Low friction is a key prerequisite for a wide range of technical applications. In many systems, reducing the friction and increasing the lifetime of tribological contacts is essential to improve efficiency, minimize wear, and ensure reliable operation under demanding conditions.
The objective of this ESA-founded project is to investigate the influence of different surface modifications on friction and to evaluate their potential for enhancing tribological performance. In particular, the effect of laser structuring the substrate before applying a dry lubrication coating by plasma coating is assessed.
Experimental
Test samples are prepared by laser surface texturing (LST) and plasma vapour deposition (PVD). The obtained structure is verified by electron-microscopic methods (SEM/FIB) and white-light interferometry (WLI), the tribological performance by Pin-on-Disc measurements.
The following steps are identified to optimize the performance of PVD coatings:
- Optimization of the sample cleaning process performed by plasma etching.
- Optimization of coating adhesion: application of appropriate interlayer.
- Optimization of tribological performance: apply dry lubrication coatings with different thicknesses.
In parallel, the process of laser surface texturing is developed. To obtain a useful structure, several development loops are required to assess different structures such as dimples, lines, and grids with different periodicities and structure depths.
Results
Pin-on-Disc tests are performed under vacuum conditions and indicate very promising results:
- The low friction coefficient indicates a proper solid lubrication
- The lifetime of the structured samples exceeds the lifetimes observed for flat references (considering the reduced contact area)
When applying the same treatment on the complex shape of harmonic drive gear components, the positive results could not be reproduced: Further development steps are required to identify the root cause and to optimize the surface treatment accordingly.
Applications
For setups offering tribological contact surfaces with moderate complexity, the developed surface functionalization may be a promising step towards prolonged lifetimes.
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