<![CDATA[This study investigates the potential of shellfish shell powder as a natural source of calcium carbonate (CaCO₃) for improving the pack carburizing of AISI 1020 low-carbon steel. AISI 1020 Low-carbon steel is commonly used in engineering applications because of its favorable mechanical properties and machinability; however, its relatively low surface hardness may limit its wear resistance. Carburization was performed at 950 °C for 6 h using three conditions: an untreated control, charcoal only, and a mixture of charcoal shellfish shell powder. Surface characterization was conducted using FE-SEM/EDS, while hardness was evaluated using the Brinell Hardness test. The charcoal-shellfish shell powder specimen achieved the highest average hardness (481.44 BHN), which was significantly higher than those of the charcoal specimen (387.40 BHN) and the control specimen (216.77 BHN) (p < 0.001). FE-SEM observations showed that the charcoal–shellfish shell powder specimen exhibited distinct surface morphology, while EDS analysis revealed a higher surface carbon concentration and the presence of calcium, indicating a more effective carburizing environment than the charcoal-only treatment. These findings indicate that the shellfish shell powder effectively enhanced hardness, resulting in the formation of a carbon-enriched surface. The novelty of this study lies in the use of shellfish shell powder derived from shell waste as an alternative natural activator, and in the quantitative validation its effectiveness through statistical analysis, demonstrating its potential as a cost-effective and environmentally sustainable substitute for conventional carburizing activators.]]>
