Surface-Coated Cutting Tool Compressive Stress Wear Resistance
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Solution Overview
Problem
Surface-coated cutting tools face challenges in achieving both high wear resistance and fracture resistance, while also having an indicator function to determine usage, due to tensile residual stress and color loss during mechanical processing, which affects adhesion and durability.
Innovation Solution
A surface-coated cutting tool with a titanium boride layer having compressive residual stress of 0.1 GPa or more, combined with an aluminum oxide layer and an intermediate layer, applied through chemical vapor deposition and post-processing techniques like blasting or brushing, to enhance wear resistance and maintain color for usage indication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a coating is formed by chemical vapor deposition to achieve high wear resistance, then the coating has high adhesion strength and wear resistance, but tensile stress remains in the coating due to thermal expansion difference, which promotes crack propagation and reduces fracture resistance
Solution Approach 1:
The patent changes the stress state parameter from tensile to compressive by applying post-deposition surface treatment (shot peening, laser peening, or plasma treatment). This parameter change eliminates the harmful tensile stress that promotes crack propagation while maintaining the high wear resistance provided by the thick coating.
Solution Approach 2:
The patent applies surface treatment immediately after coating deposition to convert the stress state before the coating is put into service. This preliminary action prevents the development of crack propagation conditions that would occur during normal tool usage.
2Reliability
If the surfaces of coated tools are subjected to mechanical processing to eliminate tensile residual stress, then the fracture resistance improves, but the color of the outermost layer may be lost, making it difficult to determine the usage thereof
Solution Approach 1:
The patent replaces conventional mechanical surface processing (which removes material and alters color) with non-contact or minimal-contact methods such as laser peening, plasma treatment, or shot peening with fine particles. These methods generate compressive stress through energy input or particle impact without significantly altering the surface color or material removal.
Solution Approach 2:
The patent changes the method of stress application from mechanical removal to energy-based or particle-based induction. This parameter change in the processing method allows stress modification while preserving the optical properties of the coating.
3Reliability
If mechanical processing is applied to eliminate tensile residual stress, then the adhesion between coating and substrate improves, but the wear resistance may decrease due to wear of the outermost layer
Solution Approach 1:
The patent substitutes mechanical surface processing with alternative methods (laser peening, plasma treatment, or shot peening) that induce compressive stress without significant material removal. This substitution maintains both improved adhesion and preserved wear resistance.
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 both high wear resistance and fracture resistance, along with a clear indicator function for determining tool usage, improving tool maintenance and extending tool life by maintaining color and hardness during mechanical processing.
Implementation Method 1
These coatings are formed by chemical vapor deposition processes, such as chemical vapor deposition (CVD)
Implementation Method 2
a tensile stress remains in the coating due to the difference in thermal expansion coefficient between the cemented carbide substrate and the coating
Implementation Method 3
applying a compressive residual stress of 0.1 GPa or more in absolute value to a surface layer of the plurality of layers by a process selected from blasting, brushing, barreling, and ion implantation
Data Source
AI summary
Provided is a surface-coated cutting tool having both high wear resistance and high fracture resistance and having an indicator function that significantly facilitates the determination of the usage of a cutting edge. A surface-coated cutting tool according to an embodiment of the present invention includes a substrate and a coating formed on the substrate. The coating includes a plurality of layers. A surface layer of the plurality of layers is a titanium boride layer made of TixBy (where x and y are expressed as atomic percentages and satisfy 1.5 < y/x < 2.5) and has a compressive residual stress of 0.1 GPa or more in absolute value.