## 3 Results
### Surface Morphology  
The surface morphology of nitrided samples reflects the competition between the processes of high-temperature oxidation and anodic dissolution. It was found that the weight of the samples decreases under all processing modes, which indicates the prevalence of dissolution over oxidation (Table 2). The results of roughness measurements (Table 2) and analysis of the surface morphology (Figure 9) showed that PEP leads to the formation of a more uniform surface and a decrease in roughness compared to an untreated and nitrided surface. The greatest reduction in roughness occurs after PEP in a sulfate electrolyte (3.1 times compared to an untreated surface and 2.6 times with a nitrided surface after 2 min of PEP), while polishing in a chloride-glycerol electrolyte reduces material removal. Increasing the PEP time leads to a decrease in roughness.  
Figure 8: Microhardness distribution in the surface layer of CrWMn steel after various types of treatment. ChG—the solutions of ammonium chloride and glycerol, S—the solutions of ammonium sulfate.  
Figure 7: Microstructure of the cross-section of the CrWMn steel surface after PEN: 1—outer layer with inclusions of iron nitrides and residual austenite, 2—martensitic structure with inclusions of iron carbides.  
Figure 9: Morphology of the Cr\(\
u\)WMn steel surface after various types of treatment: (**a**) Untreated; (**b**) PEN; (**c**) PEN and PEP in a solution of NH\({}_{4}\)Cl and C\({}_{3}\)H\({}_{8}\)O\({}_{3}\) for 1 min; (**d**) PEN and PEP in a solution of NH\({}_{4}\)Cl and C\({}_{3}\)H\({}_{8}\)O\({}_{3}\) for 2 min; (**e**) PEN and PEP in (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\) solution for 1 min; (**f**) PEN and PEP in (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\) solution for 2 min.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Electrolyte** & **PEP Time** & **(min)** & **A\(m\) 1 (mg)** & **R\({}_{a}\) 2 (\(\mu\)m)** & **R\({}_{a}\) 3 (\(\mu\)m)** & **M 4** & **T\({}_{P}\) 5 (C)** & **A\(m_{p}\) 6 (mg)** & **_htr_ 7 & **\(\Delta\) 8** \\ \hline Untreated & & & 1.00 \(\pm\) 0.10 & 6.72 \(\pm\) 0.28 & 0.579 & 53 & 15.4 & 0.082 \(\pm\) 0.002 & 0.52 \(\pm\) 0.01 \\ PEN & & 73.2 & 0.85 \(\pm\) 0.07 & 5.92 \(\pm\) 0.45 & 0.292 & 96 & 1.1 & 0.062 \(\pm\) 0.001 & 0.23 \(\pm\) 0.01 \\ NH\({}_{4}\)Cl + & 1 & 38.2 & 0.58 \(\pm\) 0.04 & 3.78 \(\pm\) 0.40 & 0.245 & 67 & 0.7 & 0.061 \(\pm\) 0.001 & 0.21 \(\pm\) 0.01 \\ C\({}_{3}\)H\({}_{8}\)O\({}_{3}\) & 2 & 79.6 & 0.47 \(\pm\) 0.02 & 2.81 \(\pm\) 0.05 & 0.294 & 70 & 1.9 & 0.058 \(\pm\) 0.001 & 0.23 \(\pm\) 0.01 \\  & 1 & 57.8 & 0.40 \(\pm\) 0.03 & 2.37 \(\pm\) 0.11 & 0.218 & 69 & 0.5 & 0.060 \(\pm\) 0.001 & 0.20 \(\pm\) 0.01 \\ (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\) & 2 & 100.7 & 0.32 \(\pm\) 0.03 & 1.90 \(\pm\) 0.23 & 0.264 & 67 & 1.6 & 0.056 \(\pm\) 0.001 & 0.22 \(\pm\) 0.01 \\ \hline \end{tabular}  
* the loss of sample weight during treatment; 2; 3 the surface roughness; 4 the friction coefficient; 5 the temperature in the friction contact zone; 6 the weight wear, 7 the relative introduction of surface roughness; 8 the Kragelsky–Kombalov criterion.  
\end{table}
Table 2: Experimental and calculated characteristics of samples before and after PEN and PEP.  
The reduction in roughness after polishing in a sulfate electrolyte is additionally associated with the filling of depressions with oxides formed during surface passivation (Equations (3) and (4)). During passivation, the depressions of micro-irregularities will be filled with oxides, and with the simultaneous occurrence of electrochemical dissolution and passivation processes, predominantly micro-protrusions will be removed.