1.1 Background Information
Most engineering materials have unique properties that render them useful in many applications. Before any engineering material is subjected to used, it must satisfy certain range of properties suitable for that purpose, the usage is determined by its availability, cost, corrosion, wear resistance, durability and other functional requirement (Linus and Ihom, 2013). Mild steel is one of classes of steel that contain low quantity of carbon about 0.1-0.25% and it has a density of 7850kg/m3. Mild steel has wide range of application in the production of engineering element like gears, cam, shaft, pinions, keys etc, in developing countries like Nigeria, mild steel is commonly used for machinery construction because of its availability, dominance, workability, ductility, cost-effectiveness, wear resistance etc among the class of steel (Ihom and Aniekan, 2014).
There are numerous limitations encountered in the usage of the mild steel particularly as regarding wear resistance, hardness and strength, most machines constructed in the developing world like Nigeria using this engineering material, do not last long especially when moving components of the machine like gear, shaft, valves, disc, cam etc which requires a tough core and a hard surface are constructed of mild steel without casehardening heat treatment (Ihom, Nyior Alabi, Segun Ogbodo, 2012).
According to Ihom and Aniekan, (2014), casehardening of a material can be accomplished by subjecting the component to high temperature in the presence of a carbonaceous material which may be solid, liquid or gaseous, energizer are often used to speed up the process. It is a process used to produce a high surface hardness for wear-resistance supported by tough, shock-resistance core. It is also the process of saturating the surface layer of steel with carbon to about 0.19% or some other process by which case is hardened and core remain soft. A survey of Nigeria industrial stock market reveal a dearth of commercial pack carburizing compound that fabricators, machinist and blacksmiths who produce or recondition these vital engineering element could conveniently use to carburize or case harden them. The resultant effect of this is the non-treatment of such produced parts with the consequent results of fast wear, tear and failure of the parts made up of mild steel (Dempsey, 2002).
Production of case hardening compound for surface treatment of mild steel using different local carbonaceous material cannot be overemphasized. This is because of machine component fabricated from mild steel, when subjected to friction, it easily get wear and tears, for effective usage of the machine part, the mild steel can be subjected to casehardening compound formulated from local carbonaceous element like coal, bone, charcoal, snails shell, periwinkle shell, above all, the hardness of mild steel pack carburized with each of the local carbonaceous element above will be determined, also the case depth will be determine.
Case hardening is the process that is used to harden the outer layer of case hardening steel while maintaining a soft inner metal core. The case hardening process uses case hardening compound for the carbon addition. Case hardening is a technique in which the metal surface is reinforced by the addition of a fine layer at the top of another metal alloy that is generally more durable. Case hardening steel is normally used to increase the object life. This is particularly significant for the manufacture of machine parts, carbon steel forgings and carbon steel pinion. Case hardening is also utilized for other application. Case hardening has been in use for many centuries and was frequently used for producing horseshoes and different kinds of cooking utensils that were subjected to substantial wear and tear. Case hardening is performed normally on top surface and for a limited depth. Greater hardness is usually related with cover wear and fatigue resistance (Ogo and Ette, 1994).