Diamonds aren’t just a girl’s best friend - they also boast outstanding physical properties that makes them an ideal material for industrial applications such as cutting and polishing. It is extraordinarily hard, conducts heat well and is practically inert to chemical substances. Ceramics – particularly high-performance ceramics – are likewise able to demonstrate special qualities. They are robust and withstands high temperatures. Researchers have now created a diamond coated ceramics composite material that combines the best of both materials.
Dubbed DiaCer, the new material offers maximum wear-resistance coupled with low values of friction making it ideal for components and tools that are subjected to heavy strain, such as in pumps or forming and shaping dies. Created by scientists from four Fraunhofer institutes, together with industry partners, the basis of the new material is a modified silicon-nitride or carbide ceramic.
To craft the ceramics so that the diamond coating adheres firmly and evenly to the base body the researchers initially placed the components and tools in a vacuum reactor for the hot wire chemical vapor deposition (CVD) technology applied for the coating process. Next, the researchers add methane and hydrogen. In order for the diamond coating to grow, wires are spread at intervals of just a few centimeters across the objects that were going to be coated. The wires are heated until they reach incandescence. This activates the gases; carbon is deposited on the surface in crystalline diamond form.
“Using our process, we can apply a diamond layer of up to a half square meter in size," says project coordinator Dr. Lothar Schäfer of the Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig. ”There‘s nothing else like it in the world."
DiaCer is already proving its worth in tests. With axial face seals that EagleBurgmann Germany inserted in pumps for critical environments, like the conveyors for oil, sand and gas mixtures, the diamond coating extends the durability for each application by a factor of 4 to 1,000. The test tools, which are used in production at the Elisental wire plant for example, were barely worn after several tons of wire had been produced.
Axial face seals for pumps have since been coated with diamonds by Condias GmbH - a spin-off of the Fraunhofer Institute for Thin Films and Surface Technology - and marketed by EagleBurgmann in a variety of complex applications. The researchers say many other applications are also conceivable. “Ultimately, DiaCer is of interest for all components in machine construction that need strong resistance to wear," summarizes Schäfer.
In recognition of their achievement, the interdisciplinary team responsible fort he new material has been awarded the Stifterverband Award for Science – a 50,000 euro prize awarded for scientific excellence in applied research projects carried out jointly by Fraunhofer Institutes and business enterprises and/or other research organizations.