Analysis of the Effect of Saltwater (NaCl) Solution Concentration During the Quenching Process on the Microstructure and Hardness of Medium Carbon Steel

This study analyzes the effect of sodium chloride (NaCl) solution concentration on the hardness and microstructure of medium-carbon steel. The heat treatment process was carried out using the hardening method, which included pre-heating at 600 °C for 30 minutes and austenitization at 850 °C for 25 minutes. The samples were then quenched in NaCl solutions with concentrations of 0%, 5%, 10%, and 15%. Analysis using the Spark-OES method revealed that the samples contained 0.303% carbon. The results showed that the NaCl solution concentration influenced the hardness by 71.73% and the toughness by 45.03% in medium-carbon steel. Furthermore, the hardening process induced a phase transformation from ferrite (α) and pearlite to martensite.