cBN Cutting Tool Coating for Wear and Chipping Resistance
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Solution Overview
Problem
Existing surface-coated cutting tools lack compatibility between reduced chipping and excellent wear resistance, particularly in intermittent cutting of high-hardness steel, leading to short tool service lives.
Innovation Solution
A surface-coated cutting tool with a hard coating layer comprising a lower AlTiN sublayer and an upper AlTiBN sublayer, featuring a compositionally variable profile for the B component, which enhances hardness, thermal conductivity, and toughness, thereby reducing chipping and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is formed on cemented carbide or cBN substrate, then wear resistance is improved, but chipping resistance deteriorates in intermittent cutting of high-hardness steel
Solution Approach 1:
The hard coating layer is divided into multiple sublayers (first sublayer, second sublayer, and third sublayer) with different compositions and functions. The first sublayer provides adhesion to the substrate, the second sublayer provides hardness and wear resistance, and the third sublayer provides toughness and chipping resistance, resolving the contradiction between wear resistance and chipping resistance through functional segmentation.
Solution Approach 2:
Each sublayer has locally optimized composition and properties tailored to its specific function. The first sublayer has higher Al content for adhesion, the second sublayer has optimal TiAlN composition for hardness, and the third sublayer has B addition for toughness, creating local quality variations that collectively solve the contradiction.
Data Source
AI summary
A surface-coated cutting tool comprises a tool substrate comprising a cBN sinter and a hard coating layer including a lower sublayer α and an upper sublayer β on the surface of the cutting edge; wherein α satisfies (Al1-xTix)N (0.40≤x≤0.60); β satisfies (Al1-y-zTiyBz)N (0.40≤y≤0.60 and 0.01≤z≤0.10); in the sublayer β, the variation in the concentration of the B component is repeated; the average Bmaxav of the maxima in the concentration of the B component satisfies z<Bmaxav≤2.0×z, and the average Bminav of the minima in the concentration of the B component satisfies 0≤Bminav<z; and the average thickness tα of α and the average thickness tβ of β satisfy expression: 2.0≤tβ/tα≤6.0; and the residual stress σ of the overall hard coating layer satisfies −2.0 GPa≤σ≤−0.5 GPa.