PVD Coating Thickness and Stress Control via Bias Voltage
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Solution Overview
Problem
Existing hard-material coatings on metallic, ceramic, or hard-metal components face limitations in layer thickness, internal stresses, and post-processing capabilities, leading to premature wear and inability for surface treatments like regrinding or polishing.
Innovation Solution
A PVD process in a vacuum chamber with a nitrogen partial pressure above 2.5 Pa, using vacuum arc evaporators and varying electrical BIAS voltage and component movement speed to achieve hard-material coatings with increased thickness, reduced internal stresses, and inhomogeneous element distribution, allowing for post-processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional PVD or CVD processes are used to produce hard material coatings, then the coating hardness is improved, but the layer thickness is limited to at most 20 μm and internal stresses increase
Solution Approach 1:
The patent applies parameter changes by operating the PVD process at elevated nitrogen partial pressures (>2.5 Pa) and using high negative BIAS voltages (at least 250 V). These parameter changes enable the formation of dense, hard coatings with thicknesses exceeding 20 μm while controlling internal stresses, resolving the contradiction between coating hardness and achievable layer thickness.
2Strength
If conventional PVD or CVD processes are used to produce hard material coatings, then the coating hardness is improved, but internal stresses lead to premature wear or destruction
Solution Approach 1:
The patent uses parameter changes by applying high negative BIAS voltages (at least 250 V) during coating formation and maintaining elevated nitrogen partial pressures (>2.5 Pa). These parameters control the deposition process to reduce internal stresses while maintaining coating hardness, thereby improving coating durability and preventing premature failure.
Solution Approach 2:
The patent implements periodic action through intermediate treatments during the coating process, where the BIAS voltage or nitrogen pressure is temporarily adjusted to influence already formed coating layers. This periodic modification of process parameters allows stress management and quality improvement without compromising the overall coating hardness and durability.
3Strength
If thin hard material layers (≤20 μm) are produced using conventional methods, then coating hardness is achieved, but post-processing treatments like regrinding or polishing damage the coating
Solution Approach 1:
The patent applies parameter changes by producing coatings with thicknesses greater than 20 μm through modified PVD conditions (elevated nitrogen pressure >2.5 Pa and high BIAS voltage ≥250 V). This increased thickness provides a sufficient material reserve that allows post-processing treatments like regrinding or polishing to be performed without damaging the functional coating layer.
4Length of stationary object
If higher layer thicknesses are achieved using conventional PVD processes, then more material is deposited, but disruptive defects and internal stresses increase significantly
Solution Approach 1:
The patent resolves this contradiction by changing process parameters to elevated nitrogen partial pressures (>2.5 Pa) and high negative BIAS voltages (at least 250 V). These parameter changes enable the deposition of thick coatings (>20 μm) while maintaining coating quality by reducing internal stresses and preventing disruptive defects that would normally occur at such thicknesses with conventional processes.
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 method produces coatings with hardness above 2500 HV, low internal stresses, and fine crystalline structure, enabling layer thicknesses up to 150 μm and allowing for surface treatments like sharpening or polishing after production.
Implementation Method 1
Production takes place using a PVD process in a vacuum chamber
Implementation Method 2
it has proven advantageous to use one or more vacuum arc evaporators as the evaporator source
Implementation Method 3
At least during the formation of the coating, an electrically negative BIAS voltage of at least 250 V is applied to the component to be coated
Implementation Method 4
Production takes place using a PVD process in a vacuum chamber in which a nitrogen partial pressure of >2.5 Pa is maintained
Data Source
AI summary
Producing a hard material coating on metallic, ceramic or hard-metallic components, in which e.g. aluminum chromium nitride, aluminum chromium silicon nitride, aluminum titanium nitride or aluminum chromium silicon nitride/zirconium nitride is formed and have a layer thickness of at least 50 mu m, using a physical vapor deposition (PVD) method, in which within a vacuum chamber, in which a nitrogen partial pressure of greater than 2.5 (preferably greater than 5) Pa is maintained, contains at least one of metallic elements in the coating, and a silicon is contained in the coating, is claimed. Producing a hard material coating on metallic, ceramic or hard-metallic components, in which aluminum chromium nitride, aluminum chromium silicon nitride, aluminum titanium nitride, aluminum titanium silicon nitride, aluminum chromium nitride/titanium nitride, aluminum titanium silicon nitride/titanium nitride, aluminum chromium nitride/zirconium nitride or aluminum chromium silicon nitride/zirconium nitride is formed and have a layer thickness of at least 50 mu m, using a PVD method, in which within a vacuum chamber, in which a nitrogen partial pressure of greater than 2.5 (preferably greater than 5) Pa is maintained, contains at least one of the metallic elements in the coating, and a silicon is contained in the coating, is claimed, where a silicon-containing vapor source is operated to form the coating on the component surface, and an electrically negative bias voltage of at least 250 (preferably 500) V is applied at least during the formation of the coating to the component to be coated. An independent claim is included for the hard material coating manufactured by the above method, where the coating has a hardness of at least 2500 HV, thus the residual stress of the coating is less than 2 GPa and a fine crystalline structure with a grain size of smaller than 100 nm is observed and within the coating, the proportion of individual chemical elements forming the coating are varied.