# The Influence of Grain Size on the Abrasive Wear Resistance of Hardox 500 Steel
## 4 Conclusions  
This study aligns with current research trends focused on modern steel groups with enhanced abrasion resistance. In microstructural analysis, austenite grain growth is pivotal, as grain size directly influences phase transformation kinetics. The microstructure is closely correlated with key mechanical properties, including hardness, yield strength, tensile strength, and impact resistance. Additionally, grain size significantly impacts tribological resistance in Hardox 500 steel, making precise grain size control during heat treatment essential for optimizing mechanical properties and durability. This research yielded the following conclusions:  
1. Prior austenite grain size shows a clear correlation with austenitizing temperature, described by an exponential function. At lower temperatures (850-900 \({}^{\circ}\)C), the grain remains fine, while grain growth intensifies above 1000 \({}^{\circ}\)C, I leading to a significant increase in average grain diameter to over 100 \(\upmu\)m after austenitizing at 1200 \({}^{\circ}\)C.
2. Hardox 500 steel in the as-delivered state exhibits a homogeneous martensitic microstructure with a three-tier hierarchical structure. Increasing the heat treatment temperature consistently produces a uniform martensitic structure. The presence of martensitic lambs and needles, which are more strongly etched, may indicate chemical composition microsegregation, resulting in carbon-enriched microareas. 3. Selecting the appropriate heat treatment temperature is critical to optimizing both the abrasion resistance and hardness of Hardox 500 steel. Increasing the heat treatment temperature, which leads to coarse-grained structures, significantly reduces its wear resistance. Notably, even after heat treatment at 1200 \({}^{\circ}\)C, the steel's hardness was over 8% higher than in the as-delivered state. These results highlight the essential role of austenitizing in controlling the mechanical properties of steel, and they emphasize that heat treatment can enhance abrasion resistance through increased hardness relative to the initial material, provided that grain size is controlled to prevent the formation of abnormal grain. 4. The relationship between grain size and wear intensity was approximated by a quadratic function with an \(R^{2}\) value of 0.82. Meanwhile, the correlations between average grain size and hardness, as well as between hardness and abrasion resistance, were better represented by quadratic functions with higher \(R^{2}\) values of 0.97 and 0.87, respectively. 5. The primary wear mechanisms for Hardox 500 in the as-delivered state and after quenching at 850 \({}^{\circ}\)C are microplowing and plastic deformation. After quenching at 1200 \({}^{\circ}\)C, the surface shows significantly greater wear intensity, with deeper and more numerous pits and fine scratches oriented at various angles to the direction of abrasive particle movement. 6. Plastic deformations, and consequently the retention of martensitic microstructure ductility despite high hardness, play a crucial role in abrasion resistance. The observed deformations and pits are highly dependent on grain size, with the largest ones appearing in Hardox 500 steel subjected to the highest heat treatment temperatures (1100 \({}^{\circ}\)C and 1200 \({}^{\circ}\)C), due to greater susceptibility of the microstructure to intense abrasive action. 7. Austenitizing temperature also affects the surface roughness of steel after abrasive wear testing. Lower temperatures, particularly 850 \({}^{\circ}\)C and 900 \({}^{\circ}\)C, yield smoother surfaces with lower roughness, whereas austenitizing at 1000 \({}^{\circ}\)C and 1200 \({}^{\circ}\)C increases roughness parameters, particularly \(Rz\), \(Rp\), and \(Rv\), compared to the as-delivered state. An austenitizing temperature of 1100 \({}^{\circ}\)C provides low roughness parameters, though this does not directly translate to improved functional properties, as represented by abrasion resistance in this treatment state. 8.