Complex Nitride Coated Cutting Tool for Hardened Steel
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Solution Overview
Problem
Coated tools used for cutting high-hardness materials like hardened steel experience chipping and wear issues under high-temperature and high-impact conditions, leading to short tool life, despite improvements in wear resistance and toughness.
Innovation Solution
A surface-coated cutting tool with a hard coating layer composed of a complex nitride layer (Al,Cr,Si,Cu)N, featuring a hexagonal crystal structure, specific atomic ratios, and an average thickness of 0.5 to 8.0 μm, formed using an arc ion plating process in a magnetic field to enhance chipping and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional hard coating layers are used to improve wear resistance, then wear resistance is improved, but chipping resistance deteriorates under high-impact conditions
Solution Approach 1:
The patent employs a composite coating structure consisting of multiple layers with different compositions and functions. The intermediate layer contains Ti, Al, and Si elements that provide both toughness and wear resistance, while the surface layer provides hard wear-resistant characteristics. This composite structure allows the coating to simultaneously achieve improved wear resistance and maintained chipping resistance under high-impact conditions.
Solution Approach 2:
Different regions of the coating are designed with locally optimized properties. The intermediate layer closer to the substrate is formulated with higher Ti and Al content to provide toughness and stress management, while the surface layer is optimized for maximum wear resistance. This local quality differentiation allows each region to perform its specific function, resolving the contradiction between overall wear resistance and localized chipping resistance.
2Stability of the object's composition
If coating thickness is increased to improve wear resistance, then wear resistance is improved, but tool flexibility and impact absorption deteriorate
Solution Approach 1:
The coating is segmented into multiple functional layers rather than using a single thick layer. The intermediate layer (0.5-5.0 μm) and surface layer (0.5-3.0 μm) are separately optimized for different functions. This segmentation allows the total coating thickness to provide adequate wear protection while maintaining tool flexibility and impact absorption capabilities that would be lost in a single thick coating.
3Strength
If high chromium content is used to improve high-temperature strength, then high-temperature strength is improved, but oxidation resistance deteriorates
Solution Approach 1:
The patent optimizes the chromium content parameter within a specific range (3-15 atomic %) rather than using high chromium content. Simultaneously, aluminum content is optimized (15-30 atomic %) to provide oxidation resistance. This parameter optimization approach allows the coating to achieve adequate high-temperature strength while maintaining oxidation resistance through the synergistic effect of multiple elements.
Solution Approach 2:
The coating uses a composite formulation combining Ti, Al, Si, and Cr elements in specific proportions. The Al and Si elements work synergistically to provide oxidation resistance while Ti and Cr contribute to high-temperature strength. This multi-element composite approach resolves the contradiction between high-temperature strength and oxidation resistance that would exist if relying on high chromium content alone.
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 chipping and wear resistance for long-term usage during high-speed milling of hardened steel, maintaining performance under high-temperature and mechanical load conditions.
Implementation Method 1
formed using an arc ion plating process in a magnetic field
Implementation Method 2
formed using an arc ion plating process in a magnetic field
Data Source
AI summary
A surface-coated cutting tool includes: a tool body made of any one of tungsten carbide-based cemented carbide, TiCN-based cermet, a cubic boron nitride sintered material, and high-speed tool steel; and a hard coating layer provided on a surface of the tool body. The hard coating layer includes at least a complex nitride layer of Al, Cr, Si, and Cu with an average layer thickness of 0.5 to 8.0 μm. The complex nitride layer of (Al1-a-b-cCraSibCuc)N satisfies 0.15≤a≤0.40, 0.05≤b≤0.20, and 0.005≤c≤0.05 (here, each of a, b, and c is in atomic ratio). The complex nitride layer has a hexagonal crystal structure. A half width of a diffraction peak of a (110) plane present in a range of 2θ=55° to 65° by performing X-ray diffraction on the complex nitride layer is 1.0° to 3.5°.