Cutting Tool Wear-Resistant Coating with Aperiodic TiN-AlN Layers
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Solution Overview
Problem
Modern metal cutting tools face challenges in achieving high wear resistance, toughness, and resistance to plastic deformation, particularly when using magnetron sputtered multilayer coatings with insulating layers like AlN, which can lead to softening and surface defects.
Innovation Solution
A metal cutting tool with a substrate coated using a PVD Bipolar Pulsed Dual Magnetron Sputtering technique, featuring a multilayered structure of alternating nitride or carbide layers with at least one electrically isolating layer, deposited using a configuration of alternating TiN and AlN layers with varying thickness and composition to achieve high hardness and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If magnetron sputtering is used to deposit multilayer coatings with insulating layers like AlN, then wear resistance and hardness are improved, but softening and surface defects occur
Solution Approach 1:
The patent applies periodic pulsed deposition cycles where insulating layers (AlN) and conducting layers (TiN) are alternately deposited in repeated sequences. This periodic action allows the insulating layer to provide hardness and wear resistance while the conducting layer prevents softening and surface defects by maintaining electrical conductivity throughout the coating structure
Solution Approach 2:
The patent creates a composite multilayer coating structure combining electrically insulating AlN layers with electrically conducting TiN layers. This composite structure integrates the beneficial properties of both materials: the hardness and oxidation resistance of AlN with the electrical conductivity and softening prevention of TiN
2Strength
If Al content in TiAlN layer is increased beyond 56 at-%, then hardness and oxidation temperature improve, but above 75 at-% the layer becomes soft due to hexagonal AlN formation
Solution Approach 1:
The patent changes the compositional parameter by using pure AlN (100% Al content) in the insulating layers rather than TiAlN with high Al content. This parameter change avoids the hexagonal phase formation issue that occurs in TiAlN when Al exceeds 75 at-%, while still achieving the desired hardness and oxidation resistance through the cubic AlN structure in the multilayer configuration
3Ease of manufacture
If elemental Al targets are used for magnetron sputtering, then AlN layer deposition is enabled, but insulating AlN forms at the surface causing deposition problems
Solution Approach 1:
The patent uses periodic pulsed deposition where AlN layers are deposited in controlled pulses followed by TiN layer deposition. This periodic action prevents insulating AlN surface formation problems by intermittently introducing conducting TiN that maintains surface conductivity during the deposition process
Solution Approach 2:
The patent introduces TiN layers as intermediary conducting layers between AlN deposits. These TiN intermediaries prevent the buildup of insulating AlN on the surface by providing conductive pathways, thereby maintaining deposition stability and coating uniformity
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 a cutting tool with enhanced hardness, wear resistance, and temperature stability, suitable for high-speed machining, with adjustable Al content and layer structure optimizing properties for specific machining demands.
Implementation Method 1
depositing a refractory multilayer consisting of nitride or carbide layers or mixtures thereof... by PVD Bipolar Pulsed Dual Magnetron Sputtering technique
Implementation Method 2
PVD Bipolar Pulsed Dual Magnetron Sputtering technique for producing such a tool
Data Source
AI summary
The present invention relates to a cutting tool comprising a substrate and, a wear resistant coating, said wear resistant coating is composed of one or more layers of refractory compounds of which at least one layer consists of a multilayered MX/LX/MX/LX laminar structure where the alternating layers MX and LX are carbides or nitrides with the elements M and L selected from the group consisting of Ti, Nb, Hf, V, Ta, Mo, Zr, Cr, Al, Si or W and mixtures thereof, wherein the sequence of individual layer thicknesses has no repeat period but essentially aperiodic throughout the entire multilayered structure, and where the individual MX and LX layer thickness is larger than 0.1 ran but the sum of any 10 consecutive layers in the structure is smaller than 300 nm, and the total thickness of said multilayered structure is larger than 0.5 μm but smaller than 20 μm, deposited by PVD-technique, where at least one of MX or LX are electrically isolating, and a method of making such a cutting tool.