Effect of Pentaerythritol Tetraether-Based Lubricants on the Structure and Properties of Bronze in the CuAl5–Steel C45 Friction Pair

Methods of X-ray diffraction, X-ray phase analysis, and optical metallographic microscopy were used to study the mechanisms of influence of lubricating compositions based on a dispersion medium, tetraether pentaerythritol C5–C9 (TEPE C5–C9), with soap dispersed phases on the structure and physicomechanical characteristics of the surface layers of CuAl5 bronze after its friction in a pair with C45 steel. Concentrated surface-active substances (surfactants) were used as dispersed phases (thickeners): lithium soap of 12-hydroxystearic acid (12-LioSt), calcium soap of 12-hydroxystearic acid (12-CaoSt), as well as complex calcium soap, including a composition of salts of 12-hydroxystearic and acetic acids (k-Ca). It has been shown that after friction of bronze, an alternative change in the yield strength of the surface layer of the samples (Rehbinder and Roscoe effects) occurs in all lubricating compositions, depending on the composition. The appearance of internal residual mesostresses in this layer as a result of tribodeformation triggers an ascending diffusion mechanism, causing a concentration redistribution of the components in the material, up to the complete removal of the alloying element atoms from its near-surface layer (selective transfer mode). It is shown that changes in the mechanical properties of the material and its wear resistance depend on the colloidal-chemical parameters of the surface and oxidative activity of the lubricant composition, determined by the hydrophilic-lipophilic balance of the molecules of its components. Thus, the introduction of 12-LioSt additive into the base medium of TEPE C5–C9 reduces the wear rate of bronze by 1.3 times, the addition of k-Ca additive, by 6.5 times, and the introduction of 12-CaoSt additive increases this rate by 10%.