HIPIMS Coating Process for TiAlN Phase Control
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Solution Overview
Problem
Existing PVD coating processes face challenges in achieving coatings with improved properties such as high hardness, low stress, and age hardening effects, particularly in depositing layers with high aluminum content without precipitating the wurtzite AlN phase that degrades coating properties.
Innovation Solution
A process involving at least two unbalanced magnetron cathodes with different metal compositions, where one cathode is operated using high power impulse magnetron sputtering (HIPIMS) with predominantly aluminum and the other with titanium, silicon, or other metals, and employing pulsed electrical power to achieve high current densities and controlled bias voltages to prevent wurtzite phase formation and enhance coating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional DC sputtering is used to deposit high aluminum content coatings, then the coating can be formed, but the wurtzite AlN phase precipitates which degrades coating properties such as hardness and wear resistance
Solution Approach 1:
The patent applies periodic pulsed power instead of continuous DC power to the magnetron cathode. The pulse duration is specifically optimized to allow aluminum deposition while preventing wurtzite phase formation. This periodic action enables the deposition of high aluminum content coatings (up to 64 at.% Al) while maintaining the cubic TiAlN phase structure, thereby resolving the contradiction between achieving high aluminum content and preventing harmful phase precipitation.
2Strength
If high aluminum content is deposited to improve coating properties, then wear resistance can be enhanced, but residual stress increases and coating quality deteriorates
Solution Approach 1:
The pulsed power regime with optimized pulse duration creates periodic deposition cycles that control aluminum incorporation while managing stress accumulation. The pulsed nature of the process allows for stress relaxation between pulses, enabling the deposition of high aluminum content coatings with reduced residual stress compared to conventional DC sputtering.
Solution Approach 2:
The patent changes the electrical power supply parameters from continuous DC to pulsed mode, and also optimizes the substrate bias voltage. These parameter changes enable the deposition of high aluminum content coatings while controlling residual stress levels and maintaining coating quality.
3Productivity
If pulsed power with high current density is applied to increase aluminum deposition rate, then productivity improves, but control over phase formation becomes more difficult
Solution Approach 1:
The patent uses periodic pulsed power with specifically optimized pulse duration to achieve high aluminum deposition rates while maintaining precise control over phase formation. The pulsed regime creates controlled metal-ion-rich periods that favor cubic phase formation, preventing wurtzite phase precipitation even at high deposition rates.
Solution Approach 2:
The pulsed power regime provides inherent feedback control through the periodic nature of the process. The pulse duration and duty cycle can be optimized based on the desired coating properties, allowing for precise control of aluminum content and phase composition while maintaining high productivity.
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 process results in coatings with high hardness, low residual stress, and age hardening effects, achieving Al content up to 64% in the cubic TiAlN phase without wurtzite AlN formation, leading to improved mechanical properties and wear resistance.
Implementation Method 1
A plasma is generated by supplying electrical power to the cathodes, so that the targets are sputtered by ions. The sputtered material from the sputtering targets is deposited as a coating on a substrate arranged within the vacuum chamber.
Implementation Method 2
The invention relates to coating of substrate by means of a physical vapor deposition (PVD) process, in particular by magnetron sputtering.
Implementation Method 3
According to the HIPIMS process, electrical power is supplied in very short, yet extremely powerful pulses. During the resulting discharge, high current densities are reached at the targets.
Implementation Method 4
A plasma is generated by supplying electrical power to the cathodes, so that the targets are sputtered by ions.
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5d
AI summary
A process and a device for coating a substrate (22) are described. In a vacuum chamber (10), a first magnetron cathode (24) is provided with a sputtering target (28) of a first metal composition comprising predominantly aluminium.A second magnetron cathode (26) is provided with a sputtering target (30) of a second metal composition comprising at least 50 at-% of a second metal selected from groups IVA – VIA of the periodic table. In order to obtain coatings with improved properties, electrical power is supplied to the cathodes (24, 26) such that the targets (28, 30) are sputtered, where electrical power is supplied to the first cathode (24) as pulsed electrical power according to high power impulse magnetron sputtering with a first peak current density, and to the second cathode (26) with a second peak current density lower than the first peak current density. The substrate (22) is arranged within the vacuum chamber such that particles from the plasma deposit onto the substrate forming a coating.