Alternating Nitride Coating Structure for Crack-Resistant Cutting Tools
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Solution Overview
Problem
The fracture resistance of existing coated cutting tools is inadequate, leading to cracking and reduced tool life during high-speed machining, particularly due to increased speed, feed, and depth of cut.
Innovation Solution
A coated cutting tool with an alternating laminate structure comprising specific composite nitride layers, including (Al 1-x Cr x )N and (Ti 1-y Si y )N, optimized in terms of atomic ratios, thickness, and elastic modulus to hardness ratio, enhancing both wear resistance and fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cutting speed, feed, and depth of cut are increased for high-speed machining, then productivity is improved, but the cutting edge undergoes cracking due to applied load, reducing tool life
Solution Approach 1:
The patent applies composite material principles by creating a multilayer coating structure consisting of alternating hard layers (TiAlSiN4) and tough layers (AlCrN). This composite structure combines the high hardness of TiAlSiN4 for wear resistance with the high toughness and crack resistance of AlCrN, allowing the tool to withstand the mechanical loads of high-speed machining while maintaining extended tool life
Solution Approach 2:
The coating is segmented into multiple thin sublayers (at least four alternating sublayers) rather than using a single thick coating. Each sublayer has a thickness of 0.5-15 nm, creating a fine-grained composite structure that prevents crack propagation while maintaining overall coating integrity under high loading conditions
Data Source
Figure 1
AI summary
A coated cutting tool comprising a substrate and a coating layer formed on the substrate, wherein: the coating layer has an alternating laminate structure of an alternating laminate of: a first composite nitride layer containing a compound having a composition represented by formula (1) below: (Al1-xCrx)N (1) (wherein x denotes an atomic ratio of the Cr element based on a total of the Al element and the Cr element and satisfies 0.10 ≤ x ≤ 0.50); and a second composite nitride layer containing a compound having a composition represented by formula (2) below: (Ti1-ySiy)N (2) (wherein y denotes an atomic ratio of the Si element based on a total of the Ti element and the Si element and satisfies 0.00 < y < 1.00); an average thickness of each of the layers of the first composite nitride layer is from 70 nm or more to 300 nm or less, and an average thickness of each of the layers of the second composite nitride layer is from 70 nm or more to 300 nm or less; and a ratio [H/E] of a hardness H of the alternating laminate structure to an elastic modulus E of the alternating laminate structure is from 0.06 or more to 0.08 or less.