The hardness of metals and alloys is a vital property which is involved in the performance of machine elements. Different heat treatment methods are used to achieve the required hardness for different applications in the manufacturing industry. However, achieving the desired hardness through heat treatment has become a significant challenge due to the lack of identification of the optimized parameters such as heating temperature, soaking time and cooling media directly affect the material’s hardness after heat treatment. In this study heat treatment process parameters are optimized for the EN19 steel material. EN19 is used widely in automobile parts gears, shafts, load-bearing tie rods, and general constructional applications where the wear resistance is of serious concern. Different quenching media (oil, water, and brine) have been used with different temperature levels (1292 °F, 1382 °F, and 1472 °F) to check the effect on the hardness of EN19 steel through the heat treatment process. The hardness of the samples were tested before and after the heat treatment process using Rockwell Hardness method. Design of Experiment (DoE) method was used to analyse the findings statistically. It is observed that the quenching media has a significant impact on the hardness at a 5% significant level. According to the results, a significant effect was obtained with brine solution compared to water but there is no significant interaction between temperature and quenching media was observed. The findings from this study provide insights into optimizing the hardening process of EN19 steel, thereby potentially reducing the costs and enhancing the efficiency in industrial applications.