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Content archived on 2024-06-18

Formulating an Understanding of Tribocorrosion in Arduous Real Environments – Bearing Emerging Technologies

Final Report Summary - FUTURE-BET (Formulating an Understanding of Tribocorrosion in Arduous Real Environments – Bearing Emerging Technologies)

see attached document (2 page summary.doc)

FUTURE BET is a project funded by through the European Commission FP7 Marie Curie Initial Training Network (ITN) European Industrial Doctorate (EID). FUTURE-BET is an abbreviation for Formulating an Understanding of Tribocorrosion in ArdUous Real Environments – Bearing Emerging Technologies. As the title suggests, this project is all about adding knowledge on tribocorrosion processes within bearings and understanding the future demands on bearings and the industrial landscape changes.
The FUTURE-BET project brings together, as main partners a major bearing manufacturer and world leader in bearing technologies (SKF) and a world leading research group in tribocorrosion (iFS in University of Leeds). As associate partners and supporting these activities are Afton Chemical as a lubricant supplier, Hauzer as a downstream supplier of coating technologies and Volvo as an automotive end user.
The main aim of FUTURE-BET is to provide professional development in the multidisciplinary field of tribocorrosion relevant to the successful operation of bearing technologies across a wide range of industrial sectors. Tribocorrosion, as the name suggests, bridges the tribology and corrosion disciplines; it describes the diverse range of surface/surface, surface/environment, surface/lubricant interactions and processes that can affect the integrity of the engineering system or affect the efficiency of that system in operation. The range of processes occurring to affect bearing operation is large and, as such, to understand tribocorrosion (fully), to the point where this can be incorporated into the bearing system design requires an entirely interdisciplinary approach as is presented in FUTURE-BET. The 5 PhD projects are divided into three Scientific Work Packages (SWPs) as outlined below:
- SWP1 Enabling; Enabling technologies underpin the scientific workprogrammes. New methodologies were developed to monitor tribocorrosion processes in-situ (ESR1) and to assess hydrogen permeation in bearings (ESR2)
- SWP2 Understanding; Understanding tribocorrosion, or indeed the lack of fundamental understanding of mechanistic processes at complex tribocorrosion interfaces is critical if step advances in tribocorrosion management are to be made. Progress has been made in modelling the mixed lubrication regime for the first time (ESR 3) and in developing a semi-empirical approach for incorporating water effects in tribocorrosion (ESR 4)
- SWP3 Solutions; Solutions for bearings emerging technologies have been developed using new lubricant additives and incorporating Physical Vapour Deposition (PVD) coatings technology into bearing micropitting strategies (ESR 5).
Progress has been in the following key areas
- A new methodology for determining the kinetics of tribofilm growth using AFM has been developed and results are shown from this in Figure 1. New methodologies for the assessment of tribofilm formation and evolution using synchrotron radiation and Raman analysis. The apparatus is shown in Figure 2.
- A new rig for assessing hydrogen permeation in bearings has been developed using the devanthan cell (Figure 3). This enables the live assessment of the transport of hydrogen as a function of the tribological conditions. The results have shown that the lubricant additives have an important role to play and there are synergies with water (Figure 4).
- A new modelling framework was developed for assessing the boundary to mixed lubrication transition. The speed of calculation was improved dramatically by incorporating improvements in multi-grid methods, semi-system approach and progressive mesh densification. The results have been validated against previous EHL models (Figure 5) and have been used to validate experimental results (Figure 6)
- We have advanced the understanding of water effects in tribocorrosion/tribochemistry and have shown how the growth of the tribofilm is affected by the influence of water (Figure 7). We have then incorporated this into a semi-empirical model (Figure 8). This demonstrates the importance of tribofilm formation and removal.
- We have demonstrated that the addition of amine-based additives can dramatically reduce the level of micropitting (Figure 9) and have shown that this is due to localised surface chemistry associated with the crack tip (Figure 10).

Figure 1. In-situ generation of tribofilms (left – after 5 minutes) and (right – after 35 minutes)
Figure 2. Novel apparatus for the assessment of tribofilms in-situ using XANES and Raman spectroscopy

Figure 3. Tribo-Devanathan cell
Figure 4. Cumulative permeated hydrogen

Figure 5. Our modelling results which are in good agreement with EHL models
Figure 6. Simulated results from the model showing good alignment with experimental data

Figure 7. Tribofilm thickness and link to wear.
Figure 8. Model and experimental data for tribofilm growth

Figure 9. Micropitting with ZDDP (left) and reduction with diamine (right)
Figure 10. Schematic representation of the chemistry of the tribofilms in the absence of diamine (left) and with diamine present (right)