# The Influence of Grain Size on the Abrasive Wear Resistance of Hardox 500 Steel
## 3 Results and Discussion
### Abrasive Wear Resistance
[PERSON] [15] also analyzed commercial 500 HBW wear-resistant steel, concluding that surface deformation hardness, rather than initial hardness, better correlated with abrasive wear resistance. However, it is worth noting that the described tribological test involved impact-abrasive phenomena, which could not be replicated in T-07 tests. Only a narrow, deformed subsurface zone, similar across all heat treatments, was observed and will be described below. Furthermore, [PERSON] et al. [45] observed that the transition from a highly deformed layer to the core material should be smooth to minimize the risk of local stresses that could lead to premature failure or cracking during operation. Results aligned with findings on grain size's effect on tribological behavior, showing that reducing austenite grain size improves wear resistance in martensitic steels of comparable hardness [15]. [PERSON] et al. [15] noted critical phenomena regarding initial hardness, with the lowest mass loss recorded in steel austenitized at 860 \({}^{\circ}\)C, which also had the highest initial hardness among the studied variants. This outcome parallels the \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**State of Heat Treatment** & **[1] M = 468.01** & **[2] M = 529.42** & **[3] M = 534.26** & **[4] M = 521.83** & **[5] M = 513.30** & **[6] M = 507.42** \\ \hline DS [1] & & 0.000138 & 0.000138 & 0.000138 & 0.000138 & 0.000138 \\ \hline T\({}_{\rm A}\) = 850 \({}^{\circ}\)C [2] & 0.000138 & & 0.484497 & 0.073327 & 0.000140 & 0.000138 \\ \hline T\({}_{\rm A}\) = 900 \({}^{\circ}\)C [3] & 0.000138 & 0.484497 & & 0.000508 & 0.000138 & 0.000138 \\ \hline T\({}_{\rm A}\) = 1000 \({}^{\circ}\)C [4] & 0.000138 & 0.073327 & 0.000508 & & 0.030820 & 0.000162 \\ \hline T\({}_{\rm A}\) = 1100 \({}^{\circ}\)C [5] & 0.000138 & 0.000140 & 0.000138 & 0.030820 & & 0.269951 \\ \hline T\({}_{\rm A}\) = 1200 \({}^{\circ}\)C [6] & 0.000138 & 0.000138 & 0.000162 & 0.269951 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: [PERSON]’s post hoc test results for hardness. DS, as-delivered state. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**State of Heat Treatment** & **[1] M = 0.79082** & **[2] M = 0.78652** & **[3] M = 0.78970** & **[4] M = 0.82289** & **[5] M = 0.90382** & **[6] M = 1.0128** \\ \hline DS [1] & & 0.999940 & 1.000000 & 0.620480 & 0.000195 & 0.000134  
findings for Hardox 500 steel. However, volumetric hardness differences alone did not fully explain wear results. For instance, steel austenitized at 960 \({}^{\circ}\)C exhibited lower mass loss than in the as-delivered state, despite its lower initial hardness. Thus, for tribological tests under high-impact conditions, microstructural morphology and subsurface mechanisms are more significant than initial hardness. Consequently, further investigation into Hardox 500 steel's impact-abrasive resistance is well justified. Representative sample wear surfaces are shown in Figure 10. Three heat treatment conditions were selected to analyze the micromechanisms at play: the as-delivered state (reference condition), quenching from 850 \({}^{\circ}\)C (highest wear resistance), and quenching from 1200 \({}^{\circ}\)C (lowest wear resistance). The surface analysis of Hardox 500 in the as-delivered state, and after quenching from 850 \({}^{\circ}\)C and 1200 \({}^{\circ}\)C, revealed different wear mechanisms directly related to the microstructure, particularly the grain size. Additionally, Figure 11a-f shows 3D images of all analyzed surfaces. Figure 8: Influence of prior austenite grain size on abrasion resistance (**a**) and hardness (**b**). In the as-delivered state and after heat treatment at 850 \({}^{\circ}\)C, conditions that demonstrated the highest abrasion resistance, abrasive wear manifests with less intense surface deformation (Figure 10a-d). In both cases, the primary wear mechanism is microplowing and plastic deformation, indicating localized plastic deformation processes due to contact with hard abrasive particles.