cBN Sintered Cutting Edge With hBN Gradient for Wear Resistance
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Solution Overview
Problem
Cubic boron nitride (cBN) sintered materials used in cutting tools and anti-wear tools face issues with reduced tool lifetime due to transformation of cBN to softer hexagonal boron nitride (hBN) during laser processing, leading to weakened cutting edges and increased wear, while grinding without hBN results in crater wear and frequent defects.
Innovation Solution
A cubic boron nitride sintered material tool is designed with a controlled ratio of cBN and hBN phases on the cutting edge, where the ratio Iπ*/Iσ* of hexagonal boron nitride to cubic boron nitride intensity is maintained between 0.1 to 2 on the surface and 0.001 to 0.1 at a depth of 5 μm, utilizing hBN's lubricant-like properties to enhance sliding properties and defect resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser processing is used to finish the cutting edge, then the cutting edge shape is improved, but cBN transforms to hBN causing reduced strength and tool lifetime
Solution Approach 1:
The patent applies local quality by creating a gradient structure where only the surface layer (0-5μm depth) contains hBN phase while the deeper layers maintain cBN phase. This localized hBN distribution at the cutting edge surface provides the desired properties without compromising the overall strength of the tool body.
Solution Approach 2:
The patent utilizes parameter changes by controlling the hBN phase ratio through laser processing parameters. By adjusting laser power, scanning speed, and number of passes, the hBN content at the cutting edge is precisely controlled to achieve optimal balance between surface quality and structural integrity, with hBN ratio maintained at specific levels in different depth zones.
2Manufacturing precision
If laser processing is used to finish the cutting edge, then the cutting edge shape is improved, but tool lifetime is reduced due to increased wear
Solution Approach 1:
The patent converts the harmful effect of hBN formation (which normally indicates degradation) into a beneficial feature. By intentionally creating a controlled hBN layer at the cutting edge surface through laser processing, the softer hBN phase acts as a protective layer that reduces wear and improves sliding properties, thereby extending tool lifetime while maintaining cutting performance.
3Strength
If grinding is used instead of laser processing, then hBN transformation is avoided, but crater wear and defects occur frequently
Solution Approach 1:
The patent introduces hBN phase as an intermediary layer at the cutting edge surface that mediates between the cBN tool body and the workpiece material. This hBN intermediary layer with its lubricant-like properties reduces direct contact and friction, preventing crater wear and defects while allowing the underlying cBN structure to maintain its strength.
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 controlled hBN ratio improves the tool's defect resistance by maintaining strength and reducing wear, thereby extending the tool's lifespan and performance.
Implementation Method 1
utilizing hBN's lubricant-like properties to enhance sliding properties and defect resistance
Implementation Method 2
measuring an energy loss associated with excitation of K-shell electrons of boron by electron energy loss spectroscopy using a transmission electron microscope
Data Source
AI summary
A cubic boron nitride sintered material tool contains a plurality of cBN grains. cBN grains located on a surface of the cutting edge contain a cubic boron nitride phase, and a hexagonal boron nitride phase. When a ratio Iπ*/Iσ* between an intensity of a π* peak derived from a π bond of hBN in the hexagonal boron nitride phase and an intensity of a σ* peak derived from a σ bond of hBN in the hexagonal boron nitride phase and a σ bond of cBN in the cubic boron nitride phase is determined by measuring an energy loss associated with excitation of K-shell electrons of boron, the ratio Iπ*/Iσ* of the cBN grain on the surface of the cutting edge is 0.1 to 2, and the ratio Iπ*/Iσ* of the cBN grain at a depth position of 5 μm from the surface of the cutting edge is 0.001 to 0.1.