CBN Cutting Tool Coating for Adhesion and Wear Resistance
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Solution Overview
Problem
Conventional coated cutting tools experience insufficient adhesion of the coating layer to the substrate under severe cutting conditions, leading to peeling and fractures, particularly when machining hard-to-cut materials like quenched steel and heat-resistant alloys, resulting in reduced tool life.
Innovation Solution
A coated cutting tool with a substrate of cubic boron nitride sintered body and a coating layer comprising a Ti carbonitride layer with specific atomic ratios, thickness, and texture coefficients, along with a lower layer, to enhance adhesion and fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional coating layer is formed on the cubic boron nitride substrate, then wear resistance is improved, but adhesion under severe cutting conditions deteriorates leading to peeling and fractures
Solution Approach 1:
The coating layer is divided into multiple functional layers: a lower layer (TiAlN or TiN) providing gradient adhesion to the substrate, and an upper layer (Ti carbonitride) providing wear resistance. This segmentation allows each layer to optimize its specific function while maintaining overall system reliability.
Solution Approach 2:
The invention uses composite material structures where Ti carbonitride (Ti(CxN1-x)) is combined with TiAlN or TiN layers. The composite structure leverages the high hardness and wear resistance of Ti carbonitride while the TiAlN/TiN lower layer provides excellent adhesion to the cubic boron nitride substrate, resolving the contradiction between wear resistance and adhesion.
2Productivity
If cutting speed and feed are increased to improve productivity, then machining efficiency is improved, but fracture resistance deteriorates due to insufficient adhesion
Solution Approach 1:
The lower layer of TiAlN or TiN is applied first to the cubic boron nitride substrate before applying the Ti carbonitride upper layer. This preliminary action creates a strong adhesive foundation that prevents coating peeling under high-speed cutting conditions, thereby enabling higher productivity without sacrificing fracture resistance.
3Duration of action of moving object
If the coating layer thickness is increased to improve wear resistance, then tool life is extended, but adhesion deteriorates causing peeling
Solution Approach 1:
Instead of using a single thick coating layer, the invention segments the coating into a thinner lower layer (TiAlN or TiN) and an upper layer (Ti carbonitride). This segmentation maintains adhesion quality while achieving sufficient wear resistance through the combined thickness and properties of both layers, preventing peeling even when total coating thickness is increased.
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 solution significantly improves wear resistance and fracture resistance, extending the tool life by ensuring better adhesion between the substrate and coating layer, reducing peeling, and enhancing the tool's ability to handle high-speed cutting of hard materials.
Implementation Method 1
in the Ti carbonitride layer, a texture coefficient TC (111) of a (111) plane represented by a following formula (1) is 1.0 or more and 2.0 or less
Implementation Method 2
in X-ray diffraction measurement of the Ti carbonitride layer, an absolute value of a difference between a maximum value and a minimum value of 2θ represented by a following formula (2) is 0.1° or less on the (111) plane
Implementation Method 3
the adhesion between the substrate and the coating layer is improved, thereby making it possible to improve the fracture resistance
Implementation Method 4
a coating layer consisting of a lower layer consisting of a composite nitride layer of titanium and aluminum, a first intermediate layer consisting of a titanium nitride layer, a second intermediate layer consisting of a titanium carbonitride layer, and an upper layer consisting of a titanium nitride layer is formed by vapor deposition on a surface of a substrate
Data Source
AI summary
A coated cutting tool comprising a substrate comprising a cubic boron nitride sintered body and a coating layer formed on the substrate, wherein the coating layer comprises a Ti carbonitride layer comprising Ti(CxN1-x); an average thickness of the Ti carbonitride layer is 0.5 μm or more and 5.0 μm or less; in the Ti carbonitride layer, R75 is higher than R25; in the Ti carbonitride layer, a texture coefficient TC (111) of a (111) plane is 1.0 or more and 2.0 or less; and in X-ray diffraction measurement of the Ti carbonitride layer, an absolute value of a difference between a maximum value and a minimum value of 2θ is 0.1° or less on the (111) plane when the measurement is performed at each of ψ angles of 0°, 30°, 50° and 70°.