Cemented Carbide Cutting Tool Coating Adhesion
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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, leading to improved tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hard film is formed on a conventional cemented carbide base body, then the cutting tool has improved wear resistance, but the coating film peels off prematurely and tool life is reduced
Solution Approach 1:
The patent applies local quality by introducing second hard phases (TaNbC, TaNbN, TaNbCN, TiCN, TiNbC, TiNbN, or TiNbCN) at specific locations and concentrations (0.30-1.60% by volume) within the cemented carbide base body. These localized regions with controlled properties (median distance between centroids of 4-15 μm, coefficient of variation of 1.20-1.90) create optimal bonding interfaces that prevent coating peeling while extending tool life.
2Strength
If the grain size of tungsten carbide is increased to improve toughness, then the material becomes more resistant to chipping, but the coating film homogeneity deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the grain size distribution of tungsten carbide (D10 ≥ 0.40 μm, D90 ≤ 2.00 μm) and the spatial distribution parameters of second hard phases (median distance 4-15 μm, coefficient of variation 1.20-1.90). These controlled parameter ranges simultaneously achieve improved toughness through adequate grain size while maintaining coating homogeneity through optimized phase distribution.
3Reliability
If the content of second hard phases is increased to improve abrasion resistance, then the cutting edge becomes more wear-resistant, but the coating film becomes more inhomogeneous
Solution Approach 1:
The patent resolves this contradiction by optimizing the concentration and spatial distribution parameters of second hard phases. By limiting the volume content to 0.30-1.60% and controlling the median distance between centroids to 4-15 μm with a coefficient of variation of 1.20-1.90, the invention achieves improved abrasion resistance while preventing coating inhomogeneity that would occur with higher or more clustered concentrations.
Data Source
Figure 1
Figure 2~3
AI summary
A cemented carbide consisting of a first hard phase, a plurality of second hard phases, and a binder phase, wherein the first hard phase is composed of a plurality of tungsten carbide grains, a D10 of grain sizes of the tungsten carbide grains is 0.40 µm or more, a D90 of grain sizes of the tungsten carbide grains is 2.00 µm or less, 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% by volume or more and 1.60% by volume or less of the second hard phases, in a cross section of the cemented carbide, a median of a distance between centroids of two of the second hard phases that are closest is 4 µm or more and 15 µm or less, a coefficient of variation of the distance between centroids is 1.20 or more and 1.90 or less, the binder phase includes 50% by mass or more of cobalt, and the cemented carbide includes 8.0% by volume or more and 14.0% by volume or less of the binder phase.