Abstract
Diamond-Like Carbon (DLC) coatings can reduce fluid friction in TEHL contacts (thermo-elastohydrodynamic lubrication) of meshing gears. This study investigates the influence of different base oils i.e., mineral, polyalphaolefin and polyglycol oil on the friction of DLC coated spur gears. Thereby, a transient TEHL simulation model based on the finite element based full-system approach coupled iteratively with the thermal equations is applied, considering mechanical and thermal properties of the DLC coatings. Results show a clear reduction of fluid friction in DLC coated gears for all considered lubricants. This can be traced back to higher TEHL temperatures for DLC coated gears, which is due to its low thermal inertia resulting in a thermal insulation effect.
Highlights
The increasing performance and efficiency requirements of drive systems are stimulating the further development of geared transmissions
Whereas the no-load power loss is mainly caused by the circulation of lubricant [1], the load-dependent power loss of gears is determined by sliding velocity, normal force and the coefficient of friction along the path of contact [2,3]
Recent experimental and theoretical investigations have shown that Diamond-Like Carbon (DLC) coatings can quite significantly reduce friction in TEHL contacts
Summary
The increasing performance and efficiency requirements of drive systems are stimulating the further development of geared transmissions. Their power losses can be divided into no-load and load-dependent power losses. Whereas the no-load power loss is mainly caused by the circulation of lubricant [1], the load-dependent power loss of gears is determined by sliding velocity, normal force and the coefficient of friction along the path of contact [2,3]. Recent experimental and theoretical investigations have shown that Diamond-Like Carbon (DLC) coatings can quite significantly reduce friction in TEHL contacts (thermo-elastohydrodynamic lubrication). Proposed explanation of the friction reduction by DLC coatings in fluid lubrication regime are wall slip related to the wetting behavior and thermal insulation effects related to the coatings’ thermal properties
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