The influence of turning parameters on the surface integrity of the workpiece in hard turning of AISI 52100 steel using minimum quantity lubrication (MQL), was investigated in this work. The cutting parameters considered were cutting speed, feed, depth of cut and tool nose radius, at three levels each. Response surface methodology was employed to study the influence of factors on surface roughness, microhardness, topography, white layer thickness and elemental composition. From model analysis, the microhardness and surface roughness were best predicted by quadratic regression models, whereas white layer thickness was best evaluated by a linear model. The variance analysis revealed that surface roughness was significantly affected by nose radius (33·83%), followed by feed (32·5%). It was observed that surface defects were reduced with an increase in cutting speed. Microhardness was majorly affected by feed (36·64%), followed by nose radius (32·88%). The white layer thickness ranged from 4·3 to 15·9 μm for all experiments. White layer thickness was significantly influenced by nose radius (82·24%), cutting speed (9·78%) and feed (1·23%). Energy-dispersive X-ray spectroscopy analysis of the machined workpiece at a cutting speed of 150 m/min validated that oxidation was instigated and the weight percent of carbon was augmented in the base metal.

In the present study, boron carbide (B4C) and boron nitride (BN) nanoparticles combined in equal proportions and reinforced into aluminium 7010 alloy with 0–2.5 wt.% nanoparticles in intervals of 0.5 wt.% were prepared using the ultrasonically assisted stir-casting technique. Microstructural characterisation of the composites was carried out by using a scanning electron microscope and an X-ray diffractometer. The tensile strength was determined using an Instron testing machine. The tensile strength of the nanocomposites increased with the increase in the weight percentage of nanoparticles up to 2 wt.% and thereafter decreased. It was observed that the percentage of elongation decreased with the increase in reinforcement up to 2 wt.% and thereafter increased. The density of the hybrid metal matrix nanocomposites decreased with the increase in boron carbide and boron nitride nanoparticles. The porosity increased with the increase in the weight percentage of boron carbide and boron nitride nanoparticles. X-ray diffraction results indicated that aluminium, boron carbide and boron nitride were the principal elements of the composites and the components were free of intermetallics.