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

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°C, a pressure of 0.8 to 3.3 MPa, and a sliding velocity of 0.5–2.0 m/sec. It is established that the friction coefficient, mass wear I_m, and linear wear I_l of the composite 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 from 0.5 to 2 m/sec. At a constant sliding velocity (0.5 m/sec), with increase in pressure on the tribological system from 0.8 to 3.3 MPa, the friction coefficient f decreases from 0.3 to 0.26, whereas its mass wear I_m and linear wear I_l increase 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 starting material, they have a microheterogeneous structure and determine antifriction properties. The bcc solid solution of tungsten in α-iron 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 friction conditions (P · V). With increasing amount of the bearing structural component in the secondary film, wear of the material decreases. Higher content of the antifriction structural component in the film decreases the friction coefficient of the material.