ALUMINUM-BASED MMC MACHINING WITH DIAMOND-COATED CUTTING TOOLS

Automotive, aerospace and train companies need to replace steel and ca st iron in mechanical components with lighter high-strength alloys lik e Al metal matrix composites (MMC). The weight savings will lead to a reduction in the fuel consumption and environment impact. Automotive p roducers are testing prototypes in Al-MMCs such as brake disk and drum , callipers, piston and cylinder liners. The main limit in the MMC app lications at high production volumes is the difficulty and the high co st of the machining operations (turning, milling, drilling, threading) due to the extreme abrasive properties of these materials. In fact, t he MMCs reinforcement particles are very hard and produce a quid; incr ease in the tool wear rate due to the abrasion of the cutting edge. Ti ll now the use of MMC and Al hypereutectic alloys in the automotive, r ailway and aerospace industries has been limited by the following aspe cts: the high machining costs due to the short standard tool life; the PCD toolings an not available for complex-shape cutting tools (e.g. t aps, or very small diameter drills and reamers); during the MMC parts machining a SiC powder formation occurs with the coolant pollution and , moreover, with a degradation of machine tool components (hard partic les), and with a drastic decrease of PCD tool cutting life (built-up e dge formation). In this paper we present the results of experimental m achining tests in different cutting operations with a comparison betwe en standard tungsten carbide tools, PCD and CVD diamond-coated cutting tools with the relative problems in the high production machining of MMC and Al hypereutectic components; conclusions drawn and the possibl e future developments are presented. (C) 1997 Elsevier Science S.A.