Tribological Characteristics of the Surface Layer of Steel Modified with Boron under Mixed Friction Conditions

The aim of the present work is to determine the influence of technologically produced boron surface layers on the friction parameters in the sliding pairs under mixed friction conditions. The current boronizing processes allow obtaining surface layers of high hardness and high resistance to corrosion and wear, with low brittleness and no tendencies towards cracking However, the operation characteristics of these layers depend on the chemical composition, the structure of the surface layer, the method and parameters of their production, as well as any possible thermal treatment. The tribological evaluation included ion nitriding, powder-pack boronizing, laser boronizing, hardening and tempering surface layers and TiB2 coating deposited on ring samples. The ring samples were made from 38CrAlMo5-10, 46Cr2 and 30MnB4 steel. Modified surface layers of ring samples were matched under test conditions with counter-sample made from AlSn20 bearing alloy. Tested sliding pairs were lubricated 15W/40 Lotos mineral engine oil. The tribological tests were conducted on a T-05 block on ring tester. The applied steel surface layer modification with boron allow creating surface layers with pre-determined tribological characteristics required for the elements of kinematic sliding pairs operating under mixed friction conditions. Boronizing reduces the friction coefficient during the start-up of the frictional pair and the maximum start-up resistance level is similar to the levels of pairs with ion nitride surface layers.