Tool wear acceleration in relation to workpiece reinforcement percentage in cutting of metal matrix composites

A comprehensive study of the tool wear mechanism in cutting of metal matrix composites (MMCs) and its dependence on the percentage of reinforcement in the MMCs is presented. The results from machining of aluminium alloy-silicon carbide metal matrix composite (Al-SiC MMC) with tungsten carbide tools show that the main mechanism of tool wear in cutting of Al-SiC MMC includes two-body abrasion and three-body abrasion. The abrasive wear of the tool is accelerated when the percentage of the reinforcement in the MMC exceeds a critical value. The wear acceleration is caused by the interference between the reinforcement particles. The interference is associated with a critical weight percentage of the reinforcement in the MMC. The critical weight percentage of reinforcement is a function of the densities of the reinforcement and the matrix as well as the size of the reinforcement particles and the radius of the tool cuffing edge. It does not vary with cutting conditions. An analytical model for the critical reinforcement percentage of MMCs is developed and verified with experimental results. The model is used to develop a map showing the critical reinforcement percentages of MMCs varying with the size of the reinforcement particles and the radius of the tool cutting edge. (C) 2001 Elsevier Science B.V. All rights reserved.