# Evaluation of the Effectiveness of Surface Defect Removal by Slide Burnishing
## 2 Materials and Methods  
The study was performed on thin-walled samples made of C45 steel, with the following dimensions: outer diameter d = 56 mm, inner diameter d\({}_{0}\) = 50 mm, and width b = 10 mm. C45 is often used to make medium-duty machinery and plant components, e.g., discs or unhardened gears. Our previous study [23] confirmed the susceptibility of this steel grade to slide burnishing. The pre-treatment of thin-walled samples was grinding. It was carried out on a shaft grinder using a Norton Saint-Gobain electro corundum grinding wheel with the dimensions of 400 \(\times\) 50 mm and the characteristics of 8A60M7 VS3, using a grinding speed of \(\mathrm{v_{s}}\) = 35 m/s and a grinding depth of a\({}_{\mathrm{p}}\) = 0.01 mm. Surface defects (scratches) were made on the outer surface of the ring samples. To make the scratches, special \"scribers\" were used, the so-called surface defect generators, which were made from a sintered carbide rod. The working surfaces of the scribers were ground to obtain a conical surface. The double generating angle of cone formers was 90\({}^{\circ}\). The rounding radius of the cone was approximately 40 \(\mathrm{\SIUnitSymbolMicro m}\). Figure 1 shows the view of generators and the photograph of a scriber blade. Surface defects were generated using a Dematec DEM4000 machine (at Lublin University of Technology) by a digital multimeter. To ensure repeatability, a short-circuit detection option was used after the contact between the crack generator and the test sample. One end of the multimeter was connected to the defect generator, and the other to the ring sample. The generator was approached to the sample surface with a step of 10 \(\mathrm{\SIUnitSymbolMicro m}\). At each time a short-circuit was obtained, the \"scriber\" was pressed into the surface by a specified value. Five different nominal depths were used in the study: 10, 20, 30, 50, and 70 \(\mathrm{\SIUnitSymbolMicro m}\). The generator's feed rate was 300 mm/min. Figure 2 shows the stand for making surface defects. The next step was slide burnishing (SB) to reduce surface defects. The ring-shaped specimens were mounted on a mandrel that was fixed in the chuck of a C11/MB universal lathe (manufactured in Bulgaria). During slide burnishing, the mandrel performed a rotary movement at a speed of \(n\) = 160 rev/min. The tool consisted of a spherical cup-shaped tip with a radius of R = 2.0 mm and a spring mechanism (for exerting a pressing force F on the specimen). During burnishing, the tool performed a feed motion f. Figure 3 shows the slide burnishing stand, and Table 1 lists the technological parameters of the experiment. The slide burnishing conditions were selected based on our previous works [23; 24]. The visual evaluation of induced scratches and the effectiveness of their \"removal\" by slide burnishing was performed using a Keyence VHX5000 digital microscope (Keyence Ltd. HQ & Laboratories, Osaka, Japan). During the analyses, 500\(\times\) magnification and a technique of combining images were used. The Keyence VHX5000 microscope software allows us to create a 3D model (the assembly of a series of image functions) and then measure the depth in a section perpendicular to the surface of the test object. Figure 4 shows the model of a scratch and its depth. Figure 1: Photo of a surface defect generator, known as a scriber, and the geometry of a scriber blade. Figure 2: Stand for making surface defects. Figure 4: Example of a scratch defect and its depth. Figure 3: Stand for slide burnishing (SB). \begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Slide Burnishing Force F [N]** & **Feed f [mm/rev.]** \\ \hline
1 & 100 & 0.03 \\ \hline
2 & 100 & 0.08 \\ \hline
3 & 150 & 0.03 \\ \hline
4 & 150 & 0.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technological parameters of slide burnishing. The work also investigated surface topography and roughness, microhardness, and residual stresses.