Polycrystalline Diamond Cutting Elements Without Metal Catalysts
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Solution Overview
Problem
Polycrystalline diamond cutting elements used in earth-boring tools face thermal instability and brittleness due to differential thermal expansion rates between diamond and catalyst materials, leading to delamination and reverse graphitization at high temperatures.
Innovation Solution
A method of forming polycrystalline diamond by encapsulating diamond particles, carbon monoxide, and carbon dioxide in a container and subjecting them to high pressure and temperature conditions to form inter-granular bonds, eliminating the need for metal catalysts and reducing graphitic carbon presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If catalyst material is used during HPHT sintering to form polycrystalline diamond, then diamond-to-diamond bonding is promoted and oxidation is reduced, but thermal damage occurs at high temperatures due to differential thermal expansion between diamond and catalyst material
Solution Approach 1:
The patent removes catalyst material from the polycrystalline diamond structure after sintering through leaching processes (acid treatment, electrochemical removal, or laser-induced removal). This extraction eliminates the source of thermal expansion mismatch while preserving the diamond bonding, thereby resolving the contradiction between achieving strong bonding during sintering and maintaining thermal stability during operation.
Solution Approach 2:
The patent performs preliminary removal of catalyst material through controlled leaching or electrochemical processes before the cutting element undergoes service. This preliminary action prevents thermal damage from occurring during high-temperature operation by eliminating the catalyst material that would cause differential thermal expansion, while the diamond structure has already been formed with proper bonding.
2Strength
If catalyst material remains in the diamond table, then the diamond table maintains structural integrity, but internal stress develops at temperatures exceeding 350°C due to differential thermal expansion rates
Solution Approach 1:
The patent selectively removes catalyst material from the polycrystalline diamond structure through leaching processes (acid treatment, electrochemical removal, or laser-induced removal). This extraction eliminates the source of differential thermal expansion that causes internal stress, while the diamond-diamond bonding structure maintains structural integrity without the catalyst material present.
3Ease of manufacture
If catalyst material is present in the diamond table, then diamond formation is promoted during sintering, but reverse graphitization occurs at temperatures of 750°C and above
Solution Approach 1:
The patent removes catalyst material from the polycrystalline diamond structure after sintering through leaching processes (acid treatment, electrochemical removal, or laser-induced removal). This extraction prevents reverse graphitization at high temperatures by eliminating the catalyst material that facilitates the transformation of diamond to graphite, while the diamond structure has already been formed during sintering.
Solution Approach 2:
The patent performs preliminary removal of catalyst material through controlled leaching or electrochemical processes before the cutting element undergoes service. This preliminary action prevents reverse graphitization from occurring during high-temperature operation by eliminating the catalyst material, while the diamond structure has already been formed with proper bonding.
4Reliability
If thermally stable polycrystalline diamond is formed by leaching catalyst material, then thermal stability is improved, but the diamond table becomes more brittle and vulnerable to stresses
Solution Approach 1:
The patent applies partial leaching of catalyst material rather than complete removal. By controlling the leaching process (acid treatment, electrochemical removal, or laser-induced removal) to remove a portion of the catalyst material while leaving some residual material, the patent achieves improved thermal stability while maintaining sufficient catalyst material to prevent excessive brittleness and maintain resistance to mechanical stresses.
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 resulting polycrystalline diamond cutting elements are thermally stable up to higher temperatures, less susceptible to thermal damage, and exhibit improved mechanical properties without the brittleness of fully leached diamond tables.
Implementation Method 1
such polycrystalline diamond cutting elements are formed by sintering and bonding together relatively small diamond grains or crystals under conditions of high temperature and high pressure
Implementation Method 2
subjecting them to high pressure and temperature conditions to form inter-granular bonds
Implementation Method 3
subjecting them to high pressure and temperature conditions to form inter-granular bonds
Implementation Method 4
Catalyst material is mixed with the diamond grains to reduce the amount of oxidation of diamond by oxygen and carbon dioxide during an HPHT process
Implementation Method 5
Catalyst material is mixed with the diamond grains to reduce the amount of oxidation of diamond by oxygen and carbon dioxide during an HPHT process and to promote diamond-to-diamond bonding
Implementation Method 6
This internal stress is at least partially due to differences in the rates of thermal expansion between the diamond table and the cutting element substrate to which it is bonded
Implementation Method 7
The presence of the catalyst material in the diamond table may contribute to thermal damage in the diamond table when the cutting element is heated during use, due to friction at the contact point between the cutting element and the formation
Implementation Method 8
Furthermore, catalyst material may allow diamond within the diamond table to be converted to graphite, which may be referred to in the art as 'reverse graphitization'
Data Source
AI summary
A method of forming polycrystalline diamond includes encapsulating diamond particles, carbon monoxide, and carbon dioxide in a container. The encapsulated diamond particles, carbon monoxide, and carbon dioxide are subjected to a pressure of at least 4.5 GPa and a temperature of at least 1,400° C. to form inter-granular bonds between the diamond particles. A cutting element includes polycrystalline diamond material comprising inter-bonded grains of diamond. The polycrystalline diamond material is substantially free of graphitic carbon and metallic compounds. The polycrystalline diamond material exhibits a density of at least about 3.49 g/cm3 and a modulus of at least about 1,000 GPa. An earth-boring tool may include such a cutting element secured to a body.