Gradient CBN Sheet Reduces Thermal Stress
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Solution Overview
Problem
Conventional cubic boron nitride (CBN) composite sheets experience thermal residual stress issues due to differences in thermal expansion coefficients between CBN and cemented carbide, leading to cracking, shedding, and reduced service life during use.
Innovation Solution
A gradient structure CBN composite sheet is developed with a transition layer comprising 4 to 18 layers of CBN and cemented carbide in varying volume fractions, reducing thermal residual stress and enhancing bonding strength through a 3D printing process that optimizes material distribution and production efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional sintering process is used to manufacture CBN composite sheet, then high hardness and wear resistance are achieved, but thermal residual stress causes cracking and shedding reducing service life
Solution Approach 1:
The patent applies local quality by creating a gradient transition layer with varying composition and structure between the CBN layer and cemented carbide substrate. The transition layer has a gradual change in material properties (from high CBN content near the CBN layer to high cemented carbide content near the substrate), which locally adapts the thermal expansion coefficient to reduce thermal residual stress while maintaining the overall hardness and wear resistance of the composite sheet.
Solution Approach 2:
The patent uses composite materials by combining CBN powder, cemented carbide particles, and binder in a gradient transition layer. This composite structure allows the transition layer to have intermediate properties between the CBN layer and the cemented carbide substrate, effectively bridging the thermal expansion mismatch and preventing cracking while maintaining the superhard properties of the CBN layer.
2Reliability
If gradient transition layer is introduced to reduce thermal residual stress, then service life is extended, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the transition layer into multiple discrete layers (typically 3-10 layers) with progressively changing composition. Each layer has a specific thickness and material composition ratio, creating a stepped gradient structure. This segmentation approach simplifies the manufacturing process compared to continuous gradient methods, as each layer can be deposited or sintered as a separate unit while still achieving the overall gradient effect to reduce thermal residual stress.
3Reliability
If multiple gradient layers are used to achieve smooth transition, then thermal stress is reduced, but production time and cost increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the composition parameters (CBN content, cemented carbide content, binder content) and physical parameters (layer thickness, number of layers) of the gradient transition layer. By optimizing these parameters, the patent achieves effective thermal stress reduction with a reasonable number of layers (3-10), balancing the thermal stress resistance with production efficiency. The specific parameter ranges are determined based on the thermal expansion coefficients of the CBN layer and cemented carbide substrate.
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 gradient structure effectively reduces thermal residual stress, enhances bonding strength, and extends the service life of the CBN composite sheet by improving wear resistance and cutting efficiency while reducing production costs.
Implementation Method 1
Due to the difference in thermal expansion coefficient of the two materials, the thermal residual stress at the material interface during the cooling and pressure relief process is large
Implementation Method 2
Adopting a 3D printing manufacturing process can optimize the product performance, improve the production efficiency, and effectively control production costs
Data Source
AI summary
The disclosure provides a gradient structure cubic boron nitride composite sheet and a preparation method thereof. The gradient structure cubic boron nitride composite sheet consists of a cemented carbide substrate, a gradient transition layer, and a CBN layer from bottom to top. The gradient transition layer consists of N gradient layers, and the N is 4 to 18. From bottom to top, there are sequentially a first gradient layer, a second gradient layer, an Nth gradient layer, and so on. Any of the gradient layers consists of CBN and cemented carbide, in which the volume fraction of the cemented carbide in the Nth layer is 5 to 30% less than the volume fraction of the cemented carbide in the N−1th layer, and the volume fraction of the CBN in the Nth layer is 5 to 30% more than the volume fraction of the CBN in the N−1th layer.