Synergistic Effects of Multiphase Composite Nanofluids Minimum Quantity Lubrication and Cryogenic Cooling on the Machining Performance of Gh4169

Abstract

Although nanofluids minimum quantity lubrication (NMQL) can reduce tool wear and improve the surface quality, there still exist the problems of limited cooling effect and thermal decomposition failure of lubricating film during the high-speed cutting of hard-to-cut materials. Compared with NMQL, cryogenic MQL and cryogenic NMQL can provide both effective lubrication and substantial reduction in cutting temperature. However, limited researches have been conducted on cryogenic multiphase composite nanofluids (NFs) MQL for machining hard-to-cut materials. In this work, an attempt was made to study multiphase composite NFs MQL cutting of GH4169 under liquid nitrogen (LN2) cryogenic cooling. The nano fluids incorporating GNPs-Cu (soft)/ZrO2 (hard) multiphase composite nanoparticles with different Cu-loaded content were developed, while the friction and wear performance of the prepared NFs and wear mechanisms were investigated. The friction coefficient and wear rate were reduced by 60.33% and 27.01% under GNPs-Cu/ZrO2 multiphase composite NFs with Cu-loaded content of 20 wt.%, respectively, compared to those under pure base oil. Subsequent turning of GH4169 experiments under dry, MQL, NMQL and LN2+NMQL conditions demonstrated that the longest tool life (2200 mm), the best machined surface quality (0.433 μm), the lowest cutting temperature (52 ℃) and cutting force (212 N) were achieved under LN2+NMQL condition. Additionally, adhesion wear oxidative wear of tool were further reduced under LN2+NMQL compared to that under NMQL. The load-bearing capacity of the GNPs-Cu/ZrO2 NFs self-assembled lubricating film was enhanced due to the low temperature environment provided by LN2.

Keywords: Cryogenic cooling, NMQL, GNPs-Cu/ZrO2, Cutting performance, Wear mechanisms