An experimental and analytical study of the effect of water and its tribochemistry on the tribocorrosive wear of boundary lubricated systems with ZDDP-containing oil

• Water delays the growth of the tribofilm in the running-in period and affects tribocorrosive wear.
• The higher the water concentration the lower the tribofilm growth rate.
• A link was made between wear and the tribofilm behaviour.
• The whole growth behaviour of the tribofilm can be significantly important to characterize wear.
• Experimental results were used in the numerical model to adapt the tribochemistry model to the tribocorrosion conditions.

Water has long been recognised as a contaminant in lubricants. It can affect wear performance, especially in bearing systems, in complex ways. Water can also induce corrosion, which in turn can enhance wear. The individual parts of any tribocorrosion system are related to a complex mix of system parameters such as lubricant and additives, relative humidity and temperature. The effect of different water concentrations and different temperatures has been studied experimentally in this work. A modification to Archard׳s wear coefficient was applied with respect to the experimental measurements. The new wear model considering the effect of water was implemented into the previously-reported numerical model to develop a new semi-deterministic numerical wear model adapted to the tribo-corrosion system in this work.