Layered Coated Cutting Tool for Heat-Resistant Wear Protection
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Solution Overview
Problem
Conventional coated cutting tools with AlTi-based nitrides or carbonitrides face limitations in durability due to the presence of brittle AlN with a hexagonal closest packed structure, which affects hardness and wear resistance.
Innovation Solution
A coated cutting tool design featuring a layered coating film structure with specific composition ranges for Al, Ti, Cr, and Si, where Al-rich AlCrN-based and AlTiN-based layers are alternately layered, reducing the amount of AlN with a hexagonal closest packed structure, and an AlTi-based nitride or carbonitride in the upper layer, enhancing adhesion and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the Al content in the nitride of Al and Ti is increased to enhance heat resistance, then heat resistance is improved, but AlN with a brittle hcp structure precipitates and hardness decreases
Solution Approach 1:
The coating film is divided into multiple layers with different compositions and functions. The first layer (AlTiN-based) provides heat resistance, the second layer (AlCrN-based) provides hardness and wear resistance, and the third layer (AlTiN-based) provides toughness. This segmentation allows each layer to optimize its properties without the drawbacks of high-Al content in a single layer.
Solution Approach 2:
The invention uses a composite coating structure combining different nitride materials (AlTiN and AlCrN) in specific layers. This composite approach allows the coating to simultaneously achieve heat resistance from AlTiN, hardness from AlCrN, and improved toughness through the layered composite structure, avoiding the brittleness of high-Al content single-layer coatings.
2Ease of operation
If a hard coating film containing AlN with high Al content and hcp structure is provided to improve lubricity and welding resistance, then lubricity and welding resistance are improved, but durability decreases due to the brittle hcp structure
Solution Approach 1:
Different layers are designed with different compositions and properties tailored to specific functional requirements. The AlCrN-based layer provides lubricity and welding resistance where needed, while the AlTiN-based layers provide heat resistance and toughness in regions where these properties are prioritized. This local optimization allows the coating to achieve multiple properties without the brittleness penalty throughout the entire structure.
Solution Approach 2:
The layered composite structure combines AlTiN and AlCrN nitrides, where the AlCrN layer specifically addresses lubricity and welding resistance needs, while the overall composite structure maintains durability through the toughness-providing AlTiN layers and the intermediate adhesion layer design.
3Temperature
If the content percentage of Al is increased to 70% to enhance heat resistance, then heat resistance is further enhanced, but the hcp structure is confirmed and hardness begins to decrease
Solution Approach 1:
Instead of using a single layer with 70% Al content, the invention segments the coating into multiple layers with different Al content ranges. The AlTiN-based layers contain 60-80 at% Al for heat resistance, while the AlCrN-based layer contains 50-70 at% Al for hardness, avoiding the hcp structure precipitation that occurs at uniformly high Al content.
Solution Approach 2:
The invention changes the compositional parameters across different layers, specifically controlling Al content to be 60-80 at% in AlTiN-based layers and 50-70 at% in AlCrN-based layers. This parameter optimization prevents the formation of brittle hcp AlN structure while maintaining heat resistance and hardness properties.
Data Source
AI summary
Provided is a coated cutting tool, which includes a hard coating film containing a layer (b) formed of a nitride or a carbonitride, a layer (c) which is a layered coating film formed by alternately layering a nitride or carbonitride layer (c1) that contains 55 atom % or more and 75 atom % or less of Al, Cr having a second highest content percentage, and at least Si and a nitride or carbonitride layer (c2) that contains 55 atom % or more and 75 atom % or less of Al and Ti having a second highest content, and a layer (d) that is a nitride or carbonitride that contains, with respect to a total amount of metal elements (including metalloid elements), 55 atom % or more and 75 atom % or less of Al and Ti having a second highest content percentage, the content percentage of Ti being 20 atom % or more.