Influence of Testing Parameters on the Surface Quality of Steel Roller-Roller System Under Grease Lubrication

This paper presents the influence of commanding parameters as load and relative sliding speed, on the surface characteristics. Tests were done on a roller-roller tribotester. There were studied the influence of load, relative sliding speed and lubricant on the skewness and the kurtosis of the surface profile, but also on common parameters such as Ra and Rz. Such a study may be used for selecting a suitable lubricant (especially grease), after testing it under severe conditions, close to the actual ones. Profilograms indicate that treated steel has a better tribological behavior, under the above-mentioned testing conditions, for a roller-roller system. When running at low temperatures, there were noticed gripping traces, pointed out in shape and size by profilograms recorded on the roller generatrix. For all testing conditions, the more viscous grease (UM185Li2 EP – multifunctional grease) had a better behavior as concerning the profile parameters of the roller surfaces, and it provides a probably almost continuous film between rollers thus, a good protection of the metallic surfaces, process also underlined by low values for the recorded friction moment. A comparative study of the surface topography, obtained under the same testing conditions, may do at least a qualitative hierarchy of the grease grades, which could give recommendations for selecting lubricants and durability improvement of actual tribosystems.