“We are revolutionizing the coating of ultra-high-strength steels with vacuum technology”

With a new groundbreaking vacuum coating process, the SMS group presents itself as a technology leader in vacuum coating of steel strips for the most demanding applications. In their unique pilot plant in Karlstein am Main, the plant manufacturer is developing innovative Physical Vapor Deposition (PVD) processes together in a joint venture with SITIZN Group Holding AG called NEOVAC, breaking through the previous limits of conventional coating processes. In an exclusive interview with heat processing, Dr. Holger Behrens (Executive Vice President Flat Products, SMS group), André Herzog (CTO NEOVAC) and Tim Ovelgönne (CEO NEOVAC) present their revolutionary technology and its potential for industry to a broader public for the first time.

hp: After three years of intensive development work, you are now publicly presenting your vacuum coating technology for the first time. What convinced you that now is the right time?

Dr. Holger Behrens: For significant developments, it’s important for us to master the technology safely and to have worked out the physical relationships before approaching customers and the market. In the last two years, we have carried out various tests for strip coating of steel strip on our pilot plant and achieved very good and reproducible results. Therefore, we are now able to coat test material from interested customers and demonstrate the possibilities of this process. We offer the advantage of performing surface coatings with zinc using a continuous process for strip widths up to 650 mm.

hp: What challenges of classical coating technology have you addressed with your new plant?

Tim Ovelgönne: We have simultaneously solved two fundamental problems of conventional galvanizing. For ultrahigh- strength steels with 1200 to 1900 MPa tensile strength, both hot-dip galvanizing and electrolytic galvanizing fail. In hot-dip galvanizing at 460 °C, the material properties can change negatively – the steel loses tensile strength. In electrolytic galvanizing, hydrogen can form due to the process, which can lead to material embrittlement. Our vacuum coating process runs as a “cold process” below 200 °C. This allows us for the first time to coat high-ly sensitive steel alloys without negatively affecting their properties.

hp: What makes your vacuum coating technology so revolutionary compared to what already exists?

André Herzog: The decisive factor is the quasi-cold coating, which enables complete decoupling of thermal material treatment from coating. Due to the low thermal input of the coating process, the material properties of the coil are no longer changed. The coating works similarly to a very precise painting process: The steel strip first passes through wet cleaning and is then introduced into vacuum. There, the actual vacuum process starts with plasma pretreatment for fine cleaning of the strip. Subsequently, a pre-coating is applied by magnetron sputtering, comparable to a primer. The decisive step is thermal evaporation: Zinc is liquefied and applied in a controlled manner from the vapor phase via a nozzle system. Like water vapor condensing on a cold mirror – only precisely controllable.

hp: That sounds very complex. Can you describe the practical process in your plant?

Herzog: In our pilot plant, an uncoated coil is introduced into the vacuum system, the chamber is closed and evacuated. On a production scale, this step can naturally also happen inline to enable a continuous process. Then the three-stage coating process of the steel strip takes place in a continuous process – plasma cleaning, pre-coating, zinc coating. A key point here is the Plasma-Enhanced-Evaporation we developed, a novel vapor deposition process with which layer properties can be specifically influenced. Subsequently, the strip is wound up again, the system is flooded and the coil is removed. When working in shift operation, it is possible to coat 5-6 coils in 24 hours, with up to 5 tons per coil.

hp: Aren’t there already PVD processes on the market? How does your approach differ?

Ovelgönne: There are already commercial PVD processes like Jet Vapor Deposition, but they are not designed for ultra-high-strength steels. Our plant has already successfully coated metal strips with tensile strength >1,500 MPa. We developed the process from scratch: How the process stages are connected in series, how we organize evaporation, how pre-coating proceeds – that’s our specific know-how. The process is therefore very interesting for ultra-high-strength materials and also forming steels with high requirements for corrosion protection and surface quality.

hp: But why ultra-high-strength steels specifically? How did you come to this special market segment?

Dr. Behrens: The impulse came from partners in the steel industry. They pointed us to a problem in galvanizing high-strength steels with, for example, martensitic microstructures. Especially with these steel grades, the mentioned disadvantages and limitations such as softening and embrittlement can occur. Furthermore, the user market, i. e., steel processors and press shops as customers of our customers, naturally provides additional impulse for our development priorities. Automotive manufacturers, for example, use sheets of a certain quality with complex properties – from this we derive what technology our customer, the steel manufacturer, needs. Our process is suitable for the steel grades just mentioned as well as other steels and metals.

hp: That sounds logical, but surely implementation wasn’t easy. What technical challenges did you have to overcome?

Ovelgönne: A central challenge is the temperature gradient: The zinc is evaporated at over 600 °C, but the strip remains below 200 °C temperature. With such a high temperature gradient, the layer must be applied very quickly and in a controlled manner. We must achieve directed layer growth with defined grain sizes so that during later forming of the sheets, the layer adheres completely and doesn’t break – otherwise the required corrosion protection wouldn’t be sufficiently provided.

Herzog: Through collaboration at our joint venture NEOVAC, we brought together a steel plant manufacturer with a vacuum technology specialist – that’s actually diametrically opposed, but we created a technology with which we take 

an important step toward quality. The joint venture has two extremely strong partners behind it: SMS as an expert in plant construction and the know-how of SITIZN group Holding AG with several decades of experience in vacuum technology.

hp: If I understand correctly, your pilot plant with 170 tons weight and 15 meters height is quite impressively dimensioned. Was this size planned from the beginning?

Ovelgönne: Within three and a half years, we designed, built and commissioned this plant with our expert team. From the very beginning we wanted to create a scale that meets industrial size requirements and can produce test material for customer applications such as automotive press shops. Our plant can continuously process and coat steel coils with tensile strength up to 1900 MPa and length up to 1000 meters and width up to 650 millimeters.

hp: Those are impressive dimensions. What layer thicknesses and properties do you achieve with it?

Dr. Behrens: We operate starting at 1 μm between approximately 3 to 30 micrometers – for many vacuum processes, these are rather thick layers. The vapor-deposited layer can consist purely of zinc or be supplemented with other metals such as aluminum or magnesium depending on the application. The Pilot plant is designed to produce one-side or double-side coatings.

hp: You focused on zinc – is the technology also interesting for other coating materials?

Herzog: Definitely. The evaporator in our plant is basically a variable “steam cooker” that can be adapted to various metals. For high-melting materials, we need other evaporation sources; this knowledge and experience is available at NEOVAC. The plant is modularly constructed – we can adapt it for specific products depending on partnership and customer requirements. Additionally, through the installed sputtering/ cathode sputtering process, we have the possibility to specifically optimize layer properties.

hp: Why should a steel manufacturer specifically choose your technology?

Dr. Behrens: We offer the market an alternative to a similar but licensed process. Our process enables vacuum coating of ultra-high-strength steels with zinc without license binding.

hp: How does it look energetically – what advantages does your process offer?

Dr. Behrens: We see an energetic advantage in our process compared to known processes like hot-dip galvanizing or electrolytic galvanizing. Creating vacuum and evaporating material consumes less energy according to our analyses. We speak of energy savings of up to 30 % compared to conventional processes, depending on the application. Since the plant operates without combustion processes and runs purely electrically, no CO₂ is produced during operation. When using green electricity, for example, the CO₂ footprint is very small. In comparisons, we must consider what system boundaries we draw, but basically the operating costs, especially energy consumption, are lower.

hp: Currently you are actively seeking strategic partners to test exactly these possibilities – what do you offer concretely?

Ovelgönne: We offer potential partners the chance to do something here where they would normally first have to build their own laboratory system over years before they can test anything. That’s not necessary here – they can send us their sample material and define the desired coatings they need after coating by us for their further material and product tests. We are open to interested parties and welcome them gladly.

hp: Can interested companies visit the plant?

Dr. Behrens: Of course, our pilot plant is open to interested companies. The NEOVAC technology center is located near Frankfurt am Main and is therefore very accessible logistically. It’s important to us to come into contact with interested parties who want to further develop this new revolutionary technology with us.

hp: After three years of intensive development work – what is your initial interim conclusion?

Ovelgönne: We have proven that the technology works; now it’s about scaling and market penetration. For the end market, we need a partner who will now take the next step with us according to their industrial challenges.

Dr. Behrens: We have created something that offers completely new possibilities. With this type of plant technology, one can conduct pre-series and preliminary tests – and this on a scale that is of great interest especially with regard to high and ultra-high-strength steel grades. That’s the asset we offer. We are ready for the next stage of development with the right partners and look forward to everyone who wants to shape the future of steel coating with us.

Dr. Holger Behrens – Executive Vice President Flat Products, SMS group GmbH: Dr. Holger Behrens is responsible as Executive Vice President at SMS group for the Flat Products division. His expertise encompasses rolling mill and strip treatment technologies such as hot and cold rolling, annealing and coating. With his studies at Ruhr University Bochum, Dr. Behrens brings technical basic training that he deepened over years in industrial practice at SMS group.

André Herzog – Chief Technology Officer (CTO) NEOVAC: André Herzog brings decades of expertise in vacuum and cleanroom technology into the partnership with SMS group as CTO of NEOVAC. His career is characterized by the development of high-precision coating processes and practical implementation of complex vacuum processes. At NEOVAC, Herzog is responsible for technological advancement of PVD processes (Physical Vapor Deposition) and their adaptation to specific requirements of steel coating.

Tim Ovelgönne – Chief Executive Officer (CEO) NEOVAC: Tim Ovelgönne has international education from renowned INSEAD and additionally brings strategic competence in Mergers & Acquisitions through his function as Chief Expert M&A at SMS group. His engagement in various companies like A-zero GmbH, CATALYTIC Power Solutions GmbH and NEOVAC GmbH shows his expertise in identifying and developing innovative technology companies.