Tool wear and machinability of X5 CrMnN 18 18 stainless steels

In this study, active wear and failure mechanisms of TiN-coated cemented carbide tools when machining X5 CrMnN 18 18 austenitic stainless steel have been investigated. By nitrogen alloying austenite is stabilised and the strength of austenitic stainless steel is increased and work hardening is promoted. Stainless steels are often considered as poorly machinable materials. High strength and work hardening rate cause difficulties from the machining point of view. In this study turning tests carried out by using a test lathe and a cutting force measuring device are presented. Chips were analysed by scanning electron microscopy. The machinability of X5 CrMnN 18 18 austenitic stainless steels is examined based on tool life and cutting speed presented by vT-diagrams. The effect of cutting speed and nitrogen content is also analysed by cutting force measurements. Based on the cutting tests, cutting speeds of 40–200 m/min, feed rate of 0.15–0.25 mm and depth of cut of 1.6 mm for X5 CrMnN 18 18 stainless steels can be applied from machinability point of view. Higher nitrogen content decreases cutting force and decreases machinability. Tool wear criterion, VB-value of 0.3 mm, is reached after turning time of 10 min, when 60, 65 and 70 m/min and 0.24 mm/r feed rates are utilised.