Evaluation of Local Vegetable Oils as Quenchants for Hardening Process in Grey Cast Iron

The hardening characteristics of grey cast iron quenched in some locally available vegetable oils (groundnut, palm kernel, shea butter and Soya bean oils) have been studied using hardness values, tensile properties and impact values as major criteria. On a comparative basis, hardening characteristics of grey cast iron quenched in SAE40 engine oil – a good commercial quenching medium – was also studied for hardening process. Microstructural examination revealed, principally, lower bainite and martensite in all the quenched grey cast iron specimens. The mechanical properties of groundnut oil, shea butter oil, soya bean oil and SAE40 engine oil quenched grey cast irons are found to be superior to that obtained for palm kernel oil quenched cast iron, but their wear resistance as shown by the hardness values are inferior to that of palm kernel oil quenched cast irons. However, the wear resistance of the quenched grey cast iron developed in this group of local vegetable oils was superior to that of SAE40 engine oil. The potentials of these oils as quenching media for grey cast iron hardening process ranked in descending order as soya bean, shea butter, groundnut, and palm kernel, with respect to tensile strength values. In general, excellent hardening properties were obtained with these locally available vegetable oils. Hence, the suitability of these oils as a better quenching media than SAE40 oil in hardening process of grey cast iron has been ascertained. Keywords: Graphite flakes, grey cast iron, hardening, mechanical properties, microstructure, vegetable oils.