AlTiCN Coating Structure for Thermal Crack-Resistant Cutting Tools
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Solution Overview
Problem
Conventional cutting tools with AlTiCN layers experience thermal cracking and wear on the rake and flank faces during wet processing of gray cast iron, leading to reduced tool life.
Innovation Solution
A cutting tool with a coated film featuring a first layer composed of Al x Ti 1-x C y N 1-y crystal grains, where x is between 0.65 and 0.95 and y is between 0 and 0.1, with specific aspect ratios and a high percentage of cubic crystal structure, providing enhanced thermal cracking and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional AlTiCN coating layer is used on the cutting tool, then wear resistance is improved, but thermal cracking resistance deteriorates during wet processing of gray cast iron
Solution Approach 1:
The coating is divided into two distinct layers with different compositions and properties: a first layer (Al x Ti 1-x C y N 1-y with x=0.65-0.95, y=0-0.1) providing wear resistance, and a second layer (Al u Ti 1-u C v N 1-v with u=0.30-0.70, v=0.05-0.20) providing thermal cracking resistance. Each layer is optimized locally for its specific function, resolving the contradiction between wear resistance and thermal cracking resistance.
Solution Approach 2:
The invention uses a composite coating structure consisting of two different Al-Ti-C-N coating layers with distinct compositional ranges and microstructural characteristics. The first layer has higher Al content and lower C content for wear resistance, while the second layer has lower Al content and higher C content for thermal cracking resistance, creating a composite material system that combines both properties.
2Duration of action of moving object
If the coating layer thickness is increased to improve wear resistance, then tool life is extended, but the complexity of coating formation increases
Solution Approach 1:
The coating is segmented into two functional layers with distinct compositions and thicknesses. The first layer (2-20 μm) provides wear resistance while the second layer (2-10 μm) provides thermal cracking resistance. This segmentation allows each layer to be optimized for its specific function without requiring excessive total thickness, thereby extending tool life while controlling structural complexity.
Data Source
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AI summary
A cutting tool includes a substrate and a coated film arranged on the substrate. The coated film includes a first layer. The first layer includes a plurality of crystal grains. The crystal grains are composed of AlxTi1-xCyN1-y, wherein x is more than 0.65 and less than 0.95, and y is not less than 0 and less than 0.1. In a first region, the crystal grains have an average aspect ratio of not more than 3.0, where the first region is a region that is sandwiched between a surface S1 of the first layer or an interface S2 on a surface side of the first layer and a first virtual plane VS1. In a second region, the crystal grains have an average aspect ratio of more than 3.0 and not more than 10.0, where the second region is a region that is sandwiched between the first virtual plane VS1 and an interface S3 on a substrate side of the first layer. The first virtual plane VS1 passes through a point that is 1 µm away from the surface S1 or the interface S2 on the substrate side, and is parallel to the surface S1 or the interface S2. The crystal grains include crystal grains having a cubic crystal structure. The first layer has a ratio of an area occupied by the crystal grains having a cubic crystal structure of not less than 90%. The average aspect ratios and the area ratio are measured on a cross section along a normal to an interface between the substrate and the coated film. The first layer has a thickness of not less than 2 µm and not more than 20 µm.