Ultra Hard Composite Materials Thermal Expansion Mismatch
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Solution Overview
Problem
Ultra hard composite materials, such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN), face challenges due to significant thermal expansion coefficient mismatches between primary and secondary particulate materials and the matrix, leading to residual stress fields that can cause micro-cracking and render the materials difficult to produce as useful macroscopic pieces.
Innovation Solution
The introduction of primary and secondary ultra hard particulate materials with specific thermal expansion coefficients relative to the matrix material, where the primary material has a lower coefficient than the matrix and the secondary material has a higher coefficient, allows for the optimization of stress fields by engineering the distribution of these materials within the composite, thereby reducing residual stresses and improving thermo-mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultra hard composite materials are made with primary and secondary particulate materials having different thermal expansion coefficients than the matrix, then the residual stress fields are optimized and micro-cracking is reduced, but the material composition and manufacturing process become more complex
Solution Approach 1:
The patent applies composite materials by combining primary ultra hard particulate material (e.g., diamond, cBN) with secondary ultra hard particulate material (e.g., silicon carbide, silicon nitride) in a matrix material. The secondary material is specifically selected to have a thermal expansion coefficient greater than the matrix, while the primary material has a thermal expansion coefficient lower than the matrix. This composite structure optimizes stress field distribution and reduces micro-cracking by balancing thermal expansion mismatches.
Solution Approach 2:
The patent applies local quality by creating regions with different thermal expansion characteristics within the composite material. The primary ultra hard particles (diamond, cBN) with low thermal expansion are distributed throughout the matrix, while secondary particles (silicon carbide, silicon nitride) with higher thermal expansion are also incorporated. This local variation in thermal expansion properties throughout the material structure helps balance residual stresses and prevent micro-crack formation.
2Stability of the object's composition
If multiple types of ultra hard particulate materials are incorporated into the composite, then the stress field distribution is optimized, but the manufacturing precision and control become more difficult
Solution Approach 1:
The patent applies parameter changes by systematically varying the thermal expansion coefficients of the constituent materials. The primary ultra hard particulate material is selected with a thermal expansion coefficient lower than the matrix (e.g., diamond: 0.8-1.2 ppm/°C, cBN: 1.0-1.5 ppm/°C), while the secondary ultra hard particulate material is selected with a thermal expansion coefficient greater than the matrix (e.g., silicon carbide: 3.5-4.5 ppm/°C, silicon nitride: 3.0-3.5 ppm/°C). This parameter optimization enables control over stress field distribution while managing manufacturing complexity.
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 enables the creation of composite materials with optimized stress field distributions, reducing the likelihood of crack initiation and propagation, and enhancing the material's performance in applications like cutting tools and load-bearing prosthetics by managing thermal expansion mismatches.
Implementation Method 1
the primary ultra hard or hard particulate material has a thermal expansion coefficient lower than that of the matrix material and the at least one secondary ultra hard or hard particulate material has a thermal expansion coefficient greater than that of the matrix material
Data Source
AI summary
The invention provides for an ultra hard or hard composite material comprising a primary ultra hard or hard particulate material and at least one secondary ultra hard or hard particulate material dispersed in a matrix material. The primary ultra hard or hard particulate material has a thermal expansion coefficient lower than that of the matrix material and the at least one secondary ultra hard or hard particulate material has a thermal expansion coefficient greater than that of the matrix material.