In the present study material low carbon steel ASTM A36 were treated with pack carburizing with carburizing agent, a mixture of gigantochloa apus (Schult.F.) Kurz charcoal (GAC) and pomacea canalikulata Lamarck shell powder (PCSP). The composition of carburizing agent PCSP-GAC was varied at 10%: 90%, 15%: 85%, and 20%: 80%. The process done at carburizing temperature various 875, 900, 930 ℃ and soaking time for 2 hours. The surface hardness test and an impact test was carried out to determine changes in the surface hardness number and impact toughness. From the results of the study, it was concluded that pack carbrizing with carburizing agent, a a mixture of PCSP and GAC increased the hardness number but decreased the impact toughness of the specimen. The highest hardness number is 537.48 Kg/mm², the lowest impact toughness is 158.33 Joules, at a pack carburizing temperature of 930 ⁰C, the composition of the carburizing agent 20% PCSP : 80% GAC. Microstructural characterization indicates that high toughness of the carburizing steel subjected to the cooling heat treatment process results from a proper multiphase microstructure transition from the surface to the matrix of the steel.
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