Abstract
Base oil type, oil viscosity, additive type and content have a strong influence on typical gear failures. As it is not possible to quantify the lubricant influence on load carrying capacity simply from the knowledge of physical or chemical oil data many test methods were developed for the evaluation of mechanical-technological lubricant properties. Simple low-cost bench test methods often show poor correlation with practice. From experience and systematic investigations it can be shown that testing of gear lubricants can adequately be performed only in gear test rigs using specified test gear geometry. In continuous work over many years the standard FZG back-to-back gear test rig was developed and improved for different types of gear failure simulation. The standard FZG oil test A/8, 3/90 is widely used for the evaluation of the scuffing properties of industrial gear oils. Automotive gear oils of GL4 level can be tested in the step test A10/16.6R/90, axle oils of GL5 level in the shock test S-A10/16.6R/90. For the slow speed regime the wear test C/0.05/90 : 120/12 can be applied. The influence of lubricants on the micropitting performance of gears can be evaluated in the micropitting test GF-C/8, 3/90. Different pitting tests are available as single stage tests PT-C/9 : 10/90 or load spectrum tests PT-C/LLS : HLS/90. A universal test PITS Ci85 TS combining pitting and oil ageing performance was developed. The results of such tests can be introduced as "strength values" for the lubricant into load carrying capacity rating methods.
