Cemented Carbide Composition for Stable Coating Adhesion in Cutting Tools
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Solution Overview
Problem
Conventional cemented carbides used in cutting tools experience premature coating film peeling and reduced tool life when processing cemented carbides due to inhomogeneous coating film structures.
Innovation Solution
A cemented carbide composition comprising specific grain size distributions and volume percentages of tungsten carbide, second hard phases, and a binder phase, along with controlled distances and variations between second hard phase centroids, enhances the homogeneity of the coating film, improving tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on conventional cemented carbide, then the cutting tool can process cemented carbides, but the coating film peels off prematurely due to inhomogeneous coating structure
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of second hard phases (TiCN, TaNbC, etc.) within the cemented carbide substrate. These phases are strategically positioned to form a transition layer that gradually changes composition and structure from the substrate to the coating surface, providing localized structural optimization that prevents coating peeling while extending tool life.
Solution Approach 2:
The patent employs composite materials by combining multiple phases (tungsten carbide as first hard phase, TiCN/TaNbC as second hard phases, and cobalt binder phase) with specific volume ratios. This multi-phase composite structure creates a gradient composition that improves coating adhesion and overall tool performance when processing cemented carbides.
2Manufacturing precision
If the grain size of tungsten carbide is increased to improve coating homogeneity, then coating film uniformity improves, but the cemented carbide loses its cutting edge sharpness
Solution Approach 1:
The patent applies parameter changes by optimizing the grain size distribution of tungsten carbide within specific ranges (D10: 0.40-2.00 μm, D50: 0.60-1.50 μm, D90: 1.00-3.00 μm). These controlled parameter variations achieve the right balance between coating homogeneity and cutting edge sharpness, preventing both coating defects and edge deterioration.
Solution Approach 2:
The patent uses local quality by implementing a specific grain size distribution where finer grains (D10) provide coating uniformity while coarser grains (D90) maintain edge strength. This localized grain size optimization throughout the material structure resolves the contradiction between coating homogeneity and cutting performance.
3Reliability
If the content of second hard phases is increased to improve coating adhesion, then coating film stability improves, but the hardness of the cemented carbide decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the volume content of second hard phases within 0.30-1.60%. This optimized parameter range ensures sufficient coating adhesion and stability while maintaining the hardness and overall strength of the cemented carbide substrate for effective cutting operations.
Solution Approach 2:
The patent uses composite materials by combining second hard phases (TiCN, TaNbC) with specific properties that provide both coating adhesion and substrate hardness. The multi-phase composite structure allows simultaneous achievement of coating stability and material strength through synergistic phase interactions.
Data Source
AI summary
A cemented carbide consisting of a first hard phase, second hard phases, and a binder phase, wherein the first hard phase is composed of tungsten carbide grains, a D10 and a D90 of grain sizes of the tungsten carbide grains are 0.40 μm and 2.00 μm respectively, the second hard phases are composed of at least one first compound selected from the group consisting of TaNbC, TaNbN, TaNbCN, TiCN, TiNbC, TiNbN, and TiNbCN, the cemented carbide includes 0.30% to 1.60% by volume of the second hard phases, a median of a distance between centroids of two of the second hard phases that are closest is 4 to 15 μm, a coefficient of variation of the distance between centroids is 1.20 to 1.90, the binder phase includes 50% by mass or more of cobalt, and the cemented carbide includes 8.0 to 14.0% by volume of the binder phase.