High-speed turning of Inconel 718 by using TiAlN- and (Al, Ti) N-coated carbide tools

High-speed turning of Inconel 718 was challenged by using TiAlN-coated tungsten carbide tools of positive and negative types, and aluminum-rich (Al, Ti) N-coated ones of negative type. It is found that the (Al, Ti) N negative inserts have much longer tool life than the TiAlN inserts of both the positive and negative types at all the cutting speeds tested. The skirt flank wear was almost the same in mechanism, which was dominated by adhesive wear and abrasive wear for the three types of inserts at the all cutting speeds tested. The cutting edge flank wear changed greatly both in magnitude and in mechanism depending on the type of the insert and the cutting speed. The rake wear was almost limited within the cutting area and at tool life the coatings in the cutting area were all worn off except of the (Al, Ti) N negative inserts tested at the cutting speed of 200 m/min. The hardness of the turned surfaces was always higher than that as received, and the increase in the hardness was greatest for the (Al, Ti) N negative inserts among the three types of the inserts.