Investigations on Machining Characteristics of Metal Matrix Composites Using Abrasive Flow Machining

Abstract

In the era of non traditional finishing processes, it is of upmost importance that these processes can be applied to composite materials, as they have replaced traditional materials in many applications. It is hard to finish small slots in composite materials which have wide applications now days in aerospace, automobile, medical industries etc. Composite materials have replaced the traditional materials as their properties like light weight, good strength and good economy are of unique benefits. Abrasive Flow Machining (AFM) is an advanced finishing process suitable for machining difficult to reach and machine surfaces. In the literature, work has been reported on Abrasive Flow Machining of materials like Aluminium, Brass and EN8, etc. In the present work AFM set up has been designed and developed in the laboratory for experimental work. Composite materials with a high percentage of SiC (like 20-60 % SiC in Al/SiC composites) have been machined using abrasive flow finishing. Taguchi methodology is applied to find the effect of input parameters (Fluid pressure, percentage of oil in media, grit size, concentration of abrasives, work piece material and number of cycles) on the material removal rate (MRR), change in surface roughness (ΔRa) and surface topography. L27 array has been designed for experimental work. It is observed that extrusion pressure is the most significant factor for MRR and ΔRa. Optimization of response parameters (MRR and ΔRa) is done using Taguchi method. Further Response Surface Methodology (RSM) is also applied for experimental investigation. Box-Behnken design has been selected. Response parameters have been optimized using the desirability approach. The significance of different parameters is identified using ANOVA. An optimum combination of parameters is designed for the process. Mathematical modeling has been done for material removal rate using FEM and mechanism of material removal in abrasive flow machining has been also discussed. Specimens were examined and analyzed using scanning electron microscope and X- ray diffraction techniques. Work pieces cut by EDM process were finished by AFM process. It was observed that abrasive flow machining has removed the defects and improved the surface finish significantly.