An investigation on application of nano-fluids in high speed grinding of sintered alumina

Abstract

Ceramics are the most sought-after materials in various advanced engineering applications. Diamond abrasive machining is used to achieve dimensional tolerances for hard ceramic materials. Micro-brittle fracture and grain dislodgement are the primary material removal mechanisms which generate surface and sub-surface defects. High processing cost and manufacturing defects limit their widespread use. This paper investigates the effectiveness of different grinding environments in reducing the brittle fracture in high speed grinding of highly pure and dense alumina work samples using single layer electroplated diamond grinding wheel. Grinding environments included straight cutting oil, water soluble oil at 5% concentration (soluble oil), and two water based nanofluids of alumina and hBN, all in Minimum Quantity Lubrication (MQL) mode. Conventional flood cooling with 5% concentration of soluble oil in water was used as the benchmark. Grinding forces were measured to estimate the specific grinding energy and apparent coefficient of friction. Surface integrity aspects of ground samples such as surface morphology, surface roughness and residual stresses were studied using Scanning Electron Microscope (SEM), 3D surface profilometer and x-ray diffractometer, respectively. Morphology of the grinding wheel was studied using stereo zoom microscope. Based on the experimental observations, a new model is proposed to demonstrate the interaction of nanoparticles in the grinding zone for grinding of brittle materials including alumina. Results showed that the nanofluid MQL yielded highly fractured surface because of high contact stress fields, whereas straight cutting oil MQL provided better lubrication in the grinding zone which promoted ductile deformation. Compressive residual stresses of the order of 105 MPa were observed in the samples ground with straight cutting oil MQL which can improve the fatigue life. Single scratch experiments done using diamond indenter also showed better lubrication efficiency of the straight cutting oil in comparison with soluble oil.