Improved metal cutting performance with biasmodulated textured Ti0.50Al0.50N multilayers

In this work we present the cutting performance of Ti0.50Al0.50N coatings which have been deposited with both a fixed and an alternating bias of -35 V and -70 V together with a Ti0.33Al0.67N reference coating grown at -35 V. During deposition of the bias-layered coatings, the bias was instantaneously changed with four different bias-layer periods ranging from approximately 250 to 1500 nm. For the layers deposited with a fixed bias, a transition from a (100) to a (111) preferred orientation was observed with the change in bias from -35 V to -70 V. The coatings grown with an alternating bias, however, show a (111) preferred orientation with an intensity that slightly depends on bias-layer period. Metal cutting tests were performed in 100Cr6 steel with a cutting speed of 200 m/min, feed of 0.2 mm/rev and a depth of cut of 2 mm. The wear resistance was quantified in terms of crater and flank wear resistance showing an improvement for all bias-layered coatings. This is attributed to a (111) oriented refined grain structure in combination with low residual stresses in the coating.