Superhard Cutting Tool Brazing for Even Hardness and Joint Strength
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Solution Overview
Problem
Existing cutting tools face challenges in achieving a strong braze joint with even hardness profiles and high wear resistance, particularly when joining steel and cemented carbide, which can lead to residual stresses, unwanted hardness profiles, and damage to superhard materials like PCD or cBN due to high brazing temperatures.
Innovation Solution
A cutting tool design featuring a maraging steel part with a TiC layer brazed to a cemented carbide substrate using an active brazing process with a Ti-containing braze material, ensuring a consistent hardness profile and strong joint without damaging the superhard material, involving a brazing temperature between 600°C and 780°C and an ageing step to enhance hardness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If induction heating using a coil is used to join steel with cemented carbide, then the braze joint is heated locally, but this leads to unwanted hardness profiles and residual stresses in the steel part
Solution Approach 1:
The patent applies local quality by creating a TiC layer specifically at the interface between the braze material and cemented carbide substrate. This localized chemical reaction zone provides enhanced bonding strength precisely where needed, without affecting the overall hardness profile of the steel part. The TiC layer forms locally during brazing through reaction between Ti in the braze material and C from the cemented carbide, solving the contradiction between local heating effectiveness and global hardness uniformity.
2Strength
If high brazing temperatures are used to strengthen the braze joint, then the joint strength is improved, but the PCD or cBN material is damaged due to graphitization and thermal stresses
Solution Approach 1:
The patent employs parameter changes by carefully controlling the brazing temperature range (600-780°C) and atmosphere (vacuum or inert gas). These parameter optimizations allow the TiC layer to form effectively for strong bonding while preventing graphitization of the PCD or cBN material. The controlled atmosphere and temperature parameters create conditions favorable for TiC formation without reaching the threshold for diamond graphitization, thus resolving the contradiction between joint strength and material integrity.
3Manufacturing precision
If the whole steel and cemented carbide part is heated to make the hardness profile more even, then hardness uniformity is improved, but the overall hardness of the steel part decreases
Solution Approach 1:
The patent applies segmentation by dividing the heat treatment into two distinct stages: (1) brazing at 600-780°C to form the TiC layer and join the parts, and (2) subsequent ageing treatment at higher temperatures to achieve the desired hardness profile in the steel part. This segmented approach allows the braze joint to form under controlled conditions while the steel part's hardness is optimized in a separate process, resolving the contradiction between hardness uniformity and overall hardness retention.
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 a cutting tool with a strong braze joint, even hardness profile, and improved wear resistance, ensuring predictable joint strength and minimizing damage to the superhard material, while allowing for automated industrial processes and reduced wear on threading.
Implementation Method 1
the braze joint comprises Ti and wherein the braze joint comprises a TiC layer with a thickness of between 0.03 and 5 μm adjoining to the cemented carbide
Implementation Method 2
one of the most common ways is induction heating using an induction coil
Implementation Method 3
uncontrolled cooling, in homogenous heat distribution (skin effect)
Data Source
AI summary
A tool includes a superhard part of a polycrystalline diamond (PCD) or a cubic boron nitride (cBN) sintered compact bonded to a cemented carbide substrate and a maraging steel part, where the cemented carbide substrate and the maraging steel part parts are joined by brazing. The present also relates to the making of such tool. The tool provides a strong braze joint and a steel part that have an even hardness.