Investigation on the machining characteristics of AZ91 magnesium alloy using uncoated and CVD-diamond coated WC-Co inserts

An investigation has been performed to study the compatibility of machining AZ91 magnesium alloy in dry conditions using uncoated and CVD diamond-coated WC-Co inserts. The machining characteristics such as built-up edge (BUE) formation, surface roughness, cutting forces and chip morphology were studied at the cutting speeds, 350, 650 and 950 m/min. The results revealed severe adhesion of the AZ91 Mg alloy on the uncoated WC-Co inserts with increasing cutting speed and contributed to an increase in surface roughness and cutting forces. The CVD diamond-coated inserts have shown negligible built-up edges at various cutting speeds due to their unique properties like low coefficient of friction, low chemical affinity and high thermal conductivity. Snarled types of long continuous chips were observed while machining with CVD diamond-coated WC-Co inserts, whereas short continuous chips were observed with uncoated WC-Co inserts.