Experimental Study of Surface Integrity of Al/SiC Particulate Metal–matrix Composites in Hot Machining

Abstract

Al/SiCp Metal Matrix Composites (MMCs) are the new class of materials and are rapidly replacing conventional materials in various applications industrial and aerospace applications. These materials are generally regarded as extremely difficult to machine, because of the abrasive characteristics of the reinforced particulates. It has poor machinability such as excessive tool wear and fracturing of the reinforcement particles on machined surface. It leaves behind adhered particle fragments, pits and cavities despite superior excellent engineering properties. These characteristics in machining of Al/SiCp MMCs tend to adversely affect the machined surface quality/integrity. Hence, an attempt is made to improve the machinability of Al/SiCp MMCs and surface quality by hot machining. This paper presents the results of an experimental research on hot machining of Al/SiCp MMCs produced by stir casting. PVD coated carbide inserts were used under dry cutting conditions. Experiments were carried out on CNC lathe. Experiments on Al/SiCp 10% composites of two different particle size of Silicon carbide reinforcement i.e. coarse and fine (220 and 600 mesh size respectively) are performed using L16 orthogonal array as per the Taguchi method. The study of Al/SiCp MMCs on the basis of surface integrity was tried out in order to know the machinability. The experimental study showed that feed, depth of cut and preheating temperature have a significant influence on cutting force, feed force, thrust force, surface roughness and micro-hardness variation beneath the machined surface. The micro-hardness is found to be higher near the machined surface layer and decreases with the depth of machined subsurface for all experimental conditions. Qualitative analysis of surface and subsurface damage is analysed using SEM photographs. A SEM photograph reflects the SiC particulates debonding, fracture, feed marks and smeared layer on machined surface. Better values of surface roughness are obtained at 60°C temperature during machining of both Al/SiC/10p/220 (0.776μm) and Al/SiC/10p/600 (0.640μm) MMCs.