystalline cubic boron nitride (PcBN) bodies with high hardness and abrasion resistance are limited by the presence of a binder phase, which reduces their effectiveness for machining ferrous materials, and the difficulty in scaling up the production of binderless PcBN bodies due to the high pressures required.
Innovation Solution
A method for manufacturing a translucent polycrystalline cubic boron nitride body by converting hexagonal boron nitride to cubic boron nitride at pressures above 7.7 GPa and temperatures above 2100°C, resulting in a binderless material with an absorption coefficient of less than 100 cm−1 at 1064 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a binder phase is added to PcBN to improve toughness and manufacturability, then ease of manufacture is improved, but hardness and abrasion resistance deteriorate
Solution Approach 1:
The invention extracts and removes the binder phase from the PcBN composite material, creating a binderless structure. This is achieved by subjecting hBN to HPHT treatment that directly converts it to cBN without requiring a binder matrix, thereby eliminating the trade-off between manufacturability and hardness
Solution Approach 2:
The invention changes the physical and chemical parameters of the material system by using specific HPHT conditions (pressure >7.7 GPa, temperature >2100°C) that enable direct conversion of hBN to cBN. This parameter change allows the material to form a coherent structure without binder while maintaining manufacturability
2Reliability
If pressure is increased above 7.7 GPa to produce binderless PcBN, then purity and hardness are improved, but device complexity and manufacturing difficulty worsen
Solution Approach 1:
The invention utilizes the phase transition of hBN to cBN under HPHT conditions. By controlling the phase transition at pressures above 7.7 GPa and temperatures above 2100°C, the material transforms into a pure binderless PcBN structure, achieving high purity while the phase transition mechanism itself simplifies the manufacturing approach compared to binder-based methods
3Strength
If binderless PcBN is produced to eliminate matrix phase, then hardness is improved, but manufacturing scalability worsens due to high pressure requirements
Solution Approach 1:
The invention optimizes the HPHT parameters to achieve binderless PcBN formation at pressures above 7.7 GPa and temperatures above 2100°C. These parameter changes enable the direct conversion of hBN to cBN, producing hard binderless material while improving scalability compared to previous methods that required even higher pressures of 9.5 GPa
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 PcBN bodies are highly transparent, hard, and thermally conductive, making them suitable for a wide range of applications, including machining, optical transmission, and heat spreading, while eliminating the limitations imposed by the binder phase.
Implementation Method 1
converting hexagonal boron nitride to cubic boron nitride at pressures above 7.7 GPa and temperatures above 2100°C
Data Source
AI summary
A translucent polycrystalline cubic boron nitride body is provided. It comprises no more than 2 weight % hexagonal boron nitride grains and has an absorption coefficient of less than 100 cm−1 at a wavelength of 1064 nm.