ABSTRACT
The suitability of hardwood charcoal and snail shell particles for carburizing mild steel was investigated. All the mild steel specimens were carburized at constant temperature of 920�C from one (1) to five (5) hours at intervals of one hour. The mild steel specimen in the as-received and carburized conditions were all prepared for the following tests: hardness, impact and microstructure examination. The outcome of the test shows that the as-received specimen has the least hardness value (191Hv) followed by 100% charcoal which showed hardness of 493Hv for the case and 280Hv for the core. The case also showed increases in hardness as pulverized snail shell and charcoal is added in weight percentages of 5%-95%, 10%-90%, 15%-85%, 20%-80% and 25%-75%. The highest hardness value were observed for combination of weight percentage 75% charcoal and 25% pulverized snail shell which gave a case hardness value of 765Hv and core hardness value of 314Hv. The hardness of both the case and the core for all carburized steel samples increases with holding time in the furnace. The case depths also showed a trend similar to the hardness values with holding time, for the combination of weight percentage 25% snail shell the case depth increases from 0.6mm to 1.6mm with increase in holding time from 1hr to 5hrs. In the as-received condition, the impact strength obtained was 70J while in the carburized and quenched hardened condition the impact strength obtained was 78J. However on tempering the impact strength obtainedwas 74J. The microstructure of the steel specimen in the as-received condition is predominantly pearlite in a matrix of ferrite. However, the carburized steel specimen showed varying degrees of carbide, indicating increased carbon content at the surface.