Coated Cutting Tool Insert TiOx Layer Residue Removal
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Solution Overview
Problem
Existing methods for post-treating coated cutting tools to remove TiC x N y O z residues from Al 2 O 3 surfaces are unreliable, leading to reduced flaking resistance, coating withdrawal, and discoloration, especially for thin Al 2 O 3 coatings, where lower blasting pressures are used to avoid damage.
Innovation Solution
A method involving a hard layer system on a cemented carbide substrate with a TiO x layer as the penultimate outermost layer, which is partially removed during blasting or brushing, ensuring the TiC x N y O z layer is lifted above the Al 2 O 3 surface for complete removal and minimizing surface coverage to prevent residue visibility and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blasting pressure is increased to remove TiC x N y O z residues, then cleaning effectiveness is improved, but Al 2 O 3 coating damage increases
Solution Approach 1:
A TiO x intermediate layer is deposited beforehand between the TiC x N y O z top layer and the Al 2 O 3 base layer. This preliminary layer serves as a sacrificial element that facilitates selective removal of the top layer during blasting while protecting the Al 2 O 3 layer from damage, enabling effective cleaning at lower blasting pressures.
Solution Approach 2:
The TiO x layer acts as an intermediary between the TiC x N y O z top layer and the Al 2 O 3 base layer. During blasting, this intermediate layer preferentially erodes, allowing the top layer to be removed while the Al 2 O 3 layer remains protected, thus mediating between the conflicting requirements of cleaning effectiveness and coating protection.
2Strength
If blasting pressure is decreased to protect Al 2 O 3 coating, then coating damage is reduced, but TiC x N y O z residue removal becomes incomplete
Solution Approach 1:
The TiO x intermediate layer is deposited in advance to create a controlled erosion pathway. This preliminary structure enables complete residue removal at lower blasting pressures by directing the blasting energy through the softer TiO x layer rather than directly impacting the Al 2 O 3 layer.
Solution Approach 2:
The introduction of TiO x changes the material parameter profile of the coating system. The TiO x layer has different erosion characteristics compared to Al 2 O 3, allowing blasting parameters to be optimized for complete top layer removal while maintaining lower pressures that protect the Al 2 O 3 layer from damage.
3Strength
If TiC x N y O z layer is made thicker for better wear resistance, then wear protection is improved, but residue removal difficulty increases
Solution Approach 1:
The coating system is segmented into distinct layers with different functions: the TiC x N y O z top layer provides wear resistance, while the intermediate TiO x layer facilitates post-treatment. This segmentation allows the top layer to be optimized for wear resistance without compromising residue removal, as the TiO x layer handles the removal process.
Solution Approach 2:
The TiO x intermediate layer mediates between the thick TiC x N y O z top layer and the blasting process. Even when the top layer is thick, the TiO x layer provides a controlled erosion pathway that enables complete residue removal without requiring excessive blasting pressure that would damage the Al 2 O 3 layer.
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
This approach effectively removes TiC x N y O z residues, maintaining Al 2 O 3 layer integrity, preventing discoloration, and enhancing tool performance by ensuring the absence of TiN residues on the Al 2 O 3 surface, thus extending the tool's lifetime.
Implementation Method 1
a post-treatment, preferably blasting or brushing, removing at least said outermost layer on the edge-line and on the rake face
Implementation Method 2
depositing onto a cemented carbide, titanium based or ceramic substrate, using known CVD methods a hard layer system
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3
AI summary
A method for making a coated cutting tool insert by depositing by CVD, onto a cemented carbide, titanium based or ceramic substrate a hard layer system, having a total thickness of about 2-50 µm, comprising at least one layer selected from titanium carbide, titanium nitride, titanium carbonitride, titanium carboxide and aluminum oxide, and an outer, 1-15 µm thick, aluminum oxide layer or (Al2O3 + ZrO2)*N multilayer, a penultimate outermost layer of TiOx, where x ranges from 1 to 2, and an outermost, 0.3-2 µm thick, TiCxNyOz layer, where x+y+z=1, x≥0, y≥0, and z≥0, followed by a post-treatment removing at least said outermost layer on the edge-line and on the rake face.