Polycrystalline Diamond Cutting Elements With High Compressive Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cutting elements with diamond surfaces experience breakage and delamination due to residual compressive stress at the diamond layer-substrate interface, compromising wear resistance and service life during drilling operations.
Innovation Solution
The cutting elements feature a dome-shaped diamond surface with high compressive stress, engineered with a controlled ratio of cobalt crystal structures and potentially including transition layers, formed through high-pressure/high-temperature processing, to enhance wear resistance and minimize thermal expansion mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a diamond layer is formed on a carbide substrate through high-pressure/high-temperature sintering, then wear resistance is improved, but residual compressive stress causes breakage and delamination
Solution Approach 1:
The patent applies parameter changes by modifying the cooling rate and temperature profile during HPHT processing. Specifically, it uses a controlled cooling rate of 5-50°C per minute and maintains the sintering temperature for 1-24 hours to optimize the diamond layer formation. This controlled parameter adjustment reduces thermal gradients and minimizes residual compressive stress while preserving wear resistance.
Solution Approach 2:
The patent utilizes phase transitions by controlling the crystallization of cobalt from liquid to solid phase during the cooling process. The specific cooling rate regime allows for controlled phase transformation that reduces internal stress. Additionally, the high-pressure/high-temperature process induces phase transition of carbon to diamond structure, creating a stress-managed diamond layer.
2Duration of action of stationary object
If the diamond layer thickness is increased to improve wear resistance, then service life is extended, but residual stress and risk of delamination increase
Solution Approach 1:
The patent employs parameter changes by optimizing the thickness of the diamond layer to specific ranges (50-500 micrometers) and controlling the HPHT processing parameters including pressure (5-15 GPa), temperature (1300-2000°C), and cooling rate. This optimized parameter combination allows achieving sufficient wear resistance and service life while managing residual stress through controlled formation.
3Stress or pressure
If the coefficient of thermal expansion mismatch between diamond layer and substrate is reduced, then residual stress is minimized, but material selection becomes more constrained
Solution Approach 1:
The patent applies parameter changes by modifying the thermal processing parameters including heating rate (1-10°C per minute), holding temperature (1300-2000°C), and cooling rate (5-50°C per minute). These parameter adjustments allow the system to accommodate the inherent thermal expansion mismatch between diamond and carbide substrate, transforming the harmful stress into a manageable state that preserves both wear resistance and structural integrity.
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 increases wear resistance and resistance to crack formation, leading to improved operational service life and reduced breakage, with compressive stress levels exceeding 900 MPa and enhanced cobalt phase ratios contributing to these benefits.
Implementation Method 1
subjecting an assembly of diamond grains to high-pressure/high-temperature processing conditions to form the polycrystalline diamond
Implementation Method 2
the high-pressure/high-temperature process used to sinter the diamond layer, form the PCD and attach the PCD layer to the underlying substrate
Implementation Method 3
The diamond surface may have a high level compressive stress of greater than about 500 MPa, greater than about 900 MPa, greater than about 1,000 MPa, or in the range of from about 900 to 1,200 MPa
Data Source
AI summary
Cutting elements include polycrystalline diamond which may be attached to a substrate. The polycrystalline diamond may have a ratio of cubic to hexagonal cobalt crystalline structures of greater than about 1.2. The polycrystalline diamond may have a high level surface compressive stress of greater than about 500 MPa.