Tribological properties of sliding pairs with surface layer containing boron under mixed friction conditions

The aim of the present work is to determine the influence of surface layers containing boron on the friction parameters in sliding pairs under mixed friction conditions. The tribological evaluation included three production methods of surface layers with boron; pack boronizing, laser boronizing, and TiB2 coating deposited on 46Cr2 steel. Modified surface layers of ring specimens with 46Cr2 steel were matched under test conditions with a counterpart made from AlSn20 bearing alloy. Tested sliding pairs were lubricated with 5W/40 Lotos synthetic engine oil. The applied modification technologies of the surface layer of steel allowed for obtaining construction materials with predetermined tribological characteristics required for the elements of sliding pairs working undermixed friction conditions. The results showed differences in the wear of bearing alloy, as the effect of the interaction between the cooperating surface layers and of the physiochemical changes of their surfaces, induced by external forces. The TiB2 coating generated the highest friction resistance and bearing alloy wear. The pack borided surface layer reduces the friction coefficient, the moment during the start-up of the frictional pair and the wear of the bearing material. The analysis of the surface layer indicated that the content of aluminum on pack borided ring specimens reached 21%, and on the TiB2 coating, it exceeded 8%.