What is Boundary lubrication?

Answer 1

Boundary Lubrication (sometimes referred to as thin film lubrication) is a condition in which the lubricant film becomes too thin to provide total separation. This may be due to excessive loading, speeds or a change in the fluid's characteristics. In such a situation, contact between surface asperities (peaks and valleys) occurs. Friction reduction and wear protection is then provided through chemical compounds rather than properties of the lubricating fluid. Boundary lubrication often occurs during the start-up and shutdown of equipment or when loading becomes excessive. This condition can commonly be observed in certain types of gear sets that need to withstand sliding pressures and shock loading such as hypoid gear sets found in automotive differentials.

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