Tool Engage Investigation in Nickel Superalloy Turning Operations

Turning operations on complex components such as aircraft engines casings require the insert replacement at the end of each geometric feature manufacturing, independently from the actual tool wear level. For this reason, it is important to generally preserve tool integrity during the machining operation especially when the tool engages the workpiece (i.e., the most critical phase of operation). In fact, if the tool is damaged in this stage the quality of the whole operation is compromised. The attention has been focused on engage cutting conditions since the phenomenon that appears in this critical step plays a large influence on tool integrity and, consequently, on the quality of the operation. For this purpose a ring-workpiece of nickel-based super alloy (Inconel 718) has been machined in lubricated cutting conditions by using a CNC lathe with carbide coated tools. Two variables have been investigated in this study: the Depth Of Cut (DOC) and the approaching Engage angle (En), while the Cutting Speed (S), Feed-rate (F) and removed volume (Vrim) were kept constant. Both tool wear and cutting forces evolution during cutting have been analyzed.