Alternating TiAlN Coating Structure to Prevent Tool Delamination
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Solution Overview
Problem
Surface-coated cutting tools face challenges with adhesion fracture and delamination when cutting difficult-to-cut materials like nickel-based heat-resistant alloys, leading to reduced tool lifetime due to temperature increases and compressive stress in coating films.
Innovation Solution
A surface-coated cutting tool with an alternate layer structure composed of TiAlN layers, where the first and second layers are close in composition to prevent crack propagation and delamination, and an adhesive layer is introduced between the substrate and the alternate layer to enhance peeling strength, using a substrate with WC particles for improved hardness and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on a substrate to improve wear resistance and oxidation resistance at high temperatures, then the tool can cut difficult-to-cut materials like nickel-based heat-resistant alloys, but adhesion fracture and delamination occur due to compressive stress in the coating film
Solution Approach 1:
The coating film is divided into multiple thin layers (first layer and second layer) with different compositions (TiAlN with different Al content). This segmentation prevents crack propagation through the entire coating thickness and reduces delamination by creating a gradient structure that accommodates thermal and mechanical stresses.
Solution Approach 2:
The coating film uses a composite structure combining TiAlN layers with varying aluminum content. The first layer has composition TiaAlbSicN and the second layer has TidAleSifN, creating a composite material system that balances hardness, toughness, and adhesion properties to resist both wear and compressive stress.
2Reliability
If the coating film is made harder to improve wear resistance, then oxidation resistance at high temperatures is maintained, but compressive stress increases leading to adhesion fracture
Solution Approach 1:
Different regions of the coating film have different compositions optimized for different functions. The first layer with composition TiaAlbSicN provides hardness and wear resistance, while the second layer with composition TidAleSifN provides stress relief and adhesion. This local quality differentiation allows the coating to resist wear without accumulating excessive compressive stress throughout the entire film.
Data Source
AI summary
A surface-coated cutting tool includes a substrate and a coating film. The coating film includes an alternate layer. The alternate layer includes a first layer having a first composition and a second layer having a second composition. The alternate layer is formed by alternately stacking at least one first layer and at least one second layer. The first layer and the second layer each have a thickness not smaller than 2 nm and not greater than 100 nm. The first composition is expressed as TiaAlbSicN (0.25≤a≤0.45, 0.55≤b≤0.75, 0≤c≤0.1, a+b+c=1). The second composition is expressed as TidAleSifN (0.35≤d≤0.55, 0.45≤e≤0.65, 0≤f≤0.1, d+e+f=1). The first composition and the second composition satisfy a condition of 0.05≤d−a≤0.2 and 0.05≤b−e≤0.2.