Effect of bio-mineral oil blend quenchant on the mechanical properties of carburized mild-steel

Abstract

In this study, the effect of bio-mineral oil blend quenchants on the mechanical properties of carburized mild steel was experimentally studied and reported. The tensile, hardness, impact, and microstructural test specimens were prepared in line with ASTM standards. Prepared specimens were then buried in a 50:50% ratio mixtures of eggshell/date-seed particulates as carburizing medium in a sealed packed cylindrical crucible. The carburization was then carried out in a muffle furnace at 950 oC for 3 h soaking time at 5 °C/min heating rate and thereafter quenched in different percentage blends of bio-mineral oils. Before the mechanical test and microstructural examination, samples were tempered at 200 oC for 1 h.Results from the experimental findings revealed that water and bio-mineral oil blend quenchants significantly influenced the mechanical properties and microstructure of carburized mild steel in varying degrees depending on the quenching media. Specimen quenched in 100% groundnut oil yielded the maximum yield tensile strength (805.43 MPa) and hardness at the surface edge (173.8 HV) equivalent to 106.7 and 87.66 percentage increment however, the best combination of mechanical properties (tensile strength 738.66 MPa, strain 17.12%, hardness 169.5 HV and impact strength 51.1 J) was obtained in the specimen quenched in 60/40% groundnut oil and SAE40 oil blends respectively. The enhancement in the mechanical property was due to the grain refinement in the microstructure of the bio-mineral oils quenched specimen. The 60/40 groundnut/SAE40 oil blend is therefore recommended for metallurgical heat treatment of mild steel for critical industrial applications.