Laminated cBN Tool Coating for Intermittent Cutting Wear and Fracture
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Solution Overview
Problem
Conventional coated tools experience fractures and reduced wear resistance under strong intermittent cutting conditions, leading to a short tool service life due to intermittent and impact high loads.
Innovation Solution
A surface-coated cubic boron nitride sintered material tool with a hard coating layer having an alternate laminated structure of (Ti, Al)N and (Cr, Al, M)N layers, where the B layer's outermost surface exhibits high hardness and a plastic deformation work ratio of 0.35 to 0.50, enhancing adhesion strength and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is applied to improve wear resistance, then wear resistance is improved, but fracture resistance deteriorates under strong intermittent cutting conditions
Solution Approach 1:
The hard coating layer is divided into multiple sub-layers with different compositions and functions. The gradient structure includes a first sub-layer with higher toughness and a second sub-layer with higher hardness, allowing each sub-layer to perform its specialized function while working together as a unified coating system.
Solution Approach 2:
The coating structure transitions from a uniform single-layer design to a gradient multi-layer design with continuously varying composition and properties. The aluminum content decreases from the first sub-layer to the second sub-layer, creating a gradual parameter change that optimizes both fracture resistance and wear resistance.
2Device complexity
If a single-layer hard coating is used to maintain simplicity, then device complexity is reduced, but both wear resistance and fracture resistance cannot be simultaneously optimized
Solution Approach 1:
The coating is segmented into functional zones with distinct properties. The first sub-layer provides fracture resistance and adhesion, while the second sub-layer provides wear resistance, allowing simultaneous optimization of multiple performance aspects without excessive complexity.
Solution Approach 2:
The coating uses composite material architecture with different nitride compositions ((Ti,Al)N and (Cr,Al)N) arranged in a gradient structure. This composite approach combines the advantages of different materials to achieve properties that cannot be obtained with a single material system.
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 tool exhibits excellent fracture resistance and wear resistance for extended periods, even under strong intermittent cutting conditions, effectively managing impact loads and maintaining cutting performance.
Implementation Method 1
a complex nitride layer of Cr and Al ((Cr, Al)N) or a complex nitride layer of Ti and Al ((Ti, Al)N) as a hard coating layer through an arc ion plating method
Data Source
Figure 1
Figure 2A~2B
Figure 3(a)~3(b)
AI summary
The present invention is directed to a surface-coated cubic boron nitride sintered material tool including a cBN substrate and a hard coating layer formed on a surface of the cBN substrate and having an alternate laminated structure of A layer and B layer. The cBN substrate (sintered material) includes: a Ti compound, WC, AlN, TiB2, Al2O3, and cBN. The A layer has a composition of (Ti1-xAlx)N (0.4≤x≤0.7 in terms of atomic ratio). The B layer has a composition of (Cr1-y-zAlyMz)N (0.03≤y≤0.4 and 0≤z≤0.05 in terms of atomic ratio). A plastic deformation work ratio of the B layer is 0.35 to 0.50.