THE DRILLING OF AN AL/SIC METAL-MATRIX COMPOSITE

Because of the hard ceramic reinforcing component in a metal-matrix composite, these materials are difficult to machine and attempts to do so result frequently in accelerated tool wear and premature failure. This paper reports on the results from a series of drilling tests undertaken on a 25% volume fraction Al/SiC metal-matrix composite. A range of tool materials was tested, these including: coated and uncoated high-speed steel, carbide and PCD-tipped drills and solid-carbide drills. The results indicate that the hardness of the tool material has a significant influence on cutting-edge wear and on the drilling-torque and thrust-forces experienced. It was found also that the presence of a ceramic coating on a high-speed steel drill does not improve its performance appreciably, compared to standard un-coated tools.