Abstract
A comparative study was carried out to investigate the suitability of some selected Nigerian vegetable oils as alternative quenchant to SAE40 engine oil for industrial heat treatment of Medium Carbon steels. The study involved the characterization of physicochemical properties and fatty acid profile of cotton seed oil, palm kernel oil, neem seed oil and palm oil. The quenching performance of these vegetable oils was conducted at quenchant bath temperatures of 34oC, 50oC, 70oC, and 100oC. SAE40 engine oil (Standard quenchant) and tap water served as control. The effect of cooling rates of the quenching media on mechanical properties and microstructure of the quenched steel samples were investigated. The results obtained show that the different vegetable oils have different viscosity and viscosity-temperature behavior just as their molecular structures were different. The mechanical properties of the as-quenched specimens in these oils show that the hardness of steel quenched in palm kernel oil was highest 40.85HRC. As received sample absorbed the highest amount of energy (183 J) before fracture while sample quenched in water absorbs least energy (28 J). Hence vegetable oil is suitable as alternative quenchant to petroleum based SAE40 engine oil for quenching medium carbon steels, without cracking or distortion, the most suitable among them being palm kernel oil.
Highlights
Most steel parts such as gears, precision guages, bearings, tools and dies produced today are heat treated before being put into service
The physicochemical properties and the fatty acid ester compositions of the quenching media are entered in Table 2 and Table 3 respectively
The various microstructures developed after quenching the carbon steel in selected quenching media are presented in Table 4 and Micrographs 1-7
Summary
Most steel parts such as gears, precision guages, bearings, tools and dies produced today are heat treated before being put into service. Parts are heat treated to enhance particular properties, such as hardness, toughness and corrosion resistance, and to improve uniformity of properties. The exact heat treatment applied depends on both the type of alloy and the intended service conditions [1]. The main types of heat treatments often used to modify the microstructure and mechanical properties of engineering materials steels are annealing, normalizing, hardening and tempering [2]. Quenching of steels involves the process of heating a part above upper critical temperature to austenitizing temperature and holding at this temperature for a specified soaking time followed by intense cooling in a suitable quench medium. Quenching prevents the formation of ferrite or pearlite and allows the formation of bainite or martensite [3]
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