Surface-Coated Cutting Tool With Nanoscale W-Modulated Upper Layer
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Solution Overview
Problem
Existing coated tools face challenges with chipping and fracture resistance during high-load cutting operations, such as deep hole drilling, despite exhibiting good wear resistance under normal conditions.
Innovation Solution
A surface coated cutting tool with a coating layer comprising a lower layer of (Al, Cr)N, an intermediate layer of (Al, Cr, Si)N with a repeated variation in Si level, and an upper layer of (Ti, Si, W)N with a repeated variation in W level, all deposited on a tool substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer of composite nitride (Al, Cr)N is formed on the tool substrate, then wear resistance is improved, but chipping resistance and fracture resistance deteriorate under high-load cutting conditions
Solution Approach 1:
The coating layer is divided into multiple functional layers: a lower layer of (Al, Cr)N for wear resistance, an intermediate layer of (Al, Cr, Si)N with repeated Si variation for toughness and stress relief, and an upper layer of (Ti, Si, W)N for oxidation resistance. This segmentation allows each layer to specialize in different protective functions, resolving the contradiction between wear resistance and chipping resistance
Solution Approach 2:
The intermediate layer features local quality variation through repeated Si level changes (maxima and minima) at the nanoscale. This creates alternating regions of different properties within the same layer, providing both toughness enhancement and stress distribution capabilities locally, which prevents chipping while maintaining overall wear resistance
2Duration of action of stationary object
If the coating layer thickness is increased to improve wear resistance, then tool life under normal conditions is extended, but chipping and fracture susceptibility increases under high-load operations
Solution Approach 1:
Instead of using a single thick coating layer, the invention segments the coating into multiple thinner functional layers with total thickness optimized for both wear and impact resistance. The intermediate layer with Si variation acts as a stress-absorbing buffer that prevents crack propagation, allowing the tool to withstand high-load conditions while maintaining extended tool life
Solution Approach 2:
The intermediate layer of (Al, Cr, Si)N with repeated Si variation serves as a pre-designed cushioning layer that absorbs and distributes stress before it can propagate into chipping or fracture. This beforehand cushioning structure is built into the coating system to prevent damage under high-load conditions
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 coated tool achieves excellent chipping resistance, fracture resistance, and wear resistance even under high-load cutting conditions, extending tool life and preventing breakage.
Implementation Method 1
a hard coating layer composed of a composite nitride layer of aluminum and chromium formed on a surface of a tool substrate composed of tungsten carbide (hereinafter referred to as WC) based cemented carbide by arc ion plating
Data Source
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AI summary
A surface coated cutting tool comprises: a tool substrate and a coating layer on a surface of the tool substrate; wherein the coating layer comprises a lower layer, an intermediate layer, and an upper layer, in sequence from the tool substrate toward the surface of the tool. The lower layer comprises an A layer having an average composition represented by formula: (Al1-xCrx)N, where x is 0.20 to 0.60; the intermediate layer comprises a B layer having an average composition represented by formula: (Al1-a-bCraSib)N, where a is 0.20 to 0.60 and b is 0.01 to 0.20; and the upper layer comprises a C layer having an average composition represented by formula: (Ti1-a-βSiαWβ)N where α is 0.01 to 0.20 and β is 0.01 to 0.10; and the upper layer has a repeated variation in W level with an average interval of 1 nm to 100 nm between adjacent local maxima and minima.