Composite Nitride Coating for Fracture-Resistant Cutting Tools
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Solution Overview
Problem
Conventional cutting tools fracture due to increased cutting speeds, feeding speeds, and temperature fluctuations, leading to cracks in the tool surface and substrate, which existing coated cutting tools with high wear resistance cannot effectively address.
Innovation Solution
A coated cutting tool with a composite nitride layer of specific composition and structure, including a cubic crystal system with controlled lattice constants and residual stress, applied in multiple layers to enhance both wear and fracture resistance without reducing tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional coated cutting tool with high wear resistance is used, then wear resistance is improved, but fracture resistance deteriorates under increased cutting speeds and temperature fluctuations
Solution Approach 1:
The coating layer is divided into multiple distinct layers with different functions: a wear-resistant outer layer and a fracture-resistant intermediate layer. This segmentation allows each layer to optimize its specific function without compromising the other, resolving the contradiction between wear resistance and fracture resistance.
Solution Approach 2:
The patent employs composite material structure with multiple coating layers having different compositions and properties. The combination of materials with contrasting characteristics (high wear resistance vs. high fracture resistance) creates a synergistic effect where the composite structure performs better than individual materials alone.
2Productivity
If cutting speed and feeding speed are increased to improve productivity, then productivity is improved, but tool fracture increases due to surface cracks and temperature fluctuations
Solution Approach 1:
The intermediate layer acts as a cushioning layer that absorbs and mitigates the impact of thermal stresses and mechanical loads before they reach the substrate. This beforehand cushioning prevents crack initiation and propagation, allowing higher cutting speeds without increasing fracture risk.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the coating layers, including composition, thickness, and microstructure, to optimize performance at high cutting speeds. By changing these parameters, the coating system can withstand the increased thermal and mechanical loads associated with higher productivity.
Data Source
AI summary
Provided is a coated cutting tool, comprising: a substrate; and a coating layer formed on at least part of a surface of the substrate. The coating layer includes at least one composite nitride layer including a compound having a composition represented by (TixAly)N [x denotes an atomic ratio of a Ti element based on a total of the Ti element and an Al element, y denotes an atomic ratio of the Al element based on a total of the Ti element and the Al element, and 0.10 ≤ x ≤ 0.50, 0.50 ≤ y ≤ 0.90, and x + y = 1 are satisfied]. The composite nitride layer includes a phase having a lattice constant of from 0.400 nm or more to 0.430 nm or less, and a phase having a lattice constant of from 0.755 nm or more to 0.810 nm or less.