PRELIMINARY STUDY OF SELECTION OF ENVIRONMENTALLY BENIGN LUBRICANTS FOR CONVENTIONAL AND SEVERE PLASTIC DEFORMATION PROCESSES

Abstract

The purpose of this paper is to investigate the suitability of some environmentally benign
lubricants for the processing of conventional and severe plastic deformation operations. Al 6063
bar was annealed at 350"Cfor l hr, machined and cut to billets size of 14 tnm x 14 mill x 44 min.
These specimens for extrusions were machined to the specified dimensions to visibly good

. finishes. The billets were extruded through a twisted and direct equal channel angular extrusion
(ECAE) dies of 14 x 14 mil? channel cross-section area. The channel angle was 12(J', the angle of
the outer arc of the channels was 3D" . The deformation area of the die was slightly twisted to
impact additional strain. The puncli and container used for the experiment were made of tool steel
alloy A/SI D2, and were chromium-coated and polished. Seven lubricants such as palm oil,
tropical coconut oil, palm kernel oil, soya oil, mustard oil, groundnut oil and sesame oil lVere
used in this study. Also, a double cup extrusion test (DCET) was performed using tire same
alum ill III II, but for annealed and non-annealed billets to represent, respectively, the normal and
adverse conditions {hat exist ill conventional and ECAE processes. The results obtained front the
experimental works show that red palm oil has satisfactory lubrication performance ill both
conventional metal forming processes and severe plastic deformation. But groundnut oil performs
satisfactorily well in conventional metal forming processes but failed under severe plastic
deformation (SPD) whereas, olive oil performed poorly in conventional processes but suitably
well in severe plastic deformation. 'The higher the strain rate the higher the load during severe
plastic deformation processes. Also, it is found that while the values of strain hardening exponent,
n, decreases with increasing deformation rate, strength coefficient, k, increases. The current
experimental work successfully select, simultaneously, some vegetable-based oils such. as soya,
red palm, mustard, tropical coconut, and palm kernel oils as good replacements for petroleum-
based lubricants for conventional and SPD metal forming operations.