Investigations on the Influence of Synthetic Lubricants on the Pitting Load Carrying Capacity of Cylindrical Gears

Synthetic lubricants show advantageous properties compared to mineral oils. In gearboxes, a higher pitting load carrying capacity can be achieved, enhancing the power density. ISO 6336-2 is a well-known standard for calculating the safety factor against pitting for gears. The standard was mainly developed based on test results with mineral oils, giving limited assessment on the pitting load carrying capacity for synthetic lubricants. In this research, pitting load carrying capacity tests were conducted on an FZG back-to-back gear test rig with different lubricants based on mineral oil, polyalphaolefin and polyglycol, each of ISO VG 100. The results were analyzed with the standard ISO 6336-2 and an alternative approach according to Knauer (FZG, 1988), which addresses lubricating properties more in-depth. The analysis of the test results shows the limitations of the standard and further need for research to adequately quantify the pitting load carrying capacity of synthetic lubricants.