## 3 Results
At a drop angle of about 20-35\({}^{\circ}\), the effect of the abrasive on the surface is shown in Figure 17b. The composition of the steel surface of used blades, determined by EDS, is shown in Figure 8:4 This composition corresponded approximately to the composition of the blades determined by spectral analysis (Table 3): 91.7-92.6% iron, 3.29-3.86% oxygen, and other elements on the surface of used blades. The increased oxygen content on the surface of the blades was a natural consequence of the oxidation process at temperatures higher than ambient. Unlike EDS, the spectral analysis method used to detect the chemical composition of blade steel did not detect oxygen (Table 1). Other elements found on the surface of the blades (higher carbon content than steel, aluminum, calcium, potassium, and sodium) were due to the interaction with the chaff mass and contamination of the straw mass with abrasives. Silicon, manganese, chromium, and carbon are constituents of steel (Table 1). A solid coating of resinous plant debris formed on the surface of the blade (Figure 18a), which cracked as it dried, and the pores showed the release of gases during the formation of this coating. The main constituents of the resincontaminated surface of the Alt. 2 blades (EDS analysis) are listed in Table 3, and the spectrum of chemical composition is shown in Figure 18b. Silicon and aluminum are abrasive particles that remained in the resin. Iron, carbon, and steel alloy elements (silicon, manganese, and chromium) were components of the steel analyzed through the resin film. The high amounts of oxygen and carbon in the resin film were plant residues. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Hardness, HV** & \
\begin{tabular}{c} **Blade Angle \(\Theta\),** \\ **Degree** \\ \end{tabular} &
\begin{tabular}{c} **Wear I, g** \\ **I = f (HV, \(\Theta\))** \\ \end{tabular} \\ \hline Original & 515 \(\pm\) 14 & 24.6 & 3.71 & 3.7086 \\ Alt. 1 & 394 \(\pm\) 12 & 24.0 & 4.18 & 4.1790 \\ Alt. 2 & 568 \(\pm\) 11 & 20.9 & 3.28 & 3.2789 \\ Alt. 3 & 469 \(\pm\) 11 & 27.1 & 3.88 & 3.878 \\ Alt. 4 & 540 \(\pm\) 12 & 25.4 & 3.54 & 3.5385 \\ Alt. 5 & 349 \(\pm\) 9 & 29.2 & 4.77 & 4.7685 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The hardness of the blades, the initial angle, and the wear of the blade. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Sample** & **Fe** & **C** & **O** & **Si** & **Cr** & **Al** & **K** & **Ca** & **Mg** & **Cl** & **Na** & **Mn** \\ \hline Resincontaminated & 39.4– & 16.64– & 25.6– & 0.41– & 0.59– & 0.7– & 0.97– & 0.52– & 0.32 & 0.68 & 0.52– & 0.88 \\ surface (Alt. 2) & 52.8 & 22.9– & 31.1 & 1.53 & 0.94 & 1.41– & 1.15– & 0.73– & 0.35– & 0.2 & 0.25 & \\ Clean surface & 91.7– & 0.85 & 3.29– & 0.24– & 1.45– & 0.13 & 0.37– & 0.35– & 0.2 & 0.25 & \\ (Alt. 5) & 92.6 & 3.86 & 0.32 & 1.7 & 0.47 & 0.5 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical compositions of the resincontaminated surface of blade Alt. 2 and the clean surface of blade Alt. 5 (EDS analysis). The SEM image of the \"clean\" surface (Alt. 5), on which no scales were formed due to the low angle of falling of the chopped mass, and the spectrum of the chemical composition of this surface are shown in Figure 18c,d. The surfaces of the blades with the lowest hardness were subject to the greatest mechanical damage and wear (Figure 19). The initial surface roughness of the blades (main cutting planes) was quite different and ranged from 0.226 to 0.589 \(\upmu\)m (Figure 20). It can be assumed that it was influenced by blade manufacturing technology--the method and modes of machining technology. Due to the chopping work, the roughness of the blade surfaces may increase or decrease during the wear process, and it may be related to the blade's hardness. The results showed a general trend in which the lower the hardness of the blades, the greater the changes in roughness that occurred during use.