CBN Coated Cutting Tool Structure for Stronger Coating Adhesion
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Solution Overview
Problem
Conventional coated cutting tools experience insufficient adhesion between the coating layer and substrate, leading to peeling and reduced fracture resistance, resulting in short tool life when machining hardened steel and heat-resistant alloys.
Innovation Solution
A coated cutting tool with a substrate made of a cubic boron nitride-containing sintered body and a coating layer comprising specific layer compositions and structures, including a lower layer with a composition of (Ti 1-x Al x )N and an upper layer of (Ti 1-y Al y )(C 1-z N z), optimized for improved adhesion and fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a coating layer is formed on a cubic boron nitride substrate to improve machining efficiency, then cutting performance is enhanced, but adhesion between the coating layer and substrate becomes insufficient, leading to peeling and reduced fracture resistance
Solution Approach 1:
The coating layer is divided into multiple layers with different compositions and functions: a lower part layer (Ti,Al)N with fine particles for strong substrate adhesion, intermediate layers for transition, and an upper part layer for cutting performance. This segmentation allows each layer to optimize for its specific function, resolving the adhesion problem while maintaining machining efficiency.
Solution Approach 2:
The patent uses composite material structures both in the substrate (cubic boron nitride particles with binder phase) and in the coating layer (multiple layers with different Ti-Al compositions and particle sizes). The composite structure enables simultaneous achievement of hardness, adhesion, and fracture resistance, overcoming the limitation of single-material coatings.
2Ease of manufacture
If the particle size of the lower part layer is large to simplify manufacturing, then production is easier, but adhesion becomes insufficient, leading to peeling and short tool life
Solution Approach 1:
Different particle sizes are used in different layers of the coating: fine particles (0.01-0.05 μm) in the lower part layer for maximum adhesion to the substrate, while coarser particles may be used in upper layers where adhesion is less critical. This local optimization of particle size achieves both good adhesion and manufacturability.
Solution Approach 2:
The patent systematically varies particle size parameters across different layers: the lower part layer uses the finest particles (0.01-0.05 μm) for adhesion, while other layers may use progressively larger particles. This parameter gradient allows optimization of both adhesion and manufacturing characteristics without compromising tool life.
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 tool exhibits enhanced fracture resistance and wear resistance, leading to a longer tool life and improved machining performance for hardened steel and heat-resistant alloys.
Implementation Method 1
a coating layer is formed by vapor deposition
Data Source
Figure 1
AI summary
A coated cutting tool, comprising: a substrate made of a cubic boron nitride-containing sintered body; and a coating layer formed on the substrate, wherein the cubic boron nitride-containing sintered body includes 65 volume% or more and 85 volume% or less of cubic boron nitride, and 15 volume% or more and 35 volume% or less of a binder phase; the cubic boron nitride is in a form of particles, the particles having an average particle size from 1.5 µm or more to 4.0 µm or less; the coating layer includes a lower layer, and an upper layer formed on the lower layer; the lower layer contains particles each having a composition represented by (Ti1-xAlx)N; the lower layer has an average thickness from 0.1 µm or more to 1.0 µm or less; the particles forming the lower layer have an average particle size from 0.01 µm or more to 0.05 µm or less; the upper layer contains particles each having a composition represented by (Ti1-yAly)(C1-zNz); and the upper layer has an average thickness from 1.0 µm or more to 5.0 µm or less.