Are you currently looking to get a PVD coating? Unsure if PVD is the right choice for you? Worry not, as this article will give you a clear insight into PVD coating.
With so many types of metal coating in Dubai, it can be challenging to settle on any one method. This is because all of them pose a cost constraint and a durability constraint. The best metal fabricating companies highly recommend PVD coating in Dubai. This article will give you a clear insight as to why that is.
What is PVD Coating?
Table of Contents
Physical Vapor Deposition (PVD) coating refers to a variety of thin-film deposition where a solid material is vaporized in a vacuum environment. The material is then deposited on substrates as a pure material or an alloy coating.
It is used to change the surface properties of the object to be coated. Where new mechanical, chemical, electrical, or optical characteristics are needed.
PVD coating was initially used in ballistics, prolonging the life of cannons and reducing spin by reducing friction and wear. It has, however, found many other uses.
In early discoveries, the scientists noticed that, at times, the colors would change. The discovery prompted their imagination, and they realized they could create varying shades in a repeatable fashion.
From this realization, a myriad of new possibilities opened up. A combination of aesthetics and functionality gives PVD coating a unique place in metalworking.
Creating PVD is a process that involves treating the surface of a metal to change its molecular properties.
The process of creating PVD coating
Creating a PVD coating is carried out in a vacuum chamber at a temperature between 50 and 600 degrees Celsius.
It is known as a “line of sight” technique, which means that the atoms vaporized from the solid material travel through the vacuum chamber and embed themselves into whatever object is in its path.
Different types of PVD coatings will result in different material properties. Even though a coating may look the same, how you make the coating has a substantial impact on the properties of the coating and how it will perform in the application required.
There are three processes for creating a PVD coating, these are;
- Ion beam sputtering
- Magnetron sputtering
- evaporation
Ion beam sputtering
Ion beam sputtering is when an ion beam is directed on a target—resulting in an ion bombardment. The process removes material from the target, which is deposited on the substrate surface. Adding reactive gases such as oxygen allows reactive ion beam sputtering of, e.g., dielectric materials.
By adding an assist ion beam source, an extra ion bombardment at the substrate can be introduced. This is used to influence the growing film or pre-clean the substrate.
Advantages of ion beam sputtering.
- Ion beam energies are precisely adjustable with the small energetic distribution.
- High surface mobility of condensing particles leads to smooth and defect-free films.
- Low sputtering pressure and low process temperatures enable dense layer growth and outstanding layer properties.
- Additional densification and modification (e.g., oxidation) by assisting ion beam source.
Magnetron sputtering
Magnetron sputtering uses a cathode with a permanent magnetic field to excite a dense plasma at the cathode surface.
The target material, placed at the cathode surface, is physically sputtered by ion bombardment and assists in being deposited on the substrate surface.
Thereby several process arrangements lead to different layer properties.
Sputtering with Single Magnetron
The process chamber contains one magnetron with a rotating magnetic field and a target diameter more prominent than the substrate diameter. The arrangement allows thin films with high throughput.
Confocal Sputtering
The sputter arrangement consists of up to 4 Magnetrons. The magnetrons are each smaller target diameter than substrate diameter. The magnetrons can be combined for different target materials or the same target materials.
To achieve a homogeneous material mix on the substrate surface, a sufficiently fast substrate rotation is required.
Dynamic Sputter Deposition
The rotating substrate is moved over rectangular magnetrons to produce multilayer coatings.
Individual emission profiles of the magnetrons are compensated by pre-calculation of the movement profiles. Enabling the layer thickness to be controlled by speed variation.
Advantages of magnetron sputtering.
- High deposition rate.
- Good process repeatability for multilayers with uniform thickness.
- Optional pretreatment with additional ion beam source (for dynamic sputter deposition).
- The low energy of the sputtered particles leads to smooth surfaces.
Evaporation
Also known as electron beam evaporation. The process involves passing Current through a tungsten filament, causing an electron emission. This is unified and accelerated to an electron beam by high voltage.
A magnetic field deflects the e-beam so that it is focused on the crucible. The material in the crucible is bombarded with that e-beam and evaporates to a gaseous state for deposition on the substrate to be coated.
Advantages of evaporation
- High deposition rates for evaporation of high-temperature materials and refractory metals.
- Stress optimized process design with medium layer density (with assist ion beam source).
- Deposition of films with nearly the same purity as the target material.
- Water-cooled crucible for controlled evaporation of target material and to avoid unwanted contamination.
The PVD standard coating materials
The coating material that will be sputtered or vaporized is known as a “target” or “source material.” There are hundreds of materials commonly used in PVD.
Depending on the end product, materials range from metals, alloys, ceramics, compositions, and anything from the periodic table.
Common PVD coating materials are titanium, zirconium, aluminum, stainless steel, and copper, though gold for aerospace electronics is often requested.
These coatings can be applied to a wide variety of substrates. This includes nylon, plastics, glass, ceramics, and metals, including stainless steel and aluminum.
To achieve a uniform thin film coating thicknesses that are often a few atoms or molecules thick. Parts to be coated are often rotated on several axes at a uniform speed. They are then placed on a conveyor belt moving past the deposition material’s plasma stream. Single or multi-layered coatings can be applied during the same deposition cycle.
PVD Applications
There is a wide range of applications for PVD, so it is commonly used in high-tech industries.
Some of the industries and applications in which we have applied PVD coatings include;
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Architectural
PVD-colored stainless steel is well used in the architectural and industrial design industry. Examples include;- stainless steel curtain walls, cladding and profiles for hotels and casinos, shopping centers, railway stations and facades, and fit-outs of high-end retail stores.
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Transport
PVD coated stainless steel can also be used in the transport industry, such as;- ceiling and wall cladding to shipping or seating, skirting, and paneling on trains.
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Ironmongery
At the smaller end of the scale, the colored steel can be used for display cases, furniture, lighting fixtures, door handles, and taps.
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Jewelry
The PVD process can also be used on stainless steel jewelry – achieving some striking colors. The PVD stable colors are gold, rose gold, coffee, black, dark grey, and blue. According to the product surface polish finish, all these colors are polished, satin, or matt finish.
For gold and rose gold finish, real gold (maybe 14Kor 18K) is evaporated and deposited on the part under high temperatures or via ion bombardment. The shade of the gold achieved is according to the gold content of the target. Colour pigments or gas together with the TiN layer are used to achieve other shades.
Benefits and drawbacks of PVD coating
PVD coating benefits are many. PVD can provide a lifetime of protection from daily cleaning, which adds durability and value to your product. Traditional electroplating of brass, nickel, and gold finishes requires a clear coat that degrades with time and can quickly tarnish or corrode.
However, PVD requires no clear topcoats that fade or dull. It is four times harder than chrome which makes it corrosion and scratch-resistant.
Here are the advantages and disadvantages of PVD coating.
Advantages:
- PVD coatings are sometimes more complex and more corrosion resistant than coatings applied by the electroplating process. Most coatings have high temperature, good impact strength, excellent abrasion resistance, and are so durable that protective topcoats are rarely necessary.
- Ability to utilize virtually any type of inorganic and some organic coating materials on an equally diverse group of substrates and surfaces using a wide variety of finishes.
- More environmentally friendly than traditional coating processes such as electroplating and painting.
- More than one technique can be used to deposit a given film.
Disadvantages：
- Specific technologies can impose constraints; for example, the line-of-sight transfer is typical of most PVD coating techniques. However, some methods allow full coverage of complex geometries.
- Some PVD technologies typically operate at very high temperatures and vacuums, requiring special attention by operating personnel.
- Requires a cooling water system to dissipate large heat loads.
Conclusion
The bottom line is that ensuring you are familiar with PVD coating will enable you to choose the best metal fabricator for your project.
At eminence metal, we offer the best PVD coating solutions for you. Reach out to us today to discuss your project to ensure both quality and value for your money.
