Effect of Pentaerythrite Tetraether-Based Lubricants on the Structure and Properties of Bronze in the BrA5—Steel 45 Friction Pair

Using X-ray structural, X-ray phase, and light metallographic microscopy, the mechanisms of the influence of lubricant compositions based on a dispersion medium — C₅–C₉ pentaerythritol ether (TEPE of the surface layers of BrA5 bronze after its friction with St45 steel were studied. Concentrated surfactants (surfactant-like agents) were used as dispersed phases (thickeners): lithium soap of 12-hydroxystearic acid (12-LioSt), calcium soap of 12-hydroxystearic acid (12-CaoSt), and complex calcium soap, which includes a composition of salts of 12-hydroxystearic and acetic acids (k-Ca). It has been shown that after friction of bronze, there is a variable change in the yield strength of the surface layer of the samples in all lubricant compositions (the Rebinder and Roscoe effects). The appearance of internal residual stresses in this layer as a result of tribo-deformation includes a mechanism of upward diffusion, which causes a concentration redistribution of components in the material, up to a complete cleaning of the subsurface layer from the atoms of the alloying element (selective transfer mode). It has been shown that the adaptive changes in the mechanical characteristics of the material (positive or negative) and its wear resistance depend on the colloidal-chemical indicators of the surface and oxidative activity of the lubricant composition (hydrophilic-lipophilic balance). Thus, adding 12-LioSt to the basic TEPE C₅–C₉ environment reduces the wear rate of bronze by 1.3 times, adding k-Ca reduces it by 6.5 times, and adding 12-CaoSt increases it by 10 %.

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