Cermets Cutting Tool Residual Stress Distribution
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Solution Overview
Problem
Existing cutting tools made of cermet materials face challenges in achieving high toughness and minimizing deformation during firing, leading to issues with working accuracy and chipping resistance, especially when producing complex shapes with multiple corner cutting edges.
Innovation Solution
A cutting tool with a sintered cermet body composed of two types of hard phases and a binding phase, where residual stresses are applied differently to each phase, increasing the hardness and binding force, thereby improving toughness and suppressing crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If residual stress is generated by setting the surface portion and interior portion to have different binding phase contents, then chipping resistance is improved, but the content ratio of binding phase is low resulting in insufficient residual stress and poor toughness
Solution Approach 1:
The patent applies different binding phase contents to different regions (surface vs interior) of the cermet. The surface portion has lower binding phase content (0.5-5 mass%) to generate compressive residual stress for chipping resistance, while the interior has higher binding phase content (5-15 mass%) to ensure sufficient residual stress and toughness. This local differentiation resolves the contradiction between surface hardness and overall toughness.
Solution Approach 2:
The patent changes the binding phase content parameter across different regions of the cermet. By controlling the binding phase content to decrease from the interior toward the surface, the patent achieves both sufficient residual stress in the interior (for toughness) and appropriate surface properties (for chipping resistance), resolving the contradiction through parameter gradient design.
2Strength
If residual stress is applied uniformly to the hard phase, then the method is simple, but the strength of the hard phase is limited and cannot be sufficiently improved
Solution Approach 1:
Instead of uniform residual stress application, the patent creates a localized stress distribution where the interior portion generates compressive residual stress (50-200 MPa) through higher binding phase content, while the surface portion has different properties. This localized approach allows the hard phase in the interior to achieve sufficient strength while maintaining manufacturing feasibility.
3Strength
If the cermet structure is designed to improve chipping resistance, then crack propagation is suppressed, but the cermet has large deformation due to firing resulting in poor working accuracy
Solution Approach 1:
The patent localizes the binding phase content variation to specific regions, with the interior having higher content to suppress crack propagation and improve chipping resistance, while the surface has lower content to minimize firing deformation. This regional differentiation allows the material to achieve both high chipping resistance and acceptable working accuracy.
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 approach enhances the toughness and chipping resistance of the cutting tool, reducing deformation during firing and ensuring high working accuracy, particularly for complex shapes with multiple corner cutting edges.
Implementation Method 1
when residual stresses are measured by a 2D method, a residual stress σ11[1i] in a direction σ11 of the first hard phase is 80 MPa or more in terms of compressive stress (σ11[1i] ≤ -80 MPa), a residual stress σ11[2i] in the direction σ11 of the second hard phase is -50 MPa to 50 MPa in terms of compressive or tensile stress (σ11[2i] = -50 MPa to 50 MPa)
Data Source
Figure 1(a)~2
AI summary
To provide a cutting tool which is formed from a cermet sintered body that is reduced in deformation due to firing and has high strength. [Solution] A cutting tool (1) which is composed of a cermet sintered body (6) that is configured of a hard phase (11) which is composed of two kinds of hard phases, namely a first hard phase (12) and a second hard phase (13), and a binder phase (14) that is composed of Co and/or Ni. At a depth of 400 µm or more from the rake face (2)-side surface of the cermet sintered body (6), the residual stress σ11[1i] in the σ11 direction of the first hard phase (12) is a compressive stress of 80 MPa or more (σ11[1i] ≤ -80 MPa), the residual stress σ11[2i] in the σ11 direction of the second hard phase (13) is a compressive or tensile stress of from -50 MPa to 50 MPa (σ11[2i] = -50 MPa to 50 MPa), and the residual stress σ11[bi] in the σ11 direction of the binder phase (14) is a compressive or tensile stress of from -50 MPa to 50 MPa (σ11[bi] = -50 MPa to 50 MPa) as determined by a 2D method.