The effects of energizer, carburizing temperature and time on the mechanical properties of hardened big knives in a pack carburizing process

Abstract

The purpose of this research is to study the effects of energizer, carburizing temperature and time on the mechanical properties of hardened big knives in a pack carburizing process. The mechanical properties of carburized and hardened big knives were compared to those of commercial hardened big knives made from leaf-spring steel that were forged, ground and quenched following traditional processes. The experiment was conducted by forging big knives made from low carbon steel (grade AISI 1010). The first group of them was then pack-carburized using 10 wt% of calcium carbonate with 90 wt% of eucalyptus charcoal. The second group used 10 wt% of egg shells with 90 wt% of eucalyptus charcoal. The carburizing temperatures were 900, 950 and 1,000 °C, with carburizing times of 30, 60 and 90 minutes followed by air cooling. The austenitizing temperature was 780 °C with a holding time of 20 minutes, followed by quenching in water. Finally, the big knives were tempered at 180 °C for 1 hour. Micro-Vickers hardness testing, impact testing and microstructure inspection were carried out. The results of this experiment showed that the hardness of hardened big knives increased with increasing carburizing temperature and time, while its impact value decreased. The hardness derived from using CaCO₃ was slightly more than that using egg shells, however, the impact energy was higher when using egg shells compared to using CaCO_3.