The paper examines the effect of operating parameters of new high-speed nickel-based composite bearing materials alloyed by molybdenum and tungsten and with additions of a solid lubricant, calcium fluoride CaF 2 , on the formation of dissipative secondary structures (friction films). It is shown that friction parameters substantially influence the nature of secondary structures responsible for antifriction properties. The wear mechanism of the materials is studied in different conditions of friction. Antiscoring films with smoothed microgeometry of contact surfaces are formed at 800−1000 rpm under a load of 6 MPa in air. In these friction conditions, the films ensure high wear resistance of the nickel-based bearing materials for rotary offset printing machines.
This paper studies the effect of technological parameters to the manufacture of new effective antifriction composite materials based on 7HG2VМF tool steel grinding waste with CaF2 additions as solid lubricants in structures, having mechanical and tribological properties for high temperature friction (bearings perform at a temperature of up to 550°С, a sliding speed of 1 m/s, and a pressure up to 5.0 MPa, in air). This paper illustrates the mechanism of structure formation of the new materials and its effect on properties after using developed technological modes. Such technology can ensure a microheterogeneous fine-grained structure. The composite structure consists of a matrix based on tool steel waste and the uniformly distributed CaF2 solid lubricant. The metal matrix is pearlite and consists of an α-solid solution based on iron with hard grains of alloying elements of carbides. Such heterogeneous structure promotes a high level of antifriction properties under severe operating conditions. The behavior of CaF2 in the friction area under high temperature operating conditions has been shown. The CaF2 solid lubricant is evenly distributed over the entire friction surface. Calcium fluoride and chemical elements of the contact pair form an antifriction film, which provides self-lubricating conditions. The possibility of predicting and controlling the behavior of antifriction materials at a high temperature, by the selection of initial metal grinding waste, for ensuring the high level of functional properties, has been demonstrated. The use of grinding waste to produce effective antifriction materials makes it possible to partially solve the global problem of environmental protection.
The friction behavior of the formed antifriction films and their effect on the functional properties of the composite based on the powder nickel alloy EI929 with solid lubricant CaF2 at high temperatures was investigated. An antifriction film was formed on the contact surfaces during the friction process. Such a film was the result of the interaction of the contact surfaces with atmospheric oxygen at high temperatures. It contains oxides of alloying elements from materials of the frictional contact and solid lubricant calcium fluoride. The quantitative ratio of formed oxides depends on the temperature operating conditions of material. The data of thermodynamic simulation of the high-temperature interaction of the composite with oxygen coincide with the experimental data obtained by studying the fine structure of surface antifriction films. Antifriction films consist of oxide phases in combination with solid CaF2 lubricant. Anti-friction films provide high wear resistance of the self-lubricating composite in the range of temperatures 1073–1173 K due to the balance between the rate of their formation and wear. When the temperature exceeds 1200 K, the film loses its lubricating properties and acts as an abrasive substance due to the intense oxidation. Abrasive surfaces of materials were subjected also to microscopic examination, in which the mechanically mixed layer (MML) was described. The study of the friction surface roughness parameters confirmed the presence of the formed friction self-lubricating film and allowed to determine its parameters. The friction mechanism was the formation of an oxide layer combined with a solid lubricant, which provides high antifriction properties in the range of 1073–1273 K.
This article investigates the impact of manufacturing technology on the structure, mechanical, and tribological properties of new antifriction composite materials based on R6M5 high-speed tool steel grinding waste. The characteristics of the new composite’s structure formation and its impact on properties after use of the established technological modes, including grinding waste regeneration, were illustrated. It was demonstrated that such technology is capable of ensuring microheterogeneous structure. The material’s structure consists of the metal matrix based on R6M5 high-speed tool steel waste and uniformly distributed CaF2 solid lubricant in the steel matrix. As compared to known iron-based composites, this structure promotes a high degree of mechanical and tribological properties. During tribological tests, anti-seize thin films of 15–20 μm are formed on the contacting surfaces. These constantly renewable films contribute to the high antifriction properties of the composite under the studied friction conditions and provide a self-lubricating effect. Such films fully cover both the material’s surface and the counterface. The formation of antifriction films results in the self-lubrication mode. The findings of the study open up the possibility of predicting the friction behavior of a composite at high temperatures by selecting the initial metal grinding waste to ensure the appropriate level of properties. The extensive use of various alloy steel-based industrial grinding waste in the re-production cycle would significantly contribute to resolving the global environmental problem of protecting the environment from pollution.
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