Composite cBN Sintered Material to Reduce Wire Adhesion
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Solution Overview
Problem
Cubic boron nitride sintered materials used in tools often adhere to wire materials during wire drawing, leading to wire breakage or surface scratches, due to friction, which reduces tool life and deteriorates the wire surface condition.
Innovation Solution
A composite sintered material comprising cubic boron nitride grains with high dislocation density and specific median diameters, combined with hexagonal and wurtzite boron nitride grains, which enhances strength, thermal diffusivity, and slidability, reducing adherence and wear during wire drawing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cubic boron nitride sintered material is used as tool material, then hardness and thermal stability are improved, but adherence to wire material increases causing wire breakage and surface scratches
Solution Approach 1:
The patent changes the crystallographic parameters of cubic boron nitride grains by controlling dislocation density (1×10^15 to 1×10^17/m²) and grain size (median diameter 10-500 nm). These parameter changes modify the surface properties and friction characteristics of the tool material, reducing adherence to wire material while maintaining high hardness for cutting performance.
Solution Approach 2:
The patent creates a composite sintered material containing cubic boron nitride grains combined with hexagonal boron nitride grains or wurtzite type boron nitride grains in specific volume ratios (0.015≤(Vh+Vw)/(Vc+Vh+Vw)≤0.5). This composite structure combines the hardness of cubic boron nitride with the lubricating properties of hexagonal/wurtzite boron nitride, reducing wire material adherence while maintaining cutting effectiveness.
2Ease of manufacture
If binder is added to cubic boron nitride sintered material, then sintering is facilitated, but strength and thermal diffusivity decrease
Solution Approach 1:
The patent extracts and eliminates the binder component from the sintered material composition. By using only boron nitride grains (cubic, hexagonal, and/or wurtzite phases) without any binder, the material achieves maximum strength and thermal diffusivity while still being sinterable through direct conversion of hexagonal boron nitride to cubic boron nitride under ultrahigh pressure and temperature conditions.
3Stability of the object's composition
If cubic boron nitride grains with low dislocation density are used, then crystallinity is improved, but toughness and crack resistance decrease
Solution Approach 1:
The patent optimizes the dislocation density parameter to a specific range (1×10^15 to 1×10^17/m²) that balances crystallinity with toughness. This controlled dislocation density provides sufficient crystal structure stability while introducing enough lattice defects to act as stress distribution points, preventing crack propagation and improving overall material toughness.
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 composite sintered material achieves extended tool life without surface deterioration in wire drawing processes by minimizing friction and wear, thanks to its improved hardness, toughness, and crack resistance, while maintaining excellent slidability and wear resistance.
Implementation Method 1
a method has been developed to obtain a cubic boron nitride sintered material including no binder by directly converting hexagonal boron nitride into cubic boron nitride under ultrahigh pressure and high temperature and sintering it at the same time without using a binder
Data Source
AI summary
A composite sintered material includes: cubic boron nitride grains; and hexagonal boron nitride grains or the hexagonal boron nitride grains and wurtzite type boron nitride grains, wherein a dislocation density of the cubic boron nitride grains is more than or equal to 1×1015/m2 and less than or equal to 1×1017/m2, a median diameter d50 of equivalent circle diameters of the cubic boron nitride grains is more than or equal to 10 nm and less than or equal to 500 nm, and a relationship of the following expression 1 is satisfied:0.015≤(Vh+Vw)/(Vc+Vh+Vw)≤0.5, Expression 1:where Vc represents a volume-based content ratio of the cubic boron nitride grains, Vh represents a volume-based content ratio of the hexagonal boron nitride grains, and Vw represents a volume-based content ratio of the wurtzite type boron nitride grains.