## 3 Results and Discussion
### The Formation of a Sliding Layer on Steel under Dry Friction Conditions  
The tests were performed at loads of 10, 20, and 30 N, for speeds of 25 and 50 mm/s. An example of the test run for 10 N and speeds of 25 and 50 mm/s is shown in Figure 3. Tests for 20 and 30 N were performed in the same arrangement. Already during static contact, a change in the surface roughness of the samples was noticeable. This means that particles of expanded graphite had been transferred to the surface of the steel sample. This was noticeable for all loads. As the load increased, a slight decrease in roughness was visible. To illustrate the effect of the load on the operation of the friction node under dry conditions for 5 and 30-min cycles, at speeds of 25 and 50 mm/s, the results of the surface roughness of the samples are summarized in Figures 4 and 5. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Operating Conditions**} & \multicolumn{3}{c}{**Test Duration**} \\ \cline{2-4}  & **Rest [s]** & **Movement [min]** \\ \hline Dry counter-sample & & & \\ \hline Moist counter-sample & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Operating conditions of the friction node during testing. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{5}{c}{**Operating Conditions of the Friction Node**} \\ \hline \hline \multicolumn{5}{c}{Speed [mm/s]} \\ \hline \hline \multicolumn{5}{c}{25} & \multicolumn{3}{c}{50} \\ \hline \hline \multicolumn{5}{c}{Load [N]} \\ \hline \hline
10 & 20 & 30 & 10 & 20 & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values of load and speed parameters for the tested friction nodes. Figure 4: Change in the values of the Ra roughness parameters of steel samples working with dry graphite rings in a 5-min cycle under loads of 10, 20, and 30 N and speeds of 25 and 50 mm/s. Figure 5: Change in the values of the Ra roughness parameters of steel samples working with dry graphite rings in a 30-min cycle under loads of 10, 20, and 30 N and speeds of 25 and 50 mm/s. Figure 3: Changes in the values of Ra roughness parameters of steel specimens interacting with dry graphite counter-samples (speed 25 and 50 mm/s, load—10 N). After a 5-min cycle, an increase in surface roughness was noticeable compared to the initial value for all associations. The increase in load contributed to the decrease in roughness. Analyzing the effect of a 30-min friction node operation on surface roughness, it was noticeable that the roughness of the sample decreased compared to the initial value. A greater decrease in roughness was noted for a speed of 50 mm/s. The Formation of a Sliding Layer on Steel under the Conditions of Interaction with Moist Expanded Graphite  
The course of tests for 10 N and speeds of 25 and 50 mm/s during the interaction of steel samples with moist rings is shown in Figure 6. Tests for 20 and 30 N were performed in the same arrangement. During static contact between steel samples and moist graphite rings, a change in surface roughness was observed after 30 s of friction node loading. For the initial surface roughness values, an increase in roughness was noted with a 10 N load. With increasing load, a decrease in the surface roughness of the sample was noted. The effect of load on the surface roughness results of samples mated with moist rings for 5 and 30-min cycles, at speeds of 25 and 30 mm/s is shown in Figures 7 and 8. Figure 6: Changes in the value of the Ra roughness parameter of steel samples mating with moist graphite rings (speed 25 and 50 mm/s, load 10 N). Figure 7: Change in the values of the Ra roughness parameters of steel samples working with moist graphite rings for 5 min under loads of 10, 20, and 30 N and speeds of 25 and 50 mm/s. During the 5-min friction node operation at a speed of 25 mm/s, there was a decrease in surface roughness as the load increased. Increasing the speed to 50 mm/s contributed to a faster and greater decrease in surface roughness.