text: Paper presents the research results of changes taking place in the surface layer during friction process in presence of lubricant with different chemical composition.
  The tested greases consisted of base oil (synthetic and semisynthetic), thickener (organic and inorganic) and lubricating additive were investigated using four-ball machine.
  To explain the action of grease under test conditions, the author performed wear scar surface analyses using scanning electron microscopy and energy dispersive spectrometry (SEM/EDS) (to elements on the surface and their distribution) and IR microspectro-photometry (to identify a kind of chemical groups of organic compounds).