# Evaluation of the Effectiveness of Surface Defect Removal by Slide Burnishing
## 3 Results and Discussion  
### Visual Defects Analysis Before and After Slide Burnishing  
In the first step of the analysis, photographs of the defects before and after slide burnishing are presented in tables, followed by their quantitative description. Table 2 shows an example of a comparison of the scratches before and after burnishing conducted with a force F = 100 N and a feed f = 0.08 mm/rev. Before burnishing, one can observe characteristic defects resulting in the shape of the scratch generator moving along the axis of the workpiece. The tool left a symmetrical groove with characteristic material flashes above the base surface (as shown in Figure 4). The burnishing process removed the scratch, especially for smaller initial depths. Up to a nominal depth of 20 \(\upmu\)m, the scratches were completely removed, whereas for a nominal depth \(\geq\)30 \(\upmu\)m, the traces of surface defects are still visible. For all cases, the flashes above the base surface were removed as a result of the action of the burnishing tool on the machined surface.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Nominal** & **Before Slide Burnishing** & **After Slide Burnishing** \\ \hline
**Depth (\(\upmu\)m)** & **Before Slide Burnishing** & **After Slide Burnishing** \\ \hline
**20** & **10** & **10** \\ \hline \hline \end{tabular}
\end{table}
Table 2: Example of a comparison of the scratches before and after slide burnishing, for F = 100 N and f = 0.08 mm/rev. (magnification \(\times\)500).  
Table 3 presents an example of a comparison of the surface defects after burnishing as a function of the parameters used for slide burnishing a scratch with the largest nominal depth of 70 \(\upmu\)m. The use of a smaller feed results in smaller contact distances and a longer contact time, which increases the intensity of plastic deformation and, thus, the effectiveness of removing surface defects. Similarly, as the force is increased, the effectiveness of removing surface defects increases.  
Figures 5 and 6 show the depths of surface defects obtained during the experiment. At the burnishing forces of F = 100 N and F = 150 N, the surface defects with a nominal depth of 10 and 20 \(\upmu\)m were removed. For the depth of 30 \(\upmu\)m and above, there was a significant reduction in the depth of surface defects. The maximum degree of defect depth reduction is 97% and was obtained for a defect with a nominal depth of 30 \(\upmu\)m and burnished with F = 150 N and f = 0.03 mm/rev. Reducing the feed and increasing the force leads to a reduction in the depth of the surface defects. The depth of the surface defects after slide burnishing is 2 to 27 times smaller than the nominal value. For the entire range of burnishing technological parameters applied in the experiment, the flashes protruding above the base surface of the ring-shaped samples were removed. The factors affecting the effectiveness of surface defect removal are pressure force and burnishing feed. Taking the economic aspect into account, an increase in feed leads to reduced machining time as  
\begin{table}
\begin{tabular}{c c c} \hline
**Nominal** & **Before Slide Burnishing** & **After Slide Burnishing** \\ \hline
30 & & \\
50 & & \\
70 & & \\ \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 5: Depth of scratches after slide burnishing (**a**) and scratch depth reduction rate (SDRR) (**b**) with a force of F = 100 N as a function of the nominal depth.  
Figure 6: Depth of scratches after slide burnishing (**a**) and scratch depth reduction rate (SDRR) (**b**) with a force of F = 150 N as a function of the nominal depth.