Effects of reinforced nanoparticles with surfactant on surface quality and chip formation morphology in MQL-turning of superalloys

Abstract

Superalloys (nickel and titanium-based alloys) are grouped as difficult-to-cut materials. Therefore, due to poor machinability of superalloys, their machining is a great challenge for manufacturing sectors. Surface quality of work part and chip formation morphology are considered as the main machinability attributes in machining superalloys. Although numerous studies have been focused on this context, however, no work was found on the effect of nanoparticles stability on nanofluid performance and consequently on machinability attributes, in principle surface quality and chip formation morphology. In the present study, the importance of nanoparticles stability by adding of surface active agent (surfactant) as additive elements was evaluated. Two kinds of nanoparticles including nano copper-oxide and nano silicon-oxide with different volume fraction were used to prepare nanofluid solution. In addition, surfactant from the group of Sodium Dodecyl Sulfate (SDS) which is appropriate for polar fluid was selected. Scanning Electron Microscope (SEM) images were utilized to analyse the machined surface of the work part. Cutting fluids were prepared in three conditions, including nanofluid with surfactant (reinforced nanofluid), nanofluid without surfactant, and conventional cutting fluid (without nanoparticles). The average surface roughness Ra was considered as the surface quality attribute. The recorded values of Ra and chip formation morphology indicated that reinforced nanofluid could significantly improve the cutting mechanism as compared with nanofluid without surfactant and conventional fluid. The main reason for this phenomenon can be attributed to high ability of surfactant to disperse nanoparticles in the fluid medium as well as high capability to prevent nanoparticles aggregation. After a short period, the nanoparticles in nanofluid without surfactant attached to other particles and a massive mass (nanoparticles aggregation) was formed which led to quick settling of nanoparticles. By settling of nanoparticles, the environment becomes free of nanoparticles and similar properties and capability as conventional fluid may occur.