Performance evaluation of GNPs-Cu/ZrO2 multicomponent hybrid nanofluids in MQL-assisted turning of Inconel 718

Abstract

Inconel 718 superalloys are considered as a hard-to-cut material for their low thermal conductivity which is responsible for high cutting temperature, inferior surface quality and serious tool wear. To reduce the cutting temperature and tool wear during the minimum quantity lubrication (MQL) assisted machining process of Inconel 718, graphene nanoplates (GNPs)-copper (Cu)/zirconium oxide (ZrO₂) multicomponent hybrid nanofluids (NFs) were prepared using GNPs-Cu nanocomposites and ZrO₂ nanoparticles as soft and hard phase respectively. Firstly, GNPs-Cu nanocomposites were prepared by oxidation-reduction method and characterized. Then, investigations about the wettability, viscosity, thermal conductivity of prepared hybrid nanofluids were carried out and performance in MQL-assisted turning of Inconel 718 were analyzed. Results show that wettability and thermal conductivity of lubricant increase by 57.76 % and 38.87 % respectively with the addition of GNPs-Cu/ZrO₂ (2:1) hybrid nanoparticles compared with that of base oil. Owing to the excellent performance in cooling and lubrication of hybrid NFs, the cutting temperature and the cutting force were significantly decreased and the finish of the machined surface was improved under hybrid NFs MQL-assisted cutting. Besides, the tool wear was decreased by 30.02 % when cutting the same distance compared to that of base lubricant. The analysis of tool wear indicated that the optimal hybrid NFs can not only greatly diminish the adhesive wear but also prolong the tool life. The GNPs-Cu/ZrO₂ nanoparticles can enhance the formation of stable tribo-film with high load-bearing capacity through the outstanding lubricity of GNPs, surface repairing of soft nanoparticles (Cu) as well as the polishing and ball-bearing effects of hard particles (ZrO₂).