A new scuffing shock test method for the determination of the resistance to scuffing of coated gears

An improvement in the scuffing resistance of toothed gears is achievable by e.g. the deposition of thin, hard coatings onto the gear teeth. However, the testing of the scuffing resistance of coated gears requires the application of specialised test methods. This paper presents a new test method, designed by the authors, called “gear scuffing shock test for coatings”. This method is based on the test method denoted as FZG S-A10/16,6R/110 developed at the Technical University of Munich. Because the FZG test method is dedicated exclusively to lubricating oils, its application for testing coated gears required introducing significant modifications. The developed method has been verified during the testing of the scuffing resistance of gears coated with the low-friction a-C:H:W coating and composite low-friction MoS2/Ti coating. Various material combinations were tested: coating–coating (both gears coated), coating-steel, steel-coating, and for reference steel–steel (both gears uncoated). Mineral, automotive gear oil of API GL-5 performance level, and SAE 80W-90-viscosity grade was used for lubrication. It has been shown that this test method can be successfully applicable to test the scuffing resistance of coated gears—it has a resolution good enough to differentiate between the tested material combinations.