Tribology Innovation Center Dresden (TICD)

Tribological Coatings and Surfaces – Expertise in Friction Reduction and Wear Protection

TICD focuses on the development of friction-reducing coatings and surfaces for a wide variety of applications, for which Fraunhofer IWS and TU Dresden conduct joint research.
© Fraunhofer IWS
TICD focuses on the development of friction-reducing coatings and surfaces for a wide variety of applications, for which Fraunhofer IWS and TU Dresden conduct joint research.

In times of global efforts to reduce climate-damaging CO2 emissions, the issue of friction often plays an underestimated role. After all, up to 20 percent of the primary energy used in a wide variety of vehicles, machines and systems is unnecessarily lost due to friction. In addition, there is the problem of tribological wear of tools and components, which limits the service life of systems in many applications or causes downtimes and maintenance times and results in high resource consumption.

In the Tribology Innovation Center Dresden (TICD) Fraunhofer IWS together with the TU Dresden researches tribological basic phenomena as well as suitable tribological measures, especially through coatings or other surface modifications. The goal is a significant reduction of friction and wear, whereby the solutions found should be as universally applicable as possible. Attention is paid to ensuring that the technologies developed are suitable for series production and can be used directly in the production of components and tools. 

Friction-reducing Diamond-like Coatings

Mit ta-C beschichtete Kolbenringe, mit denen die Reibung in Motoren um bis zu 50 Prozent abgesenkt werden kann.
© Fraunhofer IWS
Piston rings coated with ta-C, which can reduce friction in engines by up to 50 percent.

The focus is on the so-called ta-C layer (tetrahedral amorphous carbon), the hardest variant from the group of diamond-like carbon (DLC) layers. Structurally and chemically, it combines extremely high hardness with very low friction under almost all conditions. This combination predestines the ta-C coating for numerous applications of components and tools in a wide range of industries.

The Laser-Arc process for ta-C coating developed at the Fraunhofer IWS is now industrially established and is used in the series production of ta-C coatings. A fundamental problem is the particle-induced roughness of the coatings. Currently, work is being done on a new generation of plasma filters to deposit almost defect-free ta-C coatings.

Several projects are dedicated to supra-low friction with ta-C layers. For this purpose, solutions are being developed that transfer the phenomenon of supra-friction, which has so far only been observed in the tribometer, to mechanical engineering applications (CHEPHREN, SUPRASLIDE).

Coating systems based on ta-C with various dopants (ta-C:X) are also being produced for critical ambient conditions (dry to vacuum). Here, a combination of ta-C with the solid lubricant MoS2 is proving particularly promising. Suitable hybrid coating systems are being developed in the LUBRICOAT project.

 

PVD Wear Protection Coatings

Mit ta-C beschichtete Vielzahnfräser zur Bearbeitung besonders abrasiver CFK-Verbundwerkstoffe.
© Fraunhofer IWS
Multi-tooth cutters coated with ta-C for machining particularly abrasive CFRP composites.
Mit AlTiN/TiN beschichtete Werkzeugschneide mit »Selbstschärfungseffekt« beim Schichtwachstum.
© Fraunhofer IWS
AlTiN/TiN coated tool cutting edge with "self-sharpening effect" during layer growth.

Several coating technologies are being further developed at Fraunhofer IWS to make surfaces of components and tools resistant to wear in different application areas.

PVD technologies are particularly suitable for this purpose, such as the Laser-Arc process for superhard ta-C coatings or further developments of the classic DC-Arc process for nitride hard coatings. These allow, among other things, the self-sharpening coating of tool cutting edges and the deposition of coatings up to 100 micrometers thick for particularly demanding applications. In addition to the established high-performance coatings (metal nitrides and nanocomposites), research is currently being conducted into coating systems based on high-entropy alloys (so-called HEL nitrides) to further improve coating performance. Advantages in terms of temperature resistance are expected here, which would allow higher cutting speeds, for example. 

Laser Cladding and Thermal Spraying

Thermisches Beschichten eines Hydraulikzylinders mittels Laserauftragschweißen.
© Fraunhofer IWS
Thermal coating of a hydraulic cylinder using laser cladding.
Thermisches Beschichten einer Walze mit glatter Hartmetallschicht mittels HVOF-Suspensionsspritzen.
© Jürgen Jeibmann
Suspension high velocity oxygen fuel spraying (S-HVOF) for smooth ceramics and hard metal coatings.

With buildup welding and thermal spraying, industry-oriented and future-proof systems, processes and coatings are developed in line with economic efficiency and sustainability. Laser buildup welding is a very flexible, process-reliable and economical method of functionalizing surfaces for a wide range of applications in corrosion and wear protection as well as tribology, for example for coating brake discs, hydraulic cylinders or for manufacturing plain bearings. The coatings of metal alloys, hard alloys or carbide-reinforced coating systems are characterized by a fusion-metallurgical bond of highest adhesive strength. The bandwidth ranges from the smallest structures or layer thicknesses at the micrometer level with 100 watts of laser power to high-performance processes with more than 20 kilowatts of laser power and up to 45 millimeters of track width at the highest application rates.

With the process diversity of thermal spraying, functional coatings of polymer, metal, carbide and ceramic can be applied to component surfaces over large areas. In contrast to cladding, adhesion is based on a stable mechanical bond to the component surface, whereby components remain thermally unchanged. Friction and positive adhesion offers a range of material composites, from a single layer (with a thickness of a few micrometers to several millimeters) to mixed layers and multilayer coatings on components made of metal, polymer or ceramic. Wear protection applications are addressed by suspension-sprayed ceramic and carbide wear protection coatings, which save costs in post-processing due to their quality, plasma-sprayed wear protection coatings on temperature-sensitive components such as fiber-reinforced plastics, and functional coatings, for example for heat conduction or electrical heat generation.

Laser Structuring

Fraunhofer IWS laser-structured ceramic plain bearing.
© Fraunhofer IWS
Fraunhofer IWS laser-structured ceramic plain bearing.

The laser as a tool is capable of shaping the topography of component surfaces with micrometer precision. By means of laser structuring, two- and three-dimensional micro- and nanostructures can be applied and thus the tribological behavior of sliding surfaces can be changed in a targeted manner. This is done either by influencing the wetting and viscosity-related lubricant film structure, the reservoir effect of micro-lubricant film pockets, hydrodynamics or oil conduction structures.

The structuring process can be adapted to the material and surface to be processed by selecting the right wavelength and pulse duration. With the direct-writing process, flexible, freely designed surface structures can be generated. By superimposing several partial beams from a laser source and the resulting periodic interference pattern in the superposition volume, direct laser interference patterning (DLIP) allows the generation of up to one million structures per laser pulse. As a result, it is possible to apply large-area laser-structured surfaces to tribological parts and components, such as bearing washers and piston rings, in a very short time and thus to use the process economically in series production.

Tribological Characterization

Ball-on-disc contact in an oscillating wear tribometer.
© Dirk Mahler/Fraunhofer IWS
Ball-on-disc contact in an oscillating wear tribometer.

In addition to the focus on application-specific coating development and friction minimization, the TICD also conducts extensive research into the fundamentals of tribological characterization. Great importance is attached to reproducing real loads by means of suitable geometries and test parameters. Testing can also be carried out in different atmospheres, including ultra-high vacuum. 

Tribological analysis is accompanied by comprehensive coating and surface analysis. All common methods of basic coating and surface analysis are available at the TICD – from basic mechanical characterization to topography/roughness analysis and adhesion tests, as well as electron microscopy, Raman spectroscopy and X-ray reflectometry for chemical and structural analyses.

A second focus is research on new methods of tribological characterization, tribometry. Current topics are the investigation of the lubrication condition by means of high-resolution measurement of the complex electrical resistance, visualization of time- and spatially-resolved information (triboscopy) and metrological recording of suprashming in geometry similar to the component and close to the application. 

Cooperation partner

Technische Universität Dresden

© TU Dresden
Microstructured metal component to improve tribological properties.
© Fraunhofer IWS
Microstructured metal component to improve tribological properties.
Ion cross section through a multilayer coating system in the scanning electron microscope.
© Fraunhofer IWS
Ion cross section through a multilayer coating system in the scanning electron microscope.

The Chair of Large Area Laser Based Surface Structuring of Prof. Andrés Fabián Lasagni at the Institute of Manufacturing Technology (IF) at the TU Dresden focuses on the development of functionalized surfaces using laser based manufacturing processes, optical devices for industrial scale laser texturing and recently also inline monitoring systems. Within the TICD, Fraunhofer IWS and TU Dresden cooperate in joint public projects as well as in collaborations with industrial partners. Coating with friction reducing carbon layers – in combination with effective laser texturing of the coating – shows great potential for many tribological applications.

Collaboration highlights 

The combination of a hybrid coating of superhard ta-C carbon and the solid lubricant MoS2 togehter with laser structuring using the DLIP process has proved particularly promising. Such high-performance coatings exhibit extremely low friction and virtually no wear even under demanding vacuum conditions.

 

The Chair of Materials Technology of Prof. Christoph Leyens and the Chair of Mechanics of Materials and Failure Analysis at the Institute of Materials Science of Prof. Martina Zimmermann focus on a profound understanding of materials as the basis of their research work in the field of coating production, coating analysis and tribological as well as mechanical characterization. The focus is therefore on elucidating the interrelationship between structure and microstructure as well as the functional properties of materials including layer systems. 

Collaboration highlights

Within the regional research network "DRESDEN-concept", joint research is currently being carried out on several topics, such as tribological surface layer/hard material layer composites with a tribological lightweight construction application background and hard material layers based on so-called high-entropy alloys (HEA). Here, the expertise in PVD coating production, micromechanical characterization with the latest methods of structure and microstructure analysis and comprehensive materials know-how complement each other.

Video: Ultra- and Superlubricity

© Fraunhofer IWS

Ultra-low friction allows friction losses in internal combustion engines to be cut in half compared to current state-of the art. The friction coefficient is between 0.01 and 0.05, which is roughly equivalent to the friction of very smooth steel sliding on ice.

Experts, on the other hand, only speak of superlubricity when the friction coefficient falls below 0.01. To illustrate this, one can imagine a five-ton elephant standing on a plate. If this plate is super-lubricated, a person could push the elephant effortlessly.

Projects

Chephren

Ultra-smooth and super-lubricating coatings for component applications, Timeframe 09/2021–08/2024 (BMWK: FKZ: 03EN4005E)

LUBRICOAT

Vacuum arc deposition of MoS2/ta-C coatings and mechanical-tribological testing, Timeframe 06/2021–05/2025 (BMWK: FKZ: 100582372)

SULUTRIB

Further development of tribometry for research and validation of supra-low friction phenomena, Timeframe 12/2020–11/2023 (BMWK: FKZ: 03EN4006A)

PROMETHEUS

High-performance carbon coatings for friction-optimized engine components, Timeframe 01/2019–06/2022 (BMWK: FKZ: 03ET1609E)

News and Media

 

Press release / 12.10.2021

Superlubricity eliminates friction in engines

Fraunhofer IWS works on machines that barely lose energy in the form of waste heat

 

News / 27.9.2021

Smooth process for high savings

 

Press release / 11.1.2019

Elucidating the Atomic Mechanism of Superlubricity

Tribology: Design Rules for Extremely Low Coefficients of Friction