Study on the Formation Mechanism of Serrated Chips in the Cutting Process of Powder Metallurgy Superalloys Based on a Modified J–C Constitutive Relation Simulation Model

Abstract

Powder metallurgy superalloys are attracting great attention due to their unique performance advantages, such as good oxidation resistance, corrosion resistance, excellent tensile behavior, durability, fatigue properties, and long-term tissue stability. Therefore, powder superalloys show strong vitality in the field of advanced aerospace engines. However, the cutting force is large, and the serrated chips lead to poor machinability in the cutting process. The influence of dynamic recrystallization softening on serrated chips in the cutting process cannot be ignored. In this paper, the formation mechanism of serrated chips in the FGH96 cutting process is studied considering the influence of dynamic recrystallization softening. Firstly, based on the J–C constitutive relation modified by the recrystallization stress softening established previously, a finite element simulation model of the right-angle cutting of FGH96 is established. According to the results of the simulation model, the variation law of the thermal mechanical loading field in the formation process of serrated chips is quantitatively characterized. The validity of the simulation model is verified by comparison with the cutting force, chip morphology, and strain rate obtained from the experiment. Simulation results show that, in the formation process of serrated chips, the temperature field, strain field, and strain rate field in the first deformation zone show similar distribution characteristics to the shear band distribution, and with the formation of serrated chips, their values gradually increase. On this basis, the formation mechanism of serrated chips is revealed, which is the stage of serrated chip initiation, the stage of generating 50% serrated chips, the stage of generating 75% serrated chips, and the stage of serrated chip formation.