Tungsten Carbide Caps for TSP Drill Bit Wear Resistance
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Solution Overview
Problem
Existing methods for attaching ultra-hard materials like polycrystalline diamond (PCD) and thermally stable polycrystalline diamond (TSP) to drilling equipment surfaces face challenges due to differential thermal expansion, chemical reactivity, and difficulty in achieving a strong, durable bond, especially on curved surfaces like stabilizers where impacts are transverse.
Innovation Solution
A hard faced surface construction method involving a metal substrate with ultra-hard body inserts coated with tungsten to render them wettable, topped with a tungsten carbide cap, and brazed using a copper-based braze material, allowing for a robust attachment that withstands the rigors of drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ultra-hard materials like PCD or TSP are attached directly to steel substrate, then wear resistance is improved, but bonding reliability deteriorates due to differential thermal expansion and chemical reactivity
Solution Approach 1:
The patent employs a composite material structure consisting of three layers: ultra-hard material (PCD or TSP), intermediate bonding layer (tungsten carbide), and steel substrate. This composite structure resolves the contradiction by introducing an intermediate layer that is compatible with both the ultra-hard material and the steel substrate, thereby maintaining wear resistance while ensuring bonding reliability through proper thermal and chemical compatibility.
Solution Approach 2:
The tungsten carbide intermediate layer acts as a mediator between the ultra-hard material and the steel substrate. This intermediate layer has thermal expansion properties that are intermediate between those of the ultra-hard material and the steel substrate, reducing thermal stress. It also provides a surface that is wettable by braze materials, ensuring reliable bonding while protecting the ultra-hard material from direct contact with reactive braze materials.
2Reliability
If braze material is applied to TSP surface, then bonding is achieved, but chemical stability deteriorates because most braze materials do not readily wet TSP
Solution Approach 1:
The tungsten carbide intermediate layer serves as an intermediary that is wettable by braze materials. This layer provides a surface that facilitates bonding while preventing direct contact between the braze material and the TSP, thereby maintaining the chemical stability of the ultra-hard material while achieving reliable bonding.
3Ease of manufacture
If entire surface is covered with tungsten carbide, then bonding ease is improved, but cost increases and ultra-hard material exposure is reduced
Solution Approach 1:
The patent applies local quality by providing tungsten carbide cap layers only on specific regions of the ultra-hard material inserts, particularly on the periphery and top surfaces where bonding and protection are most critical. This localized application maintains ease of manufacture and bonding while preserving maximum exposure of the ultra-hard material on the working surface, optimizing both manufacturing ease and 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
This method enables a durable and consistent attachment of ultra-hard materials across a large surface area, enhancing wear resistance and preventing detachment during drilling, while controlling the brazing process to maintain the chemical stability of the ultra-hard bodies.
Implementation Method 1
a boundary coating on the ultra-hard body to render the body wettable by first braze material
Implementation Method 2
a tungsten carbide cap brazed with said first braze material to at least the top surface of the ultra-hard body
Implementation Method 3
a second braze material that penetrates the gaps between the inserts and between the contact surface of the bodies and the metal substrate
Data Source
AI summary
A hard faced surface comprises a metal substrate. Inserts are attached to the substrate as a covering layer on the substrate. Each insert comprises a thermally stable polycrystalline diamond (TSP) body (or polycrystalline diamond or cubic boron nitride) having a plan section, a contact surface and a flat top surface. A boundary coating on the ultra-hard body renders the body wettable by first braze material. A tungsten carbide cap is brazed with said first braze material to at least the top surface of the TSP block. The inserts are brazed to the substrate in a closely packed side-by-side formation with a second braze material that penetrates the gaps between the inserts and between the contact surface of the bodies and the metal substrate. The tungsten carbide caps of the inserts provide a gauge for the hard faced surface, which caps are ground in a finishing step exposing the caps and providing the hard faced surface with a desired dimension including an amount of the thickness of the caps.