Aspects on superalloy machining

Abstract

Superalloys have a chemical composition with high content of alloying elements, which are responsible for their mechanical and thermal properties; however, these features difficult the machining, leading to occurrence of some troubles during the process. Because of its high mechanical strength and low thermal conductivity, there is a concentration of heat at high temperatures, mainly on the chip-tool interface that complicates its machinability. The objective of this work is the presentation of results obtained during machining study for turning with finishing parameters of the two alloys: Nimonic 80A and Pyromet 31V. In these works were tested alloys both as hot rolled as solubilized and aged, using coated and uncoated cemented carbide tools, with flood fluid applictaion and minimal quantity lubrication (MQL). The wear mechanisms acting for both alloys, using coated tools, the most common were abrasion, attrition, chipping and hammering. While to machining with uncoated tools, the main wear mechanisms were cratering by diffusion, abrasion and oxidation action (notches). The chips shape generated during tests with Pyromet was diverse but predominantly long and it is also highlighted the presence of double chip. Only minor chips was observed with MQL technique. In tests with Nimonic, for some parameters settings it was possible to obtain short chips, but the occurrence of long chips was more frequent for tested conditions.