Recent progress of machinability and surface integrity for mechanical machining Inconel 718: a review

Inconel 718 (IN-718) has excellent mechanical and chemical properties at high temperature, which has been widely applied in aerospace, ocean, and chemical industries. Meanwhile, the super high temperature properties lead to its poor machinability and machined surface integrity. Good machinability and surface integrity of IN-718 have always been challenging topics in the field of mechanical machining. The machinability and surface integrity of IN-718 was reviewed in this paper. The influences of chemical elements, microstructure, cutting parameters, and cutting environments on machinability were discussed. Cutting force, specific energy, and tool wear were analyzed as the main factors of machinability evaluation index. The characteristics of machined surface integrity including surface morphology (such as surface defects and surface roughness), microstructure modifications (such as plastic deformation, grain size, and white layer) and mechanical properties (such as microhardness and residual stress) related to IN-718 were presented. The state-of-the-art of machining IN-718 showed that most current research focused on its poor machinability and surface integrity in the aspect of material characteristics. There is lack of research on machinability from the viewpoint of geometrical structure of the part to be machined. Therefore, it is important to further study the manufacturability (the difficulty of the process from material to part) of IN-718 components with complex geometrical surface and profiles to achieve shape control and precise design.