• 2026-05-08
• F.O. Borokinni, O.T. Oginni, J.S. Olamide, L.A. Oseni, K.D. Alonge
• Volume 2, Issue 1

Abstract

This study investigates Citrullus colocynthis oil as a sustainable quenching medium for medium carbon steel in heat treatment. It emphasizes the creation of martensitic structures and assesses the mechanical properties of steel austenitized at 800 °C, comparing the effects of Citrullus colocynthis oil with locally sourced engine oil (SAE 40) and spent black oils. Specimens were heated at 800 °C for 30 minutes to form austenite, then rapidly quenched in oil baths to cool below 100 °C within 3–5 minutes, followed by cleaning and air drying. Synthetic oil demonstrated the highest hardness at 278.8 HV, while fresh engine oil had moderate hardness (262.9 HV) and good tensile strength (680.09 MPa). Black oil exhibited the highest tensile strength (710.00 MPa) and improved impact toughness (17.93 J), with the control sample having the best impact toughness (19.93 J). All oils enhanced hardness and tensile strength due to martensite formation, showcasing synthetic oil's hardness, black oil's strength, and fresh oil's balanced performance. Optical microstructural analysis indicated phase transformations and grain refinement, suggesting Citrullus colocynthis oil as a viable alternative to traditional petroleum-based quenching media, promoting environmentally-friendly practices in metalworking and supporting local agriculture.