An investigation of carbon nanofluid minimum quantity lubrication for grinding unidirectional carbon fibre-reinforced ceramic matrix composites

Abstract

Grinding is the most effective processing method for carbon fibre-reinforced ceramic matrix (Cf/SiC) composites (Liu et al., 2018). The effects of dry, flood, minimum quantity lubrication (MQL) and carbon nanofluid MQL conditions on grinding performance were studied in this research. Moreover, a method for effectively dispersing carbon nanoparticles was proposed. The experimental results showed that carbon nanofluid MQL conditions can provide significantly higher surface quality and lower grinding forces than the dry, flood and MQL conditions. In addition, the nanofluid poses a negligible threat to the environment and to workers, which means that carbon nanofluid has good application prospects in grinding processes. The influences of the nanoparticle concentration, air pressure, flow rate, nozzle distance and nozzle position on the grinding forces and surface quality were also investigated in this paper. According to the experimental results, the optimum parameters can be concluded as follows: the nanoparticle concentration was 5 g/L, the air pressure was 7 bar, the fluid flow rate was 80 mL/h, and the nozzle distance was 60 mm. According to the ground surface microtopography, matrix cracking, fibre pullout and fibre outcrop were the primary defect forms. In the grinding process, the debonding depth between the matrix and the carbon fibre depended on the sharpness and lubrication state of the abrasive grains. Long fibre debris, short fibre debris, fibre microparticles and SiC particles were the basic components of the grinding debris according to scanning electron microscopy (SEM) micrographs of the typical grinding chips from the Cf/SiC composites. This research is expected to investigate the application potential of carbon nanofluid MQL and propose a greener and more efficient lubrication method.