Lubrication is critical for minimizing wear in mechanical systems that operate for extended time periods. Developing lubricants that can be used in engineering systems without replenishment — particularly those that are environmentally friendly — is very important for increasing the functional lifetime of mechanical components. In the present investigation, extended duration pin-on-disk experiments were carried out to determine the relative performance of a wide range of lubricant combinations in a commercial brake valve assembly. In the experiments, the lubricants were initially applied to the disk surface but were not replenished over a sliding distance of more than 6000 m. The experimental results revealed that the environmentally friendly lubricant boric acid was inefficient for reducing the wear in the surfaces tested. When combined with a commercial transmission fluid, however, the boric acid mixture proved highly effective in terms of both friction and wear performance. Based on the success of the combined lubricant experiments, the boric acid was then mixed with canola oil to form a completely natural lubricant combination. Based on further pin on disk experiments, this lubricant combination yielded the best wear performance of all the lubricants tested. The importance of these results, as related to the use of the natural lubricant combination in other engineering systems was subsequently ascertained and discussed.

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