Tribotechnical Characteristics of the Iron-Based Composite at 500 °C

Abstract

The tribological characteristics of the Fe–W–CaF₂ composite antifriction material (CAM) in combination with 1Kh18N9T steel are examined in air at a temperature of 500 °С, a pressure of 0.8 to 3.3 MPa, and a sliding velocity of 0.5–2.0 m/sec. It is established that its friction coefficient, mass wear I_m, and linear wear I_l decrease, respectively, from 0.3 to 0.26, from 5 to 2 mg/km, and from 30 to <5 μm/km at constant pressure (0.8 MPa) with increase in the sliding velocity of the material from 0.5 to 2 m/sec. At a constant sliding velocity (0.5 m/sec) of the material, with increase in the pressure on the friction pair from 0.8 to 3.3 MPa, its friction coefficient f decreases from 0.3 to 0.26, whereas its mass wear Im and linear wear I_l increase, respectively, from 5 to 8.4 mg/km and from 30 to 57 μm/km. It is shown that secondary lubricating films form in friction on the working surface of the material. Like the initial material, they have a microheterogeneous structure and determine its antifriction properties. The solid solution of tungsten in α-iron with a bcc lattice hardened by inclusions of iron tungstate is a bearing structural component of the secondary lubricating films, and inclusions of iron oxides and calcium fluoride are antifriction structural components. The presence and content of the phases as well as the percentage of structural (antifriction and bearing) components in the secondary lubricating films depend on the friction conditions (Р · V) of the material. With increase in the amount of the bearing structural component in the secondary film, the wear of the material decreases. An increase in the content of the antifriction structural components in the film decreases the friction coefficient of the material.