Cemented Carbide Tool Brazing via Cobalt Gradient
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Solution Overview
Problem
Cemented carbide tools with low cobalt content are unsuitable for brazing due to poor wettability and bonding issues, limiting their use in cutting, drilling, or crushing applications, as low cobalt content affects the strength of the braze joint.
Innovation Solution
A method involving a powder mixture with a cobalt content ≤5.5 wt% is used, where a cobalt gradient is induced by applying a grain growth inhibiting and promoting compound, increasing cobalt content from the tip region to the base surface, enabling a strong braze joint with a steel holder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If low cobalt content cemented carbide body is used, then grain growth is inhibited and cutting performance is improved, but wettability by solder deteriorates and braze joint strength decreases
Solution Approach 1:
The patent applies different cobalt content levels to different regions of the cemented carbide body. The tip region has low cobalt content (≤5.5 wt%) for grain growth inhibition and cutting performance, while the base surface has high cobalt content (≥4.5 wt%) for good wettability and strong braze joint. This spatial differentiation of material properties resolves the contradiction between cutting performance and joint strength.
Solution Approach 2:
The patent creates a cobalt gradient in advance during the sintering process by controlling the diffusion of cobalt from the base surface toward the tip region. This preliminary establishment of non-uniform cobalt distribution ensures that both regions have the required cobalt content before the brazing operation, preventing wettability issues that would arise if uniform low cobalt content was used throughout.
2Stability of the object's composition
If uniform low cobalt content is maintained throughout the cemented carbide body, then overall grain growth is controlled, but the base surface becomes unsuitable for brazing
Solution Approach 1:
The patent deliberately creates local variation in cobalt content rather than maintaining uniform composition. The base surface region is enriched with cobalt to ensure brazing feasibility, while the tip region maintains low cobalt content for grain growth control. This local quality differentiation allows both requirements to be satisfied simultaneously.
Solution Approach 2:
The patent changes the cobalt content parameter spatially across the cemented carbide body. By controlling the cobalt concentration to be ≥4.5 wt% at the base surface and ≤5.5 wt% at the tip region, the patent optimizes both brazing feasibility and grain growth control through parameter variation rather than uniform parameter setting.
3Reliability
If cobalt content is increased to improve braze joint strength, then wettability improves, but grain growth increases and cutting performance deteriorates
Solution Approach 1:
The patent applies high cobalt content locally at the base surface to improve wettability and braze joint strength, while maintaining low cobalt content at the tip region to prevent grain growth and preserve cutting edge strength. This localized application of different material compositions resolves the contradiction between joint strength and cutting performance.
Solution Approach 2:
The patent segments the cemented carbide body into functionally distinct regions with different cobalt content. The base surface segment has high cobalt for brazing, while the tip segment has low cobalt for cutting. This segmentation allows each region to be optimized for its specific function without compromising the other.
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 cobalt gradient ensures a strong bonded braze joint despite low mean cobalt content, allowing for effective attachment of cemented carbide tools to steel holders, enhancing their durability and performance in cutting, drilling, or crushing operations.
Implementation Method 1
the cobalt in the cemented carbide body plays a vital role in the sense that is responsible for the generation of heat through the induction of an eddy current therein
Implementation Method 2
the solder is melted and then forced to diffuse into the cemented carbide body and into the steel by means of inductive heating thereof
Implementation Method 3
said compound and said grain growth promoting element is of a type that will diffuse into the compact in connection to sintering of the latter and thereby will induce a generation of a cobalt content gradient
Implementation Method 4
sintering the compact provided with said compound and said grain growth promoting element into said cemented carbide body
Data Source
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AI summary
A tool (1) for cutting, drilling or crushing of solid material, wherein -said tool (1) comprises a cemented carbide body (2) attached to a steel holder (3) by a braze joint located between a base surface (8) of the cemented carbide body (2) and the steel holder (3), -said cemented carbide body (2) comprises a hard phase mainly comprised by tungsten carbide, WC, and a binder consisting of cobalt, wherein the cobalt content of the cemented carbide body (2) is equal to or lower than about 5.5 wt%, and wherein, - the cemented carbide body (2) presents a cobalt content gradient therein wherein the cobalt content increases towards said base surface (8) and is at least 4.5 wt% at said base surface (8), - the ratio cobalt content at the base surface to cobalt content of the cemented carbide is ≥ 1.09. A method for producing the tool is also presented.