Strain hardening properties and the relationship between strain and hardness of Inconel 718

In micro-milling of Inconel 718, work hardening occurs and the strain hardening properties as well as the relationship between strain and hardness of Inconel 718 remain unclear. The quasi-static tensile tests are conducted in this paper. Through the experiments, the strength coefficient K and the strain-hardening exponent n in Hollomon formula, which describes the relationship between strain and stress of a material, are calculated. After the measurements of the micro-hardness of Inconel 718 under different plastic deformations, the relationship between micro-hardness and strain of Inconel 718 is established. This relationship is valuable in computation of the hardness based on the stress state of Inconel 718 and it also extends the application of the commercial finite element analysis software such as ABAQUS, since it tracks stress state but cannot acquire the hardness of the machined surface. The proposed equation then calculates the hardness value based on the simulation output of stress in the software. [Submitted 18 July 2017; Accepted 28 November 2017]