Boron-Doped Polycrystalline Diamond With Oxidation-Resistant Surface
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Solution Overview
Problem
Existing polycrystalline diamond technologies face issues with wear resistance due to boron oxide formation on the surface, leading to oxidation and thermal expansion coefficient mismatches, while boron-free diamonds suffer from oxidation of exposed carbon, resulting in reduced wear resistance.
Innovation Solution
Incorporating boron at the atomic level in polycrystalline diamond, with greater than 90% in isolated substitutional type, and forming a protective oxide film on the surface to enhance wear resistance and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If boron is added to polycrystalline diamond to improve conductivity and hardness, then electrical conductivity and hardness are improved, but boron oxide forms on the surface causing oxidation and thermal expansion coefficient mismatch
Solution Approach 1:
The patent applies local quality by creating a dual-zone structure: the interior maintains high boron concentration (10-1000 ppm) for conductivity and hardness, while the surface layer has reduced boron concentration and forms a protective carbon-rich oxide layer. This spatial differentiation of composition resolves the contradiction between bulk mechanical properties and surface chemical stability.
Solution Approach 2:
The patent creates a composite structure within the polycrystalline diamond, combining boron-doped diamond regions with surface-oxidized carbon layers. The composite consists of diamond crystallites embedded in a matrix with controlled oxidation states, where the surface layer acts as a protective barrier while the interior maintains enhanced mechanical and electrical properties.
2Object-affected harmful factors
If surface is oxidized to form protective layer, then oxidation resistance is improved, but thermal expansion coefficient mismatch occurs
Solution Approach 1:
The patent employs parameter changes by precisely controlling the oxidation state of the surface layer through controlled atmosphere heat treatment. By adjusting temperature, time, and atmosphere composition, the surface is oxidized to form a protective layer with tailored thickness and composition, creating a gradient that buffers thermal expansion differences between the diamond substrate and external environment.
3Reliability
If carbon is exposed on surface without protective layer, then material purity is maintained, but carbon oxidizes leading to reduced wear resistance
Solution Approach 1:
The patent applies preliminary action by pre-oxidizing the diamond surface under controlled conditions before the tool enters service. This creates a stable, protective oxide layer in advance that prevents further oxidation during operation. The surface is deliberately modified beforehand to establish a barrier against environmental oxidation, ensuring long-term wear resistance.
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 solution provides polycrystalline diamond with improved wear resistance and oxidation resistance, maintaining high hardness and reducing friction coefficients, suitable for applications in tools like scribe tools and cutting tools.
Implementation Method 1
the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type
Implementation Method 2
a third step of converting the graphite to diamond by pressure heat treatment in the vessel
Data Source
AI summary
Provided is polycrystalline diamond having a diamond single phase as basic composition, in which the polycrystalline diamond includes a plurality of crystal grains and contains boron, hydrogen, oxygen, and the remainder including carbon and trace impurities; the boron is dispersed in the crystal grains at an atomic level, and greater than or equal to 90 atomic % of the boron is present in an isolated substitutional type; hydrogen and oxygen are present in an isolated substitutional type or an interstitial type in the crystal grains; each of the crystal grains has a grain size of less than or equal to 500 nm; and the polycrystalline diamond has a surface covered with a protective film.