- Improved Graphit-iC and MoST coating formulations able to work at combined rolling-sliding line contacts loaded up to 1,6 GPa, with sliding speed up to 7.6 m/s and specific lubricant film thickness as low as 0.08-0.10, have been developed by TEER. At pure rolling tribological contacts MoST coatings are able to bear hertzian pressures up to 3 GPa with an excellent fatigue resistance. Moreover, these coating materials can be used in combination with oil lubricants free of toxic and environmentally unacceptable extreme pressure (EP) and anti-wear additives.
- A new TiCx-based coating material has been also developed. These coatings exhibit good wear resistance at very low specific lubricant film thickness (0.05 at 1.46 GPa of hertzian pressure). However, TiCx-based coatings need EP and anti-wear additives in the fluid lubricant. Otherwise, their functional performance falls dramatically.
- Combining parts coated with a self-lubricant material based on MoS2 and an oil-air lubrication systems, where oil is added periodically to an uninterrupted air stream, a new generation of ballscrews for machine-tool applications have been developed by SHUTON. These new ballscrew systems are able to reach a D*N factor up to 120.000 mm*rpm.
Prototype gearboxes containing gears coated with Graphit-iC and MoST coatings are available. These gearboxes are able to run with a significantly reduced amount of lubricant fluid without any additional risk of adhesive wear or metal-metal seizure.
Usually heavy loaded motion transmission systems, like gearboxes and ballscrews, avoid risk of metal metal contact failures by supplying to the system an excess of hydraulic fluid. However, a such quantity of lubricant is only need for the most critical situations of the mechanical system life, namely, when motion is starting or stopping, and the elastohydrodinamic lubrication regime is not stable. Otherwise only a low percentage of the usual lubricant amount is enough to prevent wear and part damages. On the other hand, if the lubricant fluid is significantly reduced, several benefits can take place. For motion transmission systems running at high speed an excess of fluid involves frictional resistance and it limits the maximum effective working speed of the mechanical system. In all cases, hydraulic fluids are a major source of waste generation and imply expensive disposal costs. The aim of the project is to reduce dramatically hydraulic fluids used for loaded motion transmission systems by saving lubrication failure risks by mean of low friction high resistant coatings. At present there exist MoS2/metal, Diamond like carbon and TiC coatings able to carry out this job. They are already being used ;n the aerospace industry and recently start to be applied for cutting and forming tools. The proposed approach of the project is to evaluate their performance for this new potential field of application using laboratory simulation tribological tests and practical tests on real parts. Then specific coating solutions will be developed for those systems where presently available products were nor resistant enough.
Funding SchemeCRS - Cooperative research contracts
DY10 4JB Kidderminster,hartlebury