cBN Sintered Tool Layering for Thermal Management
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Solution Overview
Problem
Tools made of high-cBN content sintered bodies face issues with chipping due to high thermal conductivity, leading to inefficient cutting and plastic working, especially with difficult-to-machine materials like iron-based sintered alloys, where friction heat escapes, preventing the work material from softening and causing mechanical damage to the tool.
Innovation Solution
Incorporating a heat insulating phase with specific compounds like Al, Si, Ti, Zr, Mo, Ni, and Cr, and a binder phase with elements like Ti, W, Co, and Cr, to control thermal conductivity and maintain high hardness, ensuring the cBN sintered body has a balanced composition and structure that reduces thermal conductivity while enhancing hardness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-cBN content sintered body is used to improve hardness and chipping resistance, then the tool exhibits excellent wear resistance and toughness, but the high thermal conductivity causes friction heat to escape, preventing work material softening and leading to chipping
Solution Approach 1:
The patent applies local quality by creating a layered structure where the first cBN sintered body layer (high cBN content ≥80 vol%) provides hardness and chipping resistance at the cutting edge, while the second cBN sintered body layer (lower cBN content 50-70 vol%) with lower thermal conductivity manages heat. This spatial differentiation of material properties resolves the contradiction between needing high hardness and managing thermal conductivity.
Solution Approach 2:
The patent uses composite materials by combining two different cBN sintered body compositions in a layered structure. The first layer uses high-cBN content material for mechanical strength, while the second layer uses lower-cBN content material for thermal management. This composite approach allows simultaneous achievement of hardness and controlled thermal conductivity.
2Manufacturing precision
If cutting speed is increased to improve surface roughness, then the temperature of work material is raised, but wear rapidly develops and satisfactory tool life cannot be obtained
Solution Approach 1:
The layered structure allows different regions of the tool to have different thermal properties. The second layer with lower thermal conductivity acts as a thermal barrier that maintains elevated temperatures at the cutting interface longer, enabling improved surface finish while the first layer provides wear resistance, thus extending tool life even at higher cutting speeds.
Solution Approach 2:
The patent transitions from a single-layer to a multi-layer structure, adding the dimension of thermal gradient management. This layered architecture enables independent optimization of mechanical properties in one layer and thermal properties in another, resolving the trade-off between surface quality and tool life.
3Temperature
If cBN content is less than 80 volume % to prevent rapid cooling of workpiece, then thermal conductivity becomes relatively low and heat generated by working is less likely to flow out to the tool, but a binder phase poorer in strength and toughness becomes dominant, causing the tool to be chipped in early stage
Solution Approach 1:
The patent segments the tool into two distinct layers, each optimized for different functions. The first layer (cBN ≥80 vol%) maintains strength and toughness, while the second layer (cBN 50-70 vol%) provides lower thermal conductivity for heat retention. This segmentation allows both requirements to be satisfied simultaneously without compromise.
Solution Approach 2:
By creating a composite structure of two different cBN sintered body compositions, the patent achieves both high strength (from the first layer) and low thermal conductivity (from the second layer), resolving the contradiction between maintaining workpiece temperature and preserving tool 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
This approach results in a tool with improved cutting performance, reduced surface roughness, and extended tool life by effectively managing heat conduction and hardness, preventing chipping and enhancing the quality of worked surfaces.
Implementation Method 1
a heat insulating phase having a thermal conductivity of not more than 30 W/m*K
Implementation Method 2
a binder phase having an average particle size of not more than 100 nm
Data Source
AI summary
A tool made of a cubic boron nitride sintered body which has a long life in a stable manner in any application of cutting and plastic working is provided. The tool made of the cubic boron nitride sintered body according to the present invention includes a cubic boron nitride sintered body at least at a tool working point and it is characterized by satisfying an Equation (I) and any one of an Equation (II) and an Equation (III) where a ratio of cubic boron nitride contained in the cubic boron nitride sintered body is denoted as X volume % and thermal conductivity of the cubic boron nitride sintered body is denoted as Y (W/m●K).