Enhanced machinability of SiC-reinforced metal-matrix composite with hybrid turning

Wei Bai,Anish Roy,Ronglei Sun,Vadim V Silberschmidt

doi:10.1016/j.jmatprotec.2019.01.017

Abstract

Particle-reinforced metal-matrix composites are promising engineering materials thanks to their superior mechanical and thermal properties. However, their poor machinability is a deterrent for use in wider applications, due to the presence of hard ceramic particles, which results in rapid tool wear during machining. Ultrasonically assisted turning (UAT) is a hybrid machining technique, in which the cutting tool is made to vibrate at high frequencies and low amplitudes. In this study, the machinability and tool wear of machining SiCp/Al metal matrix-composite was compared for dry UAT and conventional turning with the use of a cemented carbide (WC) and a polycrystalline diamond (PCD) tool. With the use of ultrasonic assistance, a significant reduction in cutting forces was achieved with a slight increase in cutting temperature. Continuous and semi-continuous chips were obtained in UAT, with better surface topography. A chip-formation mechanism in UAT show increased ductility of the workpiece material when subjected to a repeated high-frequency microchipping process. Abrasive and adhesive wear occurred on the WC tool in both conventional turning and UAT. However, the machined surface obtained in UAT with a WC tool was comparable and sometimes even better than that achieved with the PCD tool.

Highlights

Metal-matrix composites (MMCs) are increasingly being used in various engineering applications, such as in aerospace, electronics and automotive industries thanks to their high specific strength, high stiffness, low thermal expansion, excellent corrosion and wear resistance. Chawla and Shen (2001) claim that particle-reinforced MMCs are often preferred to continuous-fibre-reinforced MMCs, because of their competitive advantage of low cost, ease of manufacture and nominal isotropic properties
Small reductions of maximum temperature (MT) in conventional turning (CT) (Fig. 5(g)) and Ultrasonically assisted turning (UAT) (Fig. 5(h)) with polycrystalline diamond (PCD) tool and minimum quantity lubrication (MQL) were observed compared to those with the same tool under dry machining conditions (Fig. 5(c, d)). This was due to high tool wear in WC (Section 3.6), the use of MQL had some effect on the chip characteristics but negligible effect on cutting force and temperature
With the MQL use, the surface roughness deteriorates in UAT, showing a 12.2% increase in Ra when compared to surface topography obtained in CT

Summary

Introduction

Metal-matrix composites (MMCs) are increasingly being used in various engineering applications, such as in aerospace, electronics and automotive industries thanks to their high specific strength, high stiffness, low thermal expansion, excellent corrosion and wear resistance. Chawla and Shen (2001) claim that particle-reinforced MMCs are often preferred to continuous-fibre-reinforced MMCs, because of their competitive advantage of low cost, ease of manufacture and nominal isotropic properties. Manna and Bhattacharayya (2003) studied the influence of machining parameters, e.g. cutting speed, feed rate and depth of cut on the cutting force and surface finish criteria They conclude that the use of rhombic tools have advantages in machining when cutting speeds range between 60 m/min to 150 m/ min. Dabade and Joshi (2009) studied the effect of machining parameters and composite composition on chip formation and the effect of chip formation on surface roughness They conclude that in machining of MMCs with coarser reinforcement lead to gross fracture with smaller chip segments and higher shear plane angle. Tool wear was deemed to be the primary drawback in machining MMCs, due to a highly abrasive nature of hard particulate

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