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EN
The paper presents the results of research aimed at differentiation between the API GL performance levels of automotive gear oils. Tribological tests were conducted with the use of two different tribotesters. A four-ball apparatus and a crossed-cylinder wear tester were employed. Several dozen oils were tested, and various standardised measurements of their lubricating properties have been determined. Then, the measurements of the tribological properties were related to the particular API GL performance levels and the results obtained in the two tribotesters were compared. The most known measurements, which characterise the antiwear and extreme-pressure properties of lubricants, were determined with the use of the four-ball apparatus. Using the crossed-cylinder wear tester, the load-carrying capacity of the oil has been assessed through the Brugger test. The statistical analysis of the research results has shown the possibility of the differentiation between the API GL performance levels of automotive gear oils on the basis of the Brugger test. The Brugger test is characterised by relatively low time-consumption, and the crossed-cylinder wear tester is relatively inexpensive, thus this approach may give significant benefits to the laboratory testing automotive gear oils.
EN
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.
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