Fraunhofer Institute for Mechanics of Materials IWMRolling bearings operating under high temperatures and heavy loads represent one of the major challenges in mechanical engineering. Conventional oils and greases fail in these conditions. This project systematically investigated how graphite, as a standalone solid lubricant, can provide long-lasting and reliable lubrication for rolling bearings—from the atomic level to the actual bearing system. The results show that graphite-phenolic resin coatings extend service life by a factor of 50 compared to pure graphite and achieve performance comparable to that of grease lubrication. The project thus paves the way for low-maintenance rolling bearings with lifetime lubrication—a true game-changer for high-temperature applications in industry.
Mechanisms of graphite lubrication in rolling contacts
Completed research project
Project description
Market Demand and Societal Challenge
Rolling bearings are key components in nearly all machines and systems—from wind turbines and electric motors to industrial gearboxes. Conventional lubricants such as oils and greases lose their effectiveness at temperatures as low as approximately 180 °C, leading to wear, unplanned downtime, and costly maintenance. With the trend toward higher power densities, high-temperature processes, and low-maintenance systems—such as in electric mobility or aerospace—there is a growing need for alternative lubrication solutions that function reliably even under extreme conditions. At the same time, sustainability is becoming an increasingly important consideration: lubricating oils containing additives are environmentally problematic and must be replaced regularly.
Project Approach
The project adopted a multiscale approach to investigating graphite as a standalone solid lubricant for rolling contacts—ranging from atomistic simulations and model experiments to system-level tests on real rolling bearings. For the first time, the mechanisms of action of graphite under realistic high-load conditions were systematically elucidated. In the process, structural transformations of graphite into turbostratiform carbon at the friction interface were discovered, and the influence of humidity on the lubricating effect was modeled at the atomic level. In addition, a new class of composite layers made of graphite and phenolic resin was developed and evaluated, which significantly alleviates the service life issues associated with pure graphite layers. As an innovative relubrication solution, a graphite-phenolic resin pin was integrated into the bearing as a sacrificial component.
Contribution to Addressing the Challenges
The project results provide the scientific basis for the development of graphite-based rolling bearings with lifetime lubrication—that is, bearings that can operate for their entire service life without relubrication. In system tests, graphite-phenolic resin coatings achieved a service life of at least 200,000 cycles with friction behavior on par with conventional grease lubrication. This opens up the possibility for industrial users to drastically reduce maintenance intervals, minimize machine downtime, and operate high-temperature applications in a cost-effective and environmentally friendly manner.
Fraunhofer IWM’s Work Packages in the Project:
Using nanoscale simulations, Fraunhofer IWM has established a solid foundation of fundamental knowledge regarding the lubrication mechanisms of graphite, thereby providing insights that cannot be obtained through experimental methods alone.
- A mechanistic explanation of moisture-dependent graphite lubrication behavior.
- Explanation for the transformation of graphite into turbostratic carbon at the friction interface — a phenomenon previously undescribed in the scientific literature.
- Further development of the recognized adsorption model of graphite lubrication — published jointly with the project partners in *Nature Communications* (2022).
- Physical basis for targeted material and coating developments
Based on the project results, Fraunhofer IWM can offer industrial companies the following research and development services:
1. Atomistic simulation of solid lubricants
Fraunhofer IWM performs tight-binding and molecular dynamics (MD) simulations to elucidate friction mechanisms in solid lubricants at the atomic level.
- Atomistic simulation of materials such as graphite, MoS₂, h-BN, or composite materials
- Analysis and visualization of friction mechanisms at the molecular level
- Comparative evaluation of various material candidates
2. Moisture- and temperature-dependent lubricant modeling
The Fraunhofer IWM conducts simulation-based analyses of the influence of environmental conditions on the lubricating effect of solid lubricants in highly loaded contacts.
- Modeling the influence of humidity, temperature, and atmosphere on tribological behavior
- Analysis of lubrication behavior under extreme conditions (vacuum, high temperature, varying climatic conditions)
- Simulation-based design recommendations for specific operating environments
3. Development and Evaluation of New Solid Lubricant Composite Systems
Building on extensive knowledge of graphite-phenolic resin systems, Fraunhofer IWM supports industry partners in the development of customized solid lubricant coatings—from design to characterization.
- Design and simulation of application-specific solid lubricant coatings
- Material Characterization and Tribological Evaluation of Composite Systems
- Optimization of layer structure and composition for defined load conditions
4. Multiscale friction and wear modeling / Digital twins
Fraunhofer IWM employs a consistent modeling methodology that transfers simulation parameters from the atomic to the macroscopic scale— thereby enabling the creation of digital twins of real tribological systems.
- Creation of digital twins of tribological systems based on cross-scale parameter transfer
- Predictive service life forecasts for real components and systems
- Simulation-based design optimization without experimental test series
