INFLUENCE OF FRICTION REGIMES ON THE TRIBOTECHNICAL PROPERTIES OF COMPOSITES BASED ON PTFE AND CARBON FIBERS

Abstract

The paper presents the results of tribotechnical tests of polymer composite materials based on polytetrafluoroethylene (PTFE) and carbon fibrous activated material UVIS-AK-P (SPC UVIKOM LLC) depending on the contact pressure in dry and boundary friction modes in various oils. I-20A industrial oil, Siboil TAD-17u transmission oil, and Rosneft Gidrotec HLP 46 hydraulic oil were used as liquid lubricants for the friction of polymeric materials. For tribotesting, a polymer composite with a content of 5 % wt. UVIS-AK-P, obtained using sequential mixing of filler with PTFE and the technology of joint activation of components in a planetary mill, is the most wear-resistant material according to the results of previous studies. It has been established that despite the heavy wear at increased bearing pressure during dry friction, unfilled PTFE does not undergo plastic deformation and maintains a low coefficient of friction practically unchanged. It has been found that the friction coefficient passes through a minimum during dry friction of a composite with CF at a load of 350 N. It is associated with the transition of the elastic contact of the interacting elements of the surfaces of the metal-polymer tribosystem to the plastic one with increasing load. During friction of PTFE in a lubricating oil environment, a significant decrease in mass wear, friction coefficient and temperature in the contact zone are observed due to the formation of secondary structures on the friction surfaces and the significant flexibility of PTFE. This increases the actual area of the tribocontact, which reduces the value of real normal contact stresses. During friction of polymer composite materials in the environment of lubricating oils, a decrease in the friction coefficient and the area of the friction track by 1.7-2.7 times was recorded as well. Deformations, groove formation and mass wear were not observed. It has been revealed that the greatest effect of increasing the wear resistance and permissible friction load and lowering the temperature in the friction zone of PTFE and composite is observed when using Siboil TAD-17u transmission oil. This is due to the presence of special antifriction additives in this oil brand and a decrease in the actual contact of the working surface of the polymer material with the lubricant, which helps to reduce the intensity of the destructive process in the surface layer while contacting with the lubricant.