Indexable Cutting Tool Gradient Structure for Wear and Welding Resistance
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Solution Overview
Problem
Indexable cutting tools face challenges in wear resistance, fracture resistance, and welding resistance, particularly when cutting low-carbon steel, where the binder phase layer reacts with iron, leading to fractures, and the mounting portion experiences chipping or plastic deformation due to strong stress, causing wobbling and roughness on the workpiece.
Innovation Solution
The indexable cutting tool features a cermet composition with 75-95% hard phase and a binder phase, including a layer structure A (binder phase), structure B (TiCN and binder phase), and structure C (hard phase and binder phase), with structure C forming the cutting edge to prevent welding and wear, and structure A and B in the mounting hole to absorb impacts and maintain toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a binder phase layer is formed on the surface of a cermet cutting tool to improve wear resistance and fracture resistance, then the surface roughness is improved and wear/fracture resistance increases, but the binder phase layer reacts with iron in low-carbon steel during cutting, leading to welding fractures and rough finish surfaces
Solution Approach 1:
The invention applies different structural characteristics to different regions of the cutting tool. The surface layer (0-5μm from cutting edge) has high hardness (18-22 GPa) and low binder phase content to prevent welding reactions, while the inner region maintains higher toughness with more binder phase. This local differentiation allows the surface to resist wear and welding while the interior provides fracture resistance.
Solution Approach 2:
The cutting tool employs a composite cermet structure combining WC (tungsten carbide) and TiCN (titanium carbonitride) hard phases with iron group metal binder phase. This composite material system provides both hardness for wear resistance and controlled reactivity to prevent welding, achieving a balance between surface performance and chemical stability.
2Strength
If the mounting portion of the cutting tool is strengthened to resist strong stress during intermittent cutting, then fracture resistance improves, but the mounting portion becomes prone to plastic deformation and chipping under severe stress conditions
Solution Approach 1:
The invention creates a gradient structure where the mounting portion (inner region beyond 5μm from cutting edge) has optimized composition and structure with sufficient binder phase content to provide toughness and ductility. This local structural optimization allows the mounting portion to absorb impact stresses and resist chipping while maintaining overall fracture resistance.
3Reliability
If the cutting edge is made harder to improve wear resistance, then wear resistance increases, but the cutting edge becomes more susceptible to chipping and fractures due to reduced toughness
Solution Approach 1:
The invention implements a depth-dependent structural gradient where the cutting edge surface (0-5μm) has high hardness (18-22 GPa) for wear resistance, while the underlying regions have progressively higher toughness. This local differentiation ensures the cutting edge resists wear without sacrificing the toughness needed to prevent chipping and fractures.
Solution Approach 2:
The composite cermet structure with WC and TiCN hard phases provides exceptional wear resistance at the cutting edge, while the iron group metal binder phase maintains adequate toughness. The synergistic combination of these materials allows the cutting edge to simultaneously achieve high hardness and sufficient fracture resistance.
Data Source
Figure 1A~1B
Figure 2
AI summary
An indexable cutting tool 100 includes a cermet including 75 to 95 mass% a hard phase and a balance of a binder phase and inevitable impurities, the binder phase containing an iron group metal. The cutting tool 100 includes a layer of a structure A and a layer of a structure B extending from an inner peripheral face 5r of a mounting hole 5 toward the inside of the cutting tool, and further includes a structure C within the cutting tool beyond the layer of the structure B. An outermost surface portion of a cutting edge section 4r of the insert 100 is composed of the structure C. The structure A is substantially composed of the binder phase, the structure B is composed of TiCN and the binder phase, and the structure C is composed of the hard phase and the binder phase.