Development and characterization of Putranjiva roxburghii with addition of SiO 2 and graphene nanoparticles for using it as a cutting fluid

Cutting fluids are used in the machining to lubricate and cool the tool-workpiece combination. Recent trend is to use vegetable oils as cutting fluid in place of synthetic oils to ensure sustainability. This work explores the lubrication ability of Putranjiva roxburghii vegetable oil by adding suitable proportions of silicon dioxide (SiO₂) and graphene nanoparticles for achieving the goal of sustainable machining. Pure base oil was obtained from the seeds of the Putranjiva roxburghii tree by the conventional extraction process. Nanoparticles of SiO₂ and graphene were mixed separately in different weight percentage, viz., 0.25%, 0.5%, 0.75%, and 1% to prepare the nanofluids. Nanofluids with equal proportions of SiO₂ and graphene nanoparticles were also prepared. Characterization techniques were employed to properly examine the structure and composition of nanoparticles. Thermal, rheological, and wettability tests were conducted for prepared nanofluids. The properties of the nanofluids were superior to those of the base oil. It was noted that no single concentration of nanoparticles is the best for all properties. For example, the highest thermal conductivity was obtained for 0.75 wt.% of graphene-dispersed nanofluids. On the other hand, the wettability on inconel 718 was the highest for graphene plus SiO₂ nanofluids at concentrations of 0.5 wt.%. Hence, the optimum composition of cutting fluids can be obtained by solving a multi-objective problem depending on the need of machining. The efficacy of the developed bio-based nanofluids was tested during the milling of Inconel 718 by evaluating surface roughness and temperatures. The results were compared against dry machining and base oil-wetted conditions to assess its performance. Putranjiva roxburghii based hybrid (SiO₂ + graphene) oil performed better.