Coated Cutting Tool Laminate for Stronger Coating Adhesion
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Solution Overview
Problem
Existing coated tools face challenges in improving the adhesion between the coating film and the base body, which affects the durability and longevity of the tool.
Innovation Solution
A coated tool design featuring a metal layer with high adhesion to the base body, sandwiched between the base body and a hard layer, enhances the bonding between the coating film and the base body, using an arc ion plating method to form a laminate structure with alternating metal nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is applied to improve wear resistance, then the tool durability is improved, but the adhesion between the coating film and base body deteriorates
Solution Approach 1:
The patent applies a multi-layer composite coating structure consisting of a base body, intermediate layer, and coating film. The intermediate layer acts as a transition zone between the base body and the coating film, improving interfacial adhesion. This composite structure resolves the contradiction by combining materials with different properties: the base body provides structural support, the intermediate layer enhances bonding, and the coating film provides wear resistance, thereby achieving both high adhesion and tool durability simultaneously
Solution Approach 2:
The intermediate layer serves as an intermediary between the base body and the coating film. This intermediate layer is specifically designed to improve the bonding interface, acting as a mediator that transfers and distributes stresses between the dissimilar materials. By introducing this intermediate layer, the patent successfully improves adhesion without compromising the wear resistance provided by the outer coating film
2Reliability
If the coating film is made harder to improve wear resistance, then the tool life is extended, but the coating film becomes more prone to peeling and cracking
Solution Approach 1:
The patent employs parameter changes by creating a gradient in material properties through the intermediate layer. The intermediate layer has transitional mechanical properties between the ductile base body and the hard coating film, with its hardness, elasticity, and thermal expansion coefficients gradually changing from the base body side toward the coating film side. This gradual parameter transition prevents sudden stress concentration, allowing the coating film to maintain high hardness for wear resistance while reducing peeling and cracking through the buffering effect of the intermediate layer
Solution Approach 2:
The multi-layer composite structure allows combining a hard outer coating film for wear resistance with a more ductile intermediate layer and base body for toughness. The composite structure distributes mechanical stresses across different layers, preventing stress concentration at a single interface. This resolves the contradiction by enabling the coating film to be hard enough for extended tool life while the intermediate layer maintains structural integrity and prevents peeling and cracking
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 improved adhesion leads to higher durability and extended tool life by reducing peeling and cracking, with the metal layer providing enhanced wear and heat resistance, and the laminate structure maintaining mechanical properties.
Implementation Method 1
using an arc ion plating method to form a laminate structure with alternating metal nitride layers
Data Source
AI summary
A coated tool according to the present disclosure comprises a base body and a coating film. The base body is made of a cemented carbide or a cermet. The coating film is located on the base body. In a case where a hardness is measured by pressing an indenter from a surface of the coating film to a depth of 20% of the coating film while changing an indentation load of the indenter, when a minimum hardness of the hardness is defined as a first hardness, a maximum hardness of the hardness is defined as a second hardness, a depth at the first hardness is defined as a first hardness depth, and a depth at the second hardness is defined as a second hardness depth, the second hardness depth is smaller than the first hardness depth, and a difference therebetween is greater than 7 GPa.