THE USE OF SELECTED BIOMATERIALS AS ENERGISER IN SURFACE HARDENING OF MILD STEEL

Abstract

Surface hardening is an essential heat treatment given to gears, shafts, cutting tools and other machine components to impact on them a good wear resistance surface. The kinetics of the depth of diffusion of carbon in mild steel is usually enhanced by the addition of an energizer such as barium carbonate (BaCO,) in the hardening mix. Barium carbonate is not locally available in Nigeria. Investigation were therefore carried out to appraise some agricultural waste: cow bones, coconut shells and sea shells for use as energizers in surface hardening of mild steel. Packed-carburization technique was used and various compositions of the carburizing mixture were investigated. At 900°C, optimal values of surface hardness were obtained at 20% cow bone and 30% sea shell additions. Coconut shell did not seem to significantly influence the hardening process at any level of addition. The results showed that cow bone was 65.5% as efficient as BaCO,, while sea shell was 82.5% efficient. This paper presents the effects of energizer concentration, chemical compositions and holding time on the kinetics and quality of the hardened products.