FAQ

#1 How does PVD coating work?

In the PVD coating process, the parts are placed in a chamber in which a clean vacuum of approximately 1 mPa is created. Subsequently, a plasma is generated which etches the target materials (targets). The released material hits the substrate and forms either a ceramic or metallic layer. Once the coating is complete, the substrate is removed and the process is complete. For a closer look at the coating technology, see our website PVD Coating Technology.

#2 Why use PVD coatings?

PVD Coatings are characterized by high hardness, excellent corrosion and wear resistance, and excellent frictional properties. These properties ensure long life and reliability of the coated parts.

#3 What materials can be coated?

PVD coating can be applied to a wide range of materials, with the choice of deposition apparatus depending on the specific material:

Tools: Special apparatuses are designed for coating of machining, forming and machine tools. These apparatus are designed to provide high hardness and wear resistance.

Glass: For glass coating, apparatus with fast suction is used, which is important to remove excess gases and achieve a clean coating. This process improves the optical and protective properties of the glass.

Plastics: Coating plastics requires low temperatures and a fast process to avoid deformation of the material. PVD coatings on plastics provide improved scratch resistance and a decorative appearance.

Thanks to different technologies and apparatus, almost any material can be coated as long as the appropriate technology is used, allowing the process to be adapted to the specific needs of different industrial applications.

#5 How thick are PVD coatings?

The thickness of PVD coatings is generally in the micrometer (µm) range. For conventional engineering tool coatings, thicknesses between 0.5 and 5 micrometers are typical. For decorative or optical applications, the thickness of coatings can be in the order of hundreds of nanometres. Conversely, for specialty applications, coatings can be over 10 micrometers thick.

In general, the adhesion of the coating to the substrate decreases with increasing coating thickness. Therefore, for applications that require high adhesion, such as machining or forming, the thinnest layer that still meets the required functional properties is preferred, typically in the range of 2 to 3 micrometers.

#6 Can PVD coatings be applied to all shapes and types of substrates?

Theoretically yes, practically no. The problem with PVD coating is especially the long hollow holes where the coating cannot practically enter. Another limitation is the size, as the process takes place in a vacuum apparatus, which has limited dimensions. The maximum size of the coated parts is therefore determined by the size of the vacuum chamber.

In terms of shape, the effectiveness of the coating depends on the type of equipment. For example, a maximum of five pieces of A4 glass can fit into a drum machine, whereas a flat machine allows a more efficient process. The shape of the part therefore has a major impact on the cost of coating. For coating 2D objects such as glass or sheets of paper, flat equipment is more suitable. Conversely, coating very large parts will require a large platen, which reduces the efficiency of the coating process. For hard coatings, objects with relatively compact dimensions, where the height, width and thickness are approximately the same, are most suitable.

#7 What are the types of PVD technologies?

The most common PVD methods include arc deposition and magnetron sputtering.

Magnetron sputtering works on the principle of atom-by-atom dusting of material from targets in the plasma. The target material is bombarded with argon ions, which leads to the release of atoms that subsequently hit the substrate.

Arc deposition Arc steaming differs in that it creates an arc discharge on the target, which vaporizes the material in larger groups, which can lead to the formation of droplets.

A table showing the advantages, disadvantages and suitability of HiPims, arc steaming and magnetron sputtering can be found on our website PVD Technology. 

#8 How does PVD coating affect surface roughness?

PVD coating hardly changes the surface roughness because it covers the surface atom by atom. Think of it like a thin layer of snow on a mountain. If the surface was polished before coating, it will remain beautifully polished afterwards. If the surface has been sanded or had some roughness, it will have the same roughness after coating.

Therefore, the use of PVD coating cannot be expected to improve the surface quality.

#9 What is the best surface finish in PVD coating for injection moulding?

There are two main strategies for improving mould release:

Sandblasting and coating: This method is ideal if you are working with plastic that is not too flowable or if you are using lower injection pressures. Sandblasting produces a rougher surface which aids in mold release.

Polishing and coating: This method is suitable if you have plastic with good flowability and use high injection pressures. By polishing, you achieve a smooth surface that makes it easier to release the mouldings.

In general, you need to test and find out what chemical interaction between plastics and coatings is best, as there is no one-size-fits-all solution. For example, a CrN (chromium nitride) coating is often better than steel alone, but there may be better PVD coatings for specific applications.

#10 What are DLC coatings?

DLC coatings are special types of PVD coatings based on carbon. The acronym DLC stands for "Diamond Like Carbon". These coatings combine the properties of diamond, such as hardness and durability, with the low-friction, self-lubricating properties of graphite.

By combining graphite and diamond, we create a structure that is both strong and low friction. DLC coatings include a variety of coatings: some are made purely of carbon, others of carbon and acetylene, and some are doped with various metals.

Choosing the right DLC coating depends on the specific application. Some DLC coatings are suitable for use with oil, others without. Some are used for aesthetic purposes, while others provide protection against abrasion or corrosion.

#11 What are the types of DLC coatings?

DLC coatings can be primarily divided into doped and undoped:

Doped with DLC coatings: In addition to carbon and residual gases such as hydrogen, these coatings contain metal atoms such as tungsten, chromium or titanium. These metals form carbides in the coating, which provide additional mechanical or chemical properties useful in specific applications.

Undoped DLC coatings: These coatings contain pure carbon in the form of TAC (Total Active Carbon) or ACH (Activated Carbon High). TAC and ACH have very good non-stick properties but react poorly with lubricants, for example. Undoped DLC coatings are characterized by high hardness and low friction, making them ideal for applications where adhesion and wear need to be minimized.

Choosing the right type of DLC coating depends on the specific requirements of the application, such as the need for wear resistance, chemical stability or interaction with lubricants. Learn more about our DLC coatings.