Wettability and machinability study of pure aluminium towards uncoated and coated carbide cutting tool inserts

An investigation has been conducted to study wetting characteristics of aluminium towards different cutting tool materials for assessing the compatibility for dry machining of aluminum. For this purpose uncoated carbide (94%WC + 6%Co) and mono or multi-layer coated carbide tools with top coating of TiC, TiN, Al2O3 and diamond have been used. It was observed that aluminium had a tendency to wet uncoated carbide (94%WC + 6%Co) inserts. However, wetting was more pronounced when surface was enriched with cobalt. In contrast, wetting of aluminium was less when the WC content of the carbide tool surface increased. Coatings like TiC, TiN or Al2O3 could not show pure non-wetting characteristics for aluminium. The aluminium appeared to dissolve the coatings in different degrees. On the other hand, coating of diamond exhibited inertness towards aluminum leading to non-wetting behaviour. Turning test with aluminium indicated heavy material built up on uncoated (94%WC + 6%Co) tool. Built up edge formation could not be avoided when carbide inserts with a top coating of TiC, TiN, Al2O3 were engaged in machining of aluminium. However, the non-wetting characteristic of diamond coating was reflected during machining of aluminium. The chips slided smoothly over the rake face leaving no trace of edge built up.