OBRABOTKAMETALLOV Vol. 27 No. 1 2025 technology and cooling. However, increasing the lubricating effect often leads to a deterioration of the cooling effect of such MWFs. This circumstance necessitates the search for alternative solutions that result in MWFs possessing both high lubricating and cooling properties. Based on the above considerations, it became necessary to conduct experimental studies aimed at developing modified oil-based MWFs using NMAs as the primary modifying element. The objective is to reduce energy consumption in the cutting process, improve the quality of the machined part, and extend tool life. The use of NMAs offers several advantages. For instance, they are naturally occurring minerals found in abundant quantities within the Earth’s interior and are relatively inexpensive. One type of nanoclay mineral is bentonite, which is primarily composed of montmorillonite (a nanodispersed silicate with a sheet-like structure). From a physicochemical perspective, NMAs exhibit positive characteristics: they can undergo hydrocracking of their structural packet layers during hydrogenation, providing hydro-lubrication between the layers. This contributes to an increase in the tribological efficiency of the MWFs. This phenomenon distinguishes the tribological properties of montmorillonite from those of the friction modifiers described earlier. During hydrogenation of this additive, compared to the aforementioned frictionmodifiers, the unclinching action of surface-sorbed water causes the friction between mineral packets to transition from dry to liquid or boundary lubrication. When hydrated mineral particles enter the contact zone between the tool and the workpiece, carried by the oil-based MWF, they function as “nanoscale sliding bearings” [16, 17], allowing the tool and workpiece to be in contact, which reduces the probability of adhesive wear of the tool. The temperature generated in the contact zone of the tool and the workpiece acts on the surface watersorbed NMA packets contained in the oil-based MWF, resulting in moisture evaporation and providing an endothermic effect. A unique characteristic of nanoclay minerals is that the released vapor remains in the system during the evaporation process. When the temperature decreases, the vapor condenses, returning to the mineral structure. Improving the tribological characteristics of MWFs is particularly important in the process of cutting hard-to-machine materials, including stainless steels, because access of the MWF to the contact zone is often limited when processing these materials. Consider the case where a standard MWF, without additives to prevent adhesive setting, is used when machining hard-to-machine materials. Due to the high specific loads present in the cutting process acting on the tool contact surfaces, displacement of the MWF and subsequent adhesion of the chip to the tool base occurs. Thus, conditions for adhesive bonding between the front face of the cutting tool and the chip are created (Fig. 1, a). In the second case, using an oil-based MWF with graphite or molybdenum disulfide additive in the cutting process (Fig. 1, b), the additive enters the contact zone and counteracts the adhesion of chips to the cutting tool, thereby improving friction conditions in the cutting zone. This is achieved by preventing adhesive bonding of graphite or molybdenum disulfide layer packets with each other. Given the similarity of crystal lattices between graphite or molybdenum disulfide and nanoclay minerals, shear between layers is possible. In the case of graphite or molybdenum disulfide, this shear occurs “dry”, while in the case of nanoclay minerals, liquid friction conditions are created, accompanied by hydrocracking (Fig. 1, c), which directly influences the tribological properties of the MWFs. To evaluate the thermodynamic transformations of NMA that can occur in oil-based MWFs during machining by cutting, we will analyze their behavior during hydration and dehydration. This additive possesses a crystal lattice consisting of three layers, forming negatively charged packets that create repulsive forces, providing a wedging effect [5]. The aforementioned nanoclay minerals’ inherent thermodynamic properties enable their use as additives to oil-based MWFs. In reference [18], a detailed thermal analysis of montmorillonite is presented, highlighting the temperature range (80–220 °C), in which the endothermic (heat-absorbing) effect is manifested. At the
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