Cemented Carbide Body Joining to Prevent Sintering Cracks
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Solution Overview
Problem
The manufacturing of cemented carbide bodies, particularly cutting members, often results in cracks due to differential shrinkage during sintering, especially when complex geometries are involved, leading to reduced product quality and increased costs.
Innovation Solution
A method involving the mechanical joining of fully sintered parts with plane and parallel surfaces, using a metal foil for improved bonding, and heat treatment within a specific temperature range to prevent additional shrinkage and ensure a strong, void-free joint, allowing for the use of different compositions and grain sizes in various parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If multiple parts are pressed and sintered together to form complex geometry cemented carbide bodies, then the manufacturing capability for complex shapes is improved, but cracks occur due to differential shrinkage during sintering
Solution Approach 1:
The cemented carbide body is divided into multiple separate parts that are pressed and sintered individually to full density before being mechanically joined together. This segmentation allows each part to be manufactured independently without differential shrinkage issues, while still achieving complex overall geometry through assembly of multiple fully-dense components.
Solution Approach 2:
The parts are pressed to green bodies and sintered to full density before the final assembly operation. This preliminary completion of densification eliminates subsequent shrinkage that would cause cracks during or after joining, ensuring structural integrity of the assembled complex geometry body.
2Ease of manufacture
If parts are pressed to green bodies and then sintered together, then manufacturing flexibility is improved, but differential shrinkage causes cracks in the cemented carbide body
Solution Approach 1:
Each part is sintered to full density individually before assembly, completing the dimensional stabilization process beforehand. This eliminates unpredictable shrinkage during final assembly, ensuring precise dimensional control of the finished complex geometry body while retaining manufacturing flexibility.
Solution Approach 2:
The sintering process parameters are optimized to achieve full density transformation in each part before assembly. By controlling the sintering parameters to complete densification beforehand, the method achieves both manufacturing flexibility and precise dimensional control without crack formation.
3Shape
If injection moulding is used for large cemented carbide bodies, then complex geometry manufacturing is improved, but cracks form during sintering following injection moulding
Solution Approach 1:
The large complex geometry body is divided into multiple smaller parts suitable for injection moulding, each of which is sintered individually to full density before assembly. This segmentation prevents crack formation that would occur in large single-piece injection moulded bodies while maintaining the ability to manufacture complex geometries.
Solution Approach 2:
Each injection moulded part is sintered to full density immediately after moulding, completing the densification process before assembly. This preliminary action eliminates subsequent shrinkage and crack formation, ensuring reliability of the final assembled large complex geometry body.
4Manufacturing precision
If machining is performed on sintered bodies to achieve desired shape, then geometric precision is improved, but manufacturing cost increases
Solution Approach 1:
The parts are pressed to green bodies with the desired final geometry before sintering, achieving near-net-shape formation. This preliminary shaping eliminates or minimizes subsequent machining operations on the sintered body, reducing manufacturing cost while maintaining geometric precision through controlled pressing and sintering processes.
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 prevents cracks and ensures a strong, void-free bond between parts, maintaining the final shape and quality of the cemented carbide body, reducing machining needs and enhancing the manufacturing efficiency and cost-effectiveness.
Implementation Method 1
The binder phase usually comprises cobalt (Co) as a main constituent... The obtained slurry is then dried and granulated... sintering of the parts
Implementation Method 2
During sintering the body normally shrinks about 17% linearly... During sintering of a powder injection moulded part the part normally shrinks about 20% linearly
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for manufacturing a cemented carbide body (1), comprising the following steps: - forming a first part (2, 9, 14, 17) of a first powder composition comprising a first carbide and a first binder phase, - sintering the first part (2) to full density in a first sintering operation, - forming a second part (3) of a second powder composition comprising a second carbide and a second binder phase, - sintering the second part (3) to full density in a second sintering operation, - bringing a first surface (4) of the first part (2) and a second surface (5) of the second part (3) in contact, and - joining the first and second surface in a heat treatment operation.