Lubricity Assessment of Neem and Castor Oils and their Blends in Machining Mild Steel
Mineral oil and sulfonates have been the basic source of cutting fluid formulations, but their uses have been questioned nowadays as regards to cost, health and environmental issues. The use of vegetable based cutting fluids is increasing and minerals based cutting fluids are likely to be replaced with vegetable based cutting fluids. The present study assessed the lubricity of blended oil from Castor and Neem seeds. These oils were extracted by mechanical method. The blends were formulated by varying the amount of each oil in the blend to see its effect in the properties and characteristics of the oil. The oil obtained was investigated for physicochemical parameters and fatty acid profiles. The fatty acid in Neem oil showed the presence of oleic acid (41.9%), linoleoic acid (19.50%), stearic acid (18.68%), palmitic acid (15.56%) linolenic acid among others, while that of Castor oil had palmitic (0.46%), Stearic (0.72%), Linoleic (4.4%), Linolenic (0.2%), Dihydroxylstearic acid (0.69%) and ricinoleic acid (90.58%). Lubricity of the formulated cutting fluid was tested using four balls tribo meter tester and the results obtained showed minimum Wear Scar Diameter of 0.13 mm which is the least among the formulated oils obtained in the 60% Neem and 40% Castor oil; this implies that this formulation has maximum lubricity in terms of friction reduction as compared to other formulated oil and the conventional soluble oil available in the market. This combination was found to be the optimum sample compared to other blends.
The formulated cutting fluids were further tested in machining mild steel. The chip thickness formed using the formulated cutting fluid at 90rpm was found to be 0.203 mm which is higher than that of the conventional cutting fluid obtained as 0.17 mm at constant depth of 2 mm; the high chip thickness value is due to its better lubricity property which allows for better metal removal rate, good surface finish and continuous chip formation.
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