The process
For PVD coating, high-purity, solid metals are used as layer materials. Depending on the desired properties of the coating, these metals may be, for example, titanium, aluminium, or chromium, as well as zirconium and silicon. This material is referred to as the target.
The composition, thickness and properties of the coating can be controlled by the selection of the target, the process parameters, and the deposition conditions. This allows regulation of such factors as the structure and hardness of the workpiece, and also its thermal resistance.
The desired coating thickness furthermore depends on the size and purpose of the workpiece. In principle, the coating can be up to 10 μm thick. For micro tools, on the other hand, the coating thickness is usually less than 1 μm.
There are different PVD coating methods, and these can also be combined. Those most commonly used are:
- Arc-PVD: During arc evaporation, an arc is created between an electrode and the coating material in order to detach particles from the target.
- Sputtering: The target is bombarded with magnetically deflected ions or electrons
- Laser: Laser beams are fired at the material in order to initiate evaporation.
At Härtha, we offer sputtering and arc coating. In principle, the different techniques all follow the same sequence of steps.
Evaporation
During evaporation deposition, the target is heated so much that the atoms on the surface are released as gas, and thus become available for the next step. Different techniques can be used to accomplish this. At Härtha, we use the arc technique.
To ensure controlled conditions and prevent interaction with air molecules, evaporation takes place in a vacuum.
Reaction
To deposit the evaporated material onto the workpiece surface, a reactive gas is now supplied, and this combines with the metal vapours. The choice of gas has an important influence on the properties of the coating. Generally, the gas of choice is either a gas containing carbon or nitrogen. These gases deliver strong adhesion, and form nitride and oxide compounds that protect against rust and corrosion.
In order to prevent unwanted chemical reactions, this step takes place in a chemically non-reactive atmosphere. This can be achieved by using an inert gas such as argon. To ensure that the coating thickness is uniform across the entire workpiece, the workpiece is rotated about multiple axes during this step.
Deposition
In the final step, the evaporated atoms of the target condense on the workpiece surface, forming a thin film coating.
Wear-protection coatings at a glance
PVD coatings are suitable to function as wear-protection coatings. Frequently used basic types include titanium nitride, titanium carbonitride, and titanium aluminium nitride.
An overview of coating systems and their properties can be found in our table.
Areas of application
PVD coatings are used across a multitude of industries and for a wide variety of components:
- Cutting tools
- Forming and shaping tools
- Plastic moulds
- Industrial components
- Automotive components
- Jewellery and watches
- Medical engineering
- Decorative and sporting applications
- Aluminium die casting
Suitable materials
PVD coating is a surface treatment. To prevent changes to the microstructure and hardness, and to ensure dimensional stability, the material must be subjected to a heat treatment appropriate to the coating.
Since PVD coatings can be applied below 500 °C, the process is highly suitable for high-speed steels, hot worked steels, and some cold worked steels.
Even steels tempered at very low temperatures are generally suitable for coating – with special coating systems for low-temperature processes (between 250 °C and 450 °C).
Advantages and benefits
The key advantages of PVD coatings at a glance:
- Great dimensional stability thanks to low coating thickness
- High adhesive strength
- Increase in wear resistance and hardness
- Reduced friction, thanks to smooth surfaces
- Coating temperature up to 450 °C
- Any type of layer structure (mono-layer, multi-layer)
- Visual refinement
Processing options
At Härtha, we offer you the PVD coating and DLC coating processes. We coat workpieces of different sizes, from the micro range to a diameter of 500 mm. In addition to standardised coatings, we also develop tailor-made solutions that will fit your specific application.
Standard test procedure
We inspect all PVD coatings visually. If you require an in-depth test, we can recommend non-destructive testing methods.
Customer information
Before we can quote you an offer for PVD coating or find a different coating solution for you, we need you to provide us with the following information first:
- Purpose of application
- Material designation
- Thermal pre-treatments
- Desired coating thickness in µm
Process locations
Find a location near you. Our location overview shows you which Härtha locations offer PVD coating and which other metalworking processes we provide.