Coated Cutting Tool Insert Toughness via Wet-Blasting
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Solution Overview
Problem
Current cutting tool inserts face challenges with high tensile stresses and coating delamination due to thick coatings, leading to reduced toughness and reliability, especially in low carbon steels and stainless steels, and require post-treatment techniques that can compromise surface finish and stress state.
Innovation Solution
A cutting tool insert with a cemented carbide substrate and a specific coating structure, including a cobalt binder phase with a high W-content, and a post-treatment using wet-blasting under controlled conditions to achieve a favorable tensile stress level and excellent surface finish, expanding the coating thickness range without performance penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the coating thickness is increased to improve wear resistance, then the wear resistance is improved, but the risk of coating delamination and reduced toughness increases
Solution Approach 1:
The coating is divided into multiple distinct layers (bonding layer, intermediate layer, wear resistance layer) with different functions and properties. This segmentation allows each layer to be optimized independently - the bonding layer adheres to the substrate, the intermediate layer provides transition and stress management, and the wear resistance layer provides protection, thereby achieving high wear resistance without excessive overall thickness that would cause delamination.
Solution Approach 2:
Different regions of the coating have different properties tailored to their specific functions. The bonding layer has high adhesion to the substrate, the intermediate layer has intermediate properties for stress management, and the wear resistance layer has high hardness and wear resistance. This local optimization allows the coating system to achieve high wear resistance while maintaining reliability through appropriate property distribution.
2Strength
If the coating thickness is increased to improve wear resistance, then the wear resistance is improved, but the toughness decreases making the cutting tool less reliable
Solution Approach 1:
The coating system is segmented into layers with different thicknesses and properties. The bonding and intermediate layers are relatively thin and flexible, maintaining toughness, while the wear resistance layer is optimized for protection. This segmentation allows the overall system to achieve high wear resistance without sacrificing the toughness needed for reliable cutting tool performance.
Solution Approach 2:
The coating is a composite structure combining different materials (TiC, TiN, Al2O3, CrN) in specific layers. This composite approach allows combining the toughness-providing layers with the wear-resistant layers, achieving both high wear resistance and adequate toughness for reliable cutting tool operation.
3Manufacturing precision
If post-treatment techniques are applied to smooth the coating surface, then the surface finish is improved, but the stress state of the coating is altered and coating surface finish may be compromised
Solution Approach 1:
The coating structure is designed in advance with appropriate layer thicknesses and material compositions that inherently provide good surface finish properties. The wear resistance layer is formulated and deposited to achieve the desired surface quality before any post-treatment, minimizing the need for subsequent stress-altering operations.
Solution Approach 2:
The surface finish is primarily controlled by changing the deposition parameters during CVD/PVD processes (temperature, pressure, gas flow rates, deposition speed) rather than relying on post-treatment. By optimizing these parameters, the coating achieves the required surface finish without requiring aggressive post-treatment that would alter the stress state.
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 solution provides improved toughness and adhesion, allowing for broader application ranges with enhanced cutting performance and surface smoothness, while maintaining edge security and resistance to high temperatures.
Implementation Method 1
The CVD technique is conducted at a rather high temperature range, 950-1050° C.
Implementation Method 2
The most frequent employed coating techniques are Chemical Vapour Deposition (CVD) and Physical Vapour Deposition (PVD).
Implementation Method 3
Every post treatment technique that exposes a surface, e.g., a coating surface to a mechanical impact as, e.g., wet or dry blasting
Data Source
AI summary
A CVD-coated cutting tool insert with improved toughness properties having the ability to withstand high temperatures without sacrificing edge line security is disclosed. The insert coating comprises a TiCxNy-layer with a low tensile stress level of 50-500 MPa and an α-Al2O3-layer with a high surface smoothness with a mean Ra<0.12 μm as measured by AFM-technique, obtained by subjecting the coating to an intensive wet blasting operation.