Multilayer Coated Cutting Tool for Small-Diameter Steel Cutting
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Solution Overview
Problem
Coated cutting tools with a nitride or carbonitride of TiSi on a nitride or carbonitride of AlCrSi having a high Si content ratio and fine film structure exhibit insufficient durability, particularly in small-diameter tools with diameters less than 1 mm or 0.5 mm, when applied to high-hardness steel cutting.
Innovation Solution
A coated cutting tool with a layer A composed of a nitride or carbonitride containing 50-70% Al, 20-45% Cr, and 4-15% Si, and a layer B with 70-90% Ti, 5-20% Si, and 1-10% Nb or Cr, both with a face-centered cubic lattice structure, enhances durability by improving wear resistance and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a nitride or carbonitride of TiSi is applied on a nitride or carbonitride of AlCrSi with high Si content ratio and fine film structure, then wear resistance is improved, but durability is insufficient in small-diameter tools
Solution Approach 1:
The coating is divided into multiple layers with different compositions and functions: a base layer (AlCrSi nitride/carbonitride) providing fine film structure and wear resistance, and an intermediate layer (TiSi nitride/carbonitride) enhancing durability. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between wear resistance and durability in small-diameter tools.
Solution Approach 2:
The invention uses composite coating structures combining different nitride/carbonitride materials (AlCrSi-based and TiSi-based) with specific composition ratios. The composite structure integrates the fine film structure characteristics of AlCrSi nitride/carbonitride with the durability-enhancing properties of TiSi nitride/carbonitride, achieving both wear resistance and durability simultaneously.
2Strength
If Si content ratio is increased to make film structure finer, then wear resistance is improved, but durability in small-diameter tools remains insufficient
Solution Approach 1:
Different regions of the coating have different Si content ratios and material compositions tailored to their specific functions. The base layer has optimized Si content for fine film structure and wear resistance, while the intermediate layer has different composition for durability. This local quality differentiation resolves the contradiction by allowing each region to optimize for its primary function.
Data Source
AI summary
A coated cutting tool which has, on a surface of a substrate, a layer A of a face-centered cubic lattice structure which is a nitride or carbonitride containing 50 atom % or more of Al, 20 atom % or more of Cr, 85 atom % or more of Al and Cr, and 4 atom % or more and 15 atom % or less of Si, and a layer B provided on the layer A. The layer B is a nitride or carbon nitride which contains 70 atom % or more and 90 atom % or less of Ti, 5 atom % or more and 20 atom % or less of Si, and 1 atom % or more and 10 atom % or less of Nb or Cr in terms of a total amount of metal (including metalloid) elements, and has the face-centered cubic lattice structure.