Substitution of Inexpensive Bench Tests for the FZG Scuffing Test—Part I: Calculations

Abstract

The standardized FZG apparatus is widely applied for assessing the anti-scuffing properties of gear lubricants. However, this test is very time-consuming and expensive. For the development of new transmission lubricants, quicker and less expensive tests would be useful. In this two-part article, the possibility to qualify gear lubricants by means of two common bench tests (SRV Optimol and four-ball) was investigated. In the first part, the different test rigs (FZG, SRV, four-ball) are presented and the parameters related to scuffing according to literature (lubricant film thickness, flash temperature and contact pressure) are calculated for the three testers. In the second part, test results of eight lubricants obtained with the three test rigs are presented and compared. Results showed a.o. that the SRV wear scar diameter and the four-ball load-wear index correlated with the FZG failure load stage. Inconsistencies between test results are clarified based on lubricant composition and the parameters related to scuffing calculated in the first part. The relevance of the different scuffing criteria is discussed. Finally, quicker and less expensive, but reliable test procedures than FZG are presented to determine the resistance to scuffing of gear lubricants.

KEY WORDS:

• Gear Lubricants
• Scuffing
• Bench Tests
• Wear