## 3 Results
### Study of Wear Mechanism  
The process of contacting parts depends on geometric parameters, roughness, waviness, deviations from the correct shape, and physical and mechanical properties of surfaces, which can be controlled during the processing of parts. To increase wear resistance, it is advisable to create sliding surfaces with a suitable roughness. The protrusions that form during friction and surface treatment have different shapes and height distributions. Therefore, when modeling surface topography, it is important to take into account the type of technological processing and include experimentally obtained parameters in the statistical distribution laws that describe real surfaces.  
Figure 11: Morphology of friction tracks on the CrWMn steel surface after various types of treatment: (**a**) Untreated; (**b**) PEN; (**c**) PEN and PEP in a solution of NH4 Cl and C3H8O3 for 1 min; (**d**) PEN and PEP in a solution of NH4 Cl and C3H6O3 for 2 min; (**e**) PEN and PEP in (NH4)2 SO4 solution for 1 min; (**f**) PEN and PEP in (NH4)2 SO4 solution for 2 min.  
The Kragelsky-Kambolov criterion was used as the main characteristic for assessing the operational properties of the surface:  
\[\Delta=\frac{R_{max}}{rb^{1/\
u}}, \tag{5}\]  
where \(R_{max}\) is the maximum height of irregularities; \(\
u\) and \(b\) are the parameters of the distribution of roughness of a rough surface along the height, determined from experimental data [43].  
This indicator allows for a more complete assessment of surface roughness. In addition to the accepted experimental indicators of profilograms, it includes statistical data on the distribution of irregularities as well as their rounding radius.  
Bodies of double curvature modeled the shape of the protrusions of micro-irregularities in the profile:  
\[\tau=\frac{9R_{a}^{2}S_{m}^{2}}{128\big{(}5.5R_{a}-R_{p}\big{)}^{3}}, \tag{6}\]  
where \(R_{a}\) is the average deviation of the surface profile from the mean line; \(R_{p}\) is the value of the highest protrusion from the midline; and \(S_{m}\) is the average pitch of irregularities.  
The nature of the violation of the frictional connection and the complex processes occurring in surface layers and microvolumes significantly depend on a number of factors: geometric, mechanical, physical, and chemical. One of the most powerful factors is geometric, characterized by the ratio of the penetration depth or compression value \(h\) to the radius of a single asperity \(r\) (6), calculated according to the method [43]. This characteristic allows us to distinguish between elastic contact, plastic, and microcutting:  
\[\frac{h}{r}=R_{p}\bigg{(}\frac{N}{\eta p_{r}A_{c}}\bigg{)}^{\frac{1}{r}}. \frac{128\big{(}5.5R_{a}-R_{p}\big{)}^{3}}{9R_{a}^{2}5_{m}^{2}} \tag{7}\]  
It has been shown that as a result of PEN, as well as subsequent PEP, the value of the Kragelsky-Kambalov criterion decreases (Table 2). Calculation of the value of relative penetrations (7) shows that in all cases of processing, frictional bonds are broken due to plastic displacement (since \(h/r<0.1\) for plastic deformations, \(h/r<0.01\) for elastic deformations, and \(h/r>0.1\) during microcutting) of the material during plastic flow around the deforming protrusion. The wear mechanism of all modified samples is fatigue wear due to dry friction and plastic contact.  
The \(\Delta\) criterion determines the load-bearing capacity of the surface profile during frictional interaction. As its value decreases, the load-bearing capacity of the profile increases. If the surface wear occurs without molecular interaction of the rubbing bodies, as it happens with the untreated sample and samples after PEN and PEP, then the surface microgeometry will determine the wear resistance of the surface. In the case under consideration, there is a correlation between the Kragelsky-Kobmalov value with the friction coefficient and weight wear (Table 2).