THE TURNING OF AN AL/SIC METAL-MATRIX COMPOSITE

Metal-matrix composites are a relatively new range of materials possessing several characteristics that make them useful in situations where low weight, high strength, high stiffness, and an ability to operate at elevated temperatures are required. These materials are difficult to machine, however, consisting of a hard abrasive ceramic reinforcing medium set within a more ductile matrix material. This paper presents results from a series of turning tests in which a number of different cutting-tool materials were used to machine an Al/25 vol% SiC metal-matrix composite. The influence of the cutting speed on the tool wear, the surface finish, and the cutting forces was established for each tool material. It was found that carbide tools, both coated and uncoated, sustained significant levels of tool wear after a very short period of machining. The best overall performance was achieved using a solid cubic boron nitride, CBN, insert whilst the worst was encountered using a solid silicon nitride, Sylon, tool.