*2.6. Study of Tribological Properties*

The friction scheme "shaft-block" was used in friction tests (Figure 2) [31,32].

**Figure 2.** Friction scheme. 1—sample; 2—counter body; 3—pendulum; 4—strain gauge. *M*—frictional moment; *N*—force acting on the counter body and the pendulum from the side of the sample; *F*—force acting on the pendulum from the strain gauge; *L*—distance from the axis of rotation to the axis of symmetry of the strain gauge, *R* – radius of the sample.

The counter body was made of tool alloy steel (wt.%: 0.9–1.2 Cr, 1.2–1.6 W, 0.8–1.1 Mn and 0.9–1.05 C) in the form of a plate with a semicircular notch 10 mm in diameter enclosing the surface of the sample. The sample was mounted on a shaft driven by an electric motor. The counter body was mounted on a platform sliding along cylindrical guides. The platform was moved using a pneumatic cylinder. The cylinder, guides and the platform were able to rotate with the pendulum. The pendulum shaft was located coaxially with the sample. Such a scheme makes it possible to preserve the common rotation axis for the sample and

the counter body as they exhaust and to avoid the influence of misalignment on the results of measurements of the frictional moment. Friction tests were carried out in dry friction mode under a load of 10 N. The sliding speed of the sample along the counter body was 1.555 m/s. The friction path was 1000 m. The parameters of the microgeometry of the friction tracks' surface were measured using the TR200 profilometer (Beijing TIME High Technology Ltd., Beijing, China). The temperature of the friction contact was measured on the friction track directly at the exit from the contact area using the MLX90614 digital infrared thermometer (Melexis Electronic Technology, Shanghai, China).
