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Beyond Surfaces #5 - Coatings

“The surface is always a complex matter because it is subject to so many influences”. In the latest edition of BEYOND SURFACES, Professor Paul Mayrhofer at TU Wien explains why this was a challenge even for renowned physicists such as Wolfgang Pauli – and demonstrates the best way to tackle the problem together with other experts in the field of surface technologies.

Find out how these technologies help make our cars faster and use resources more sparingly. And how customers around the globe rely on our solutions to create more efficient and sustainable production methods. In addition, our laser cladding expert Dr. Arkadi Zikin talks about the new appli- cations of this technology and presents a brand new research project with ETH Zurich. Immerse yourself in the fascinating world of coatings.

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Prof. Paul Mayrhofer on materials and surfaces

Researchers like Paul Heinz Mayrhofer make significant contributions to the expanded use of intelligent coatings in industry. During a visit in Vienna, the materials scientist explained what this is about and the role of Oerlikon Balzers in this area.

Without materials science, there wouldn’t be any technology. The development of mankind has always been linked to materials. There’s a good reason why entire epochs are named after them: Stone Age, Bronze Age, Iron Age, ...

Vienna, Technical University, Getreidemarkt 9. It is a cold Tuesday in March, nine o’clock in the morning and Univ. Prof. Dipl.-Ing. Dr. mont. Paul Heinz Mayrhofer is punctual. He is a friendly man with a youthful demeanor, who listens benevolently and answers patiently. Mayrhofer mentions that he has office hours at around noon and a lecture at 2 p.m.: “Shall we?”

Indeed, we shall. There is a good deal to see and even more to discuss.

Professor Mayrhofer is the director of the materials science research department at the technical university in Vienna, known as the TU Wien. He studied in Leoben in Styria and has researched in the US state of Illinois, in Sweden and in Aachen, Germany.

Mayrhofer is a specialist in hard coatings. He has received a series of awards for his work. In 2011 the prestigious Christian Doppler Research Association awarded him a seven-year laboratory grant, which he is completing this year at TU Wien.

We have just arrived in a basement room in which a part of the Christian Doppler Laboratory, Application Oriented Coating Development, is set up. It is supported by Oerlikon Balzers and the Tirolean Plansee Group, which manufactures powdered metallurgical materials. Nestled between colorful hoses, wires and gray cabinets stand numerous pieces of equipment to which Mayrhofer and his students have given female names. One is called Angie, another Ylvi, and another is named Noreia after the Celtic goddess of ore.

Mayrhofer displays a cathode made of tantalum. The material is atomically evaporated in the equipment using a high input of energy. The method employed is called Physical Vapor Deposition (PVD). The particles which are thereby released attach themselves to the materials and elements in their proximity. If they should happen to come into contact with drills, spindles, piston rings or the like, these objects are given a coating which can be significantly thinner than a human hair and nearly as hard as a diamond.

The largest piece of equipment that the professor and his staff use for research purposes is called INNOVA and has been provided by Oerlikon Balzers. It is located in the old quarters of the TU on Karlsplatz at a distance of five minutes on foot.

Room ACEG31. There is a sign outside: PVD Laboratory. Inside stands a squarish box that looks like a monstrous oven with soot-covered heating coils. Up to six cathodes with different materials can be employed in the INNOVA. The material is transformed into a vaporous state by means of an arc evaporation process, but also using cathode sputtering. The trajectory of the ions can be controlled using electromagnetic coils. This helps them find the right place to attach themselves. The professor says: “You need to have an exact understanding of the materials right down to the atomic level.”

More on this follows in Mayrhofer’s office. There are models of crystals on the cabinets. The wall is adorned by a large whiteboard with a sketch consisting of chemical abbreviations, letters and numbers, all connected by circles and arrows.

Prof. Mayrhofer, would you let us in on the secret behind the formulas on the board?
We are currently dealing with tungsten carbide and tungsten nitride. The idea is to incorporate tungsten in a hard, firm layer. On contact with a sulfurous environment and high pressures, it develops a lubricant. Its effect would be comparable to that of molybdenum sulfide.

Essentially, you create materials that do not exist in that form in nature, right?
That’s right. Our objective is to develop materials with higher strength and greater toughness, but also improved thermal stability. Usually, however, these properties are mutually opposed. When you improve the hardness of a material, it is usually at the cost of lower toughness. And vice versa.

And what would be an example for a layman?
Gold is a soft metal, as we know, which can be deformed very easily. A knife made of gold would make no sense because it would be dull after the first cut. That doesn’t happen with a ceramic knife. However, the ceramic knife would break immediately if it fell to the ground. So we look for combinations utilizing the strengths of materials so that their drawbacks can be compensated.

Why did you choose a profession like this?
In my school in Burgenland, Austria, we took a career aptitude test in the 8th grade. It indicated that I should pursue a technical profession. A cousin of my mother was a shop teacher at the polytechnic school in the city of Eisenstadt. He was of the opinion that I should choose materials technology as my field of study. A number of teachers at the polytechnic school came from the university for metallurgy and mining in Leoben where I then studied materials science.

What’s so fascinating about materials science?
Without materials science, there wouldn’t be any technology. The development of mankind has always been linked to materials. There’s a good reason why entire epochs are named after them: Stone Age, Bronze Age, Iron Age, …

In what materials epoch are we living today?
As a materials scientist, I would have to say: in the Silicon Age. Silicon is a semiconductor, so we could also say the Semiconductor Age. However, for communications in the modern world, i. e. for smartphones, computers, laptops and so forth, you also need rare-earth metals. This is still a relatively unknown field.

Which materials are the special focus of your research?
A class of materials that I have dealt with throughout my career is that of the nitrides. They are the chemical compounds which result when nitrogen combines with metals. A compound with which my name is connected worldwide is titanium aluminum nitride.

Which materials might be of significance in the future?
What has been moving into focus more and more of late are the borides, or chemical compounds of boron with metals which display ceramic properties. They are even harder than nitrides, but, naturally, are also much more brittle.

Materials consisting of two elements, such as binary nitrides, carbides or borides, are considered to be well researched. What potential do materials consisting of three or more elements have?
We refer to these as ternary, quaternary or multinary compounds. These allow considerable improvements in material properties. At the same time, the complexity involved in the development of multinary systems like these is greater. Put differently: It takes much longer to thoroughly research and understand these compounds.

For example?
Titanium nitride is a common compound of two elements that has been in use now for a long time. The disadvantage: It forms a porous oxide layer. But if aluminum is added to the titanium and the nitrogen, the material properties change significantly. Aluminum also forms an oxide layer, however it is stable and dense. Titanium aluminum nitride is a material which develops higher strength when stressed through temperature or mechanically, making it especially suitable for drilling, cutting or milling tools.

If you combine all of the known elements, the possibilities are innumerable.
That’s right, the permutations result in millions of approaches. As a researcher, you are faced with questions your whole life long and it never stops, especially with coatings. The surface is always a complex matter because it is subject to so many influences. The physicist Wolfgang Pauli used to say, “God made the bulk; surfaces were invented by the devil.”

You have an INNOVA from Oerlikon Balzers in your lab. What do you use it for?
We use the INNOVA to ensure that our process development is as industry oriented as possible. The objective is resilient, stable coatings. As we do so, we work with fundamental aspects of research findings. What works. Where and how it works. What spectrum of possibilities exists. We also use complex computer simulations with which the properties of the coatings can be calculated at an atomic scale and thereby improved. Oerlikon Balzers specialists then refine our findings for customer applications.

How would you evaluate the interaction between research and industry in general?
Research and industry go hand in hand. Research needs the applications from industry. Industry needs the findings and knowledge from research. The two are inseparably connected.

You are the academic dean for mechanical engineering, industrial engineering and materials sciences. Can you comment on the added value of this interdisciplinarity?
Take a turbine, for example. In it, the materials operate at their limits. The turbine blade must be exceptionally tough; it must not break under any circumstances. At 1 300 degrees Celsius, of course, it needs a ceramic coating. That is materials science to the max. Mechanical engineering supplies the technical framework. And the industrial engineer has to ensure that the turbine can be produced cost effectively. For it all to work, everyone needs to understand all the others.

Back to materials science. If I were to compare the field with a world map, is everything known and charted or are there still blank spots?
My gut feeling says there are still many blank spots. In our field, we tend to be at the beginning of the discoveries because we don’t even know most of the element combinations yet.

Where does research stand? Are we still at Marco Polo or already at Christopher Columbus?
Neither one. With reference to materials science, we only know parts of Europe. With regard to all the other continents – to keep with the metaphor – we probably don’t even know they exist.

A flexible all-rounder for ambitious uses

NNOVA is the preferred coating system size for most production requirements and is perfectly suited for small to large quantities. It is the all-rounder for PVD coatings.
The name INNOVA has become a synonym for performance, reliability and versatility.

Find out more about INNOVA:


Petra Ammann

Petra Ammann

Head of Communications Oerlikon Balzers

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