Machinability investigation of grinding 2.5D-SiCf/SiC composites under nanofluid minimum quantity lubrication

Abstract

SiCf/SiC composites are now the preferred option for the thermal structures of next-generation advanced aero-engines, owing to their high-temperature strength, and creep resistance. Grinding is currently a highly reliable and mature method for SiCf/SiC processing. However, the harsh, dry machining conditions lead to degradation of surface quality, and the dust generated can harm both humans and the environment. Nanofluid Minimum Quantity Lubrication (NMQL) maximizes heat transfer and lubrication in grinding and is environmentally and human-friendly. Based on this, this study thoroughly investigates the effects of dry, flood grinding, minimum quantity lubrication, and different nanofluids (MoS2 and carbon nanotubes (CNTs)) on grinding performance at different grinding depths. Compared with dry grinding, the results show that the normal grinding component force Fn is reduced by 56.9 %, 56.8 %, and 71.6 %, and the tangential grinding component force Ft is reduced by 48.4 %, 50.5 %, and 57.5 % for NMQL-CNTs lubrication condition at grinding depths of 0.2 mm, 0.4 mm, and 0.6 mm, respectively. Meanwhile, NMQL-CNTs can significantly improve the surface quality and help to obtain a surface morphology with fewer surface defects, and the stabilized lubricant film formed by NMQL-CNTs can significantly reduce the specific grinding energy. Although brittle removal was observed in different lubrication methods, NMQL-CNTs could significantly reduce surface damage due to their filling and friction reduction effects. Due to the high viscosity of NMQL-CNTs and the low intermolecular forces, they have strong lubrication stability and wear resistance. This study provides theoretical guidance for the green processing of SiCf/SiC composites.