ORIGINAL ARTICLE Experimental investigation into lubrication properties and mechanism of vegetable-based CuO nanofluid in MQL grinding Mohammadreza Shabgard 1 & Mirsadegh Seyedzavvar 1 & Mousa Mohammadpourfard 2 Received: 30 November 2016 /Accepted: 20 March 2017 # Springer-Verlag London 2017 Abstract Application of vegetable-based nanolubricants in machining operations has been promoted due to the environ- mental concerns and higher demand for better quality of ma- chined parts. In this study, lubrication properties of copper oxide nanofluids in surface grinding of AISI 1045 hardened steel are investigated. These nanofluids were synthesized by submerged electro discharge process, exposed to ultrasonic agitation in the presence of Tween 20 as dispersant and sprayed in grinding position using minimum quantity lubrica- tion system. The base fluid is an emulsion of canola oil and distilled water with vegetable oil acting as triglyceride agent. Convective heat transfer coefficients of different lubrication systems in grinding are measured using an innovative ap- proach to better explore the cooling mechanisms involved in grinding process with or without the application of nanolubricants. The variation of grinding forces and sub- surface temperature of workpiece are recorded at different lubrication conditions. These parameters along with surface roughness, micro-hardness, and microscopic observations of ground surfaces are employed to evaluate the performance of synthesized nanofluids as lubricants in grinding. The results show that the synthesized nanofluids are effective in reducing the grinding forces and temperatures especially in extreme machining conditions. Better surface integrity of ground parts is observed in all grinding conditions through the application of CuO nanofluids as lubricant in minimum quantity lubrica- tion system. Keywords CuO nanofluid . Submerged electro discharge process . Minimum quantity lubrication . Grinding force . Surface roughness . Micro-hardness 1 Introduction Grinding is basically an abrasive process known for high energy consumption in removal of unit volume of material. This is due to the negative rake angle of abrasive grits and low depth of cut in comparison with other forms of metal cutting processes [1]. The main portion of grinding energy is converted into heat as major sources of heat in this process include sliding of flank-face of abrasive grits on the ground surface of workpiece and plastic deformation of work material. The heat generated by the friction of chips on the abrasive grits is negligible in evaluation of energy partition of workpiece during grinding [2]. To counter the nega- tive effects of heat generation during grinding process on the surface integrity of finished parts, lubrication and cooling are critical factors. The main expectations of a cooling system in grinding are reduction in the frictional losses through providing continuous lubrication film between the flank-face of grits and the ground surface and facilitation of dissipation of heat generat- ed in the contact area of grinding wheel and workpiece (contact region) [3]. The conventional approach is known as flood cooling in which coolants, generally emulsions of mineral oils, are applied with high delivery rate in the contact region during the machining process. However, the cost of recycling and dis- posal of cutting fluid is high and the environmental impacts are significant. Many restricting regulations have been enacted lim- iting the disposal of cutting fluid wastes. There are a few alter- natives to flood cooling, including cryogenic cooling, water va- por cooling, solid lubricants, and minimum quantity lubrication (MQL). MQL is a reliable substitute for flood cooling and * Mohammadreza Shabgard mrshabgard@tabrizu.ac.ir 1 Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran 2 Faculty of Chemical and Petroleum Engineering, University of Tabriz, Tabriz, Iran Int J Adv Manuf Technol DOI 10.1007/s00170-017-0319-9