Tungsten Carbide TSP Insert Brazing Method
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Solution Overview
Problem
Existing methods face challenges in securely attaching ultra-hard materials like polycrystalline diamond (PCD) and thermally stable polycrystalline diamond (TSP) to steel surfaces, particularly on stabilizers and drilling bits, due to differential thermal expansion and reactivity issues, as well as difficulties in maintaining a strong bond on curved surfaces during drilling operations.
Innovation Solution
A method involving forming a tungsten carbide body with a slot or pocket, inserting an ultra-hard body, and brazing it within the slot or pocket as a separate step before attaching it to the substrate, using a first braze material in a controlled environment to ensure a stable bond, and then flame-spraying a second braze for attachment, with the tungsten carbide body shielding the ultra-hard material from direct flame exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TSP is brazed directly to steel substrate using conventional methods, then attachment is achieved, but the TSP overheats and loses chemical stability
Solution Approach 1:
A tungsten carbide body serves as an intermediary component between the TSP ultra-hard body and the steel substrate. The TSP is brazed to the tungsten carbide body in a controlled process, and the composite insert is then brazed to the substrate. This intermediary structure allows the TSP to be attached reliably while protecting it from direct exposure to high-temperature flame spray brazing that would cause overheating and chemical degradation.
Solution Approach 2:
The attachment process is segmented into two distinct steps: first brazing the TSP to the tungsten carbide body in a controlled atmosphere to avoid overheating, then brazing the composite insert to the substrate using flame spray. This segmentation allows each brazing operation to be optimized for its specific requirements, protecting the TSP while achieving reliable attachment.
2Strength
If flame spray brazing is used to attach insert to substrate, then strong bond is achieved, but ultra-hard material is exposed to direct flame and overheats
Solution Approach 1:
The tungsten carbide body acts as a mediator that absorbs the direct flame exposure during spray brazing. Its position between the flame source and the TSP ultra-hard material protects the TSP from thermal damage while still allowing the brazing process to create a strong bond between the composite insert and the substrate.
Solution Approach 2:
The tungsten carbide body, positioned to receive direct flame exposure, converts the potentially harmful thermal energy into a beneficial bonding process. The flame heats the tungsten carbide and substrate to create strong brazed joints, while the TSP is protected from direct flame contact, transforming what would be a harmful exposure into a controlled bonding operation.
3Strength
If PCD is used for hard facing, then hardness is improved, but chemical reactivity with steel causes degradation
Solution Approach 1:
The tungsten carbide body serves as a sacrificial or protective layer that can withstand chemical reactions with the steel substrate and brazing materials. This intermediary layer protects the more valuable and chemically sensitive TSP ultra-hard material from direct contact with reactive environments, allowing the TSP to maintain its chemical stability and hardness properties.
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 allows for a robust and controlled attachment of ultra-hard materials, preventing overheating and maintaining the chemical stability of TSP, ensuring a durable and effective wear-resistant surface on stabilizers and drilling tools.
Implementation Method 1
fixing the ultra-hard body therein by brazing said ultra-hard body in the slot or pocket of the tungsten carbide body using a first braze material
Implementation Method 2
flame-spraying a second braze for attachment
Implementation Method 3
the ultra-hard body is shielded by the tungsten carbide body from direct washing with flame in a flame-spray brazing step employed to braze the inserts to the substrate
Data Source
Figure 1~3
Figure 4a~4b
Figure 5~6
AI summary
A method of hard facing a wear surface comprises the steps of forming a tungsten carbide/TSP insert by forming a tungsten carbide body (12) in a mould. After the moulding step, a channel section slot (24) or pocket (24') is created in the body. A TSP body (32) is fitted in the slot/pocket (24/24') so that it is a close sliding fit between the sides (18) of the slot, and is of the same depth as the slot. The TSP is brazed into the slot. The insert has pips (30) on its edges (18) to facilitate welding to a substrate prior to a final brazing step that attaches the insert to the wear surface substrate.