MACHINING OF AL SIC PARTICULATE METAL-MATRIX COMPOSITES - PART I - TOOL PERFORMANCE/

Despite the superior mechanical and thermal properties of particulate metal-matrix composites, their poor machinability has been the main de terrent to their substitution for metal parts. The hard abrasive reinf orcement phase causes rapid tool wear during machining and, consequent ly, high machining costs. A series of dry high-speed turning tests wer e performed to select the optimum tool material, tool geometry and cut ting parameters for the turning of 20%SiC/Al metal-matrix composites. The results indicate that polycrystalline diamond tools (PCD) provide satisfactory tool life compared to alumina and coated-carbide tools, w here the latter tools suffered from excessive edge chipping and crater wear during the machining of the metal-matrix composite under study. Furthermore, the cost of PCD tools could be justified by using dry cut ting at feed rates as high as 0.45 mm rev(-1), cutting speeds of 894 m min(-1) and a depth of cut of 1.5 mm. With these cutting parameters, the relatively small built-up edge formed on the tool protects it from further wear by abrasion and micro-cutting. Polycrystalline tools wit h zero rake angle and large tool nose radii are recommended for the ro ughing operations. (C) 1998 Elsevier Science S.A. All rights reserved.