Machinability study of pure aluminium and Al-12% Si alloys against uncoated and coated carbide inserts

An investigation has been undertaken to study the compatibility of cutting materials in dry machining of aluminium and Al-Si alloys. Mono or multilayer coated carbide tools with a top coating of TiC, TiN, TiAlN, Al2O3, TiB2, MoS2 etc. on WC-Co inserts already made a major breakthrough in dry machining of ferrous materials. But in contrast dry machining of aluminium and Al-alloys is a great challenge. But wide application of aluminium different parts has increased the need to find out the correct cutting tool. Experimental results of turning test, SEM pictures and chip morphology investigation of the cutting tool after machining clearly reveals the inefficiency of TiC, TiN, TiB2, Al2O3, and AlON in dry machining of aluminium. This is because of the formation of very large amount of metal built-up in both rake and flank surface leading to high magnitude of cutting forces and high roughness of the work-piece during machining. The natural diamond and polycrystalline diamond (PCD) can be used as a cutting tool, when the required shape is attached on the edge/tip for machining non-ferrous materials. But both of them are limited for finishing cut because of high cost. So CVD diamond coated tool is a better option to machine these materials. CVD diamond coated tool was free from built-up edge formation leading to clean cut, low magnitude of cutting forces and improved surface finish of the work-piece. However, performances of the diamond tool depend mainly on adhesion of the diamond coating with the carbide substrate. (C) 2008 Published by Elsevier Ltd.