Sintered Hard Metal Granules with Surface Binder Enrichment
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Solution Overview
Problem
Existing methods for producing hard metal components via additive manufacturing, such as 3D binder printing, face limitations in achieving high green density and strength due to low bulk density of commercial hard metal powders/granules and the need for high binder metal content, which can lead to component disintegration during sintering.
Innovation Solution
A method involving the mixing and granulation of hard materials with binder metal, followed by a controlled cooling rate or surface coating with binder metal using PVD/PECVD, creating an inhomogeneous distribution where the binder metal concentration is significantly higher on the surface than inside the granules, enabling improved sintering at lower temperatures and enhanced green and sintered densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional commercial hard metal powders/granules are used with low binder metal content (≤19 vol.%), then component disintegration during sintering is avoided, but green body density and strength are insufficient for additive manufacturing
Solution Approach 1:
The patent applies local quality by creating an inhomogeneous distribution of binder metal within granules, with higher concentration at the surface (at least 25% greater than interior). This allows the surface to provide sufficient binding strength during sintering while the interior maintains lower binder content to prevent disintegration, resolving the contradiction between green body density and component stability.
Solution Approach 2:
The patent creates composite granules with heterogeneous binder metal distribution, combining regions of high binder content (surface) and low binder content (interior) within a single granule. This composite structure enables the granule to simultaneously achieve high green body density from surface binding and structural stability from low interior binder content during sintering.
2Quantity of substance
If high binder metal content is used to achieve high green body density, then additive manufacturing becomes feasible, but component disintegration occurs during sintering due to excessive binder removal
Solution Approach 1:
The patent applies local quality by creating an inhomogeneous distribution of binder metal within granules, with higher concentration at the surface (at least 25% greater than interior). This allows the surface to provide sufficient binding strength during sintering while the interior maintains lower binder content to prevent disintegration, resolving the contradiction between green body density and component stability.
Solution Approach 2:
The patent creates composite granules with heterogeneous binder metal distribution, combining regions of high binder content (surface) and low binder content (interior) within a single granule. This composite structure enables the granule to simultaneously achieve high green body density from surface binding and structural stability from low interior binder content during sintering.
3Quantity of substance
If laser sintering with very high temperatures is applied to sinter pre-sintered hard metal granules, then compaction is achieved, but decomposition of tungsten carbide and formation of undesirable eta phase occur
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate through the three-phase range (WC, Co-liquid, C-solid) during sintering. This controlled cooling enables compaction and densification at lower temperatures, avoiding the very high temperatures that cause tungsten carbide decomposition and eta phase formation, thus resolving the contradiction between green body density and material 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
This approach allows for the production of hard metal components with high green and sintered density and strength, enabling geometric complexity and stability while reducing the risk of decomposition and undesirable phase formation during processing.
Implementation Method 1
sintering of the hard metal granules and controlling the cooling rate in the three-phase range WC, Co-liquid and C-solid
Implementation Method 2
coating of the hard materials with binding metal by means of physical vapor deposition
Implementation Method 3
coating of the hard materials with binding metal by means of physical vapor deposition/plasma-enhanced chemical vapor deposition (PVD/PECVD)
Implementation Method 4
sintering of the hard metal granules
Data Source
AI summary
The invention relates to the fields of cemented carbide materials and ceramic and/or powder metallurgical process engineering and concerns a sintered cemented carbide granulate, such as can be used, for example, for the production of wear parts or tools with cemented carbides, and its use. The object of the present invention is to provide a cemented carbide granulate with which cemented carbide green bodies and sintered bodies can be produced that exhibit high green density and high green strength, and to specify their use. This object is achieved by sintered cemented carbide granulate which, in the majority of granules, has an inhomogeneous distribution of hard material and binder metal within the individual granule, wherein the concentration of the binder metal on the surface of the individual granule is, on the whole, at least 25% higher than in the interior of the granule.