**5. Conclusions**

Despite significant progress in the traditional cutting tool technologies, the machining of INCONEL® 718 and 625 is still considered a great challenge because of the intrinsic characteristics of those Ni-superalloys. It is notable, nevertheless, that there has been a pursuit to bring ease to conventional processes, resulting from the evolution of techniques and tool materials, to get better machinability with the Ni-based superalloys. From another point of view, by introducing non-conventional processes and assists like EDM, and hybrid techniques such as LAM and UAT, the evolution differential has a great potential to bring down manufacturing costs. Likewise, the conventional processes have had several improvements in the last five years, as reviewed along all states of the art, calling upon Taguchi DOE methods for improving tool-wear and for improving *R*a, either with a lubrication environment or not. This is important for the own component's wear resistance. A constructive criticism is made of the usage of TGRA and DOE methods, which were several times noticed to be used by different research in the states of the art of this paper. It is efficient to take advantage of such powerful methods to evaluate a series of parameters in an Lx array, and through the combination between them, to achieve the best result of *R*a. Nonetheless, it is known that one of the main challenges in tackling INCONEL® machining is the high costs of the manufacturing processes, due to the elapsed time milling, and turning, and this key factor has been neglected. With this review paper, it is suggested to the forthcoming authors to take advantage of TGRA and ANOVA analyses, concerning the achievement of low-cost solutions when machining INCONEL®, at the same time quality is preserved by taking *R*a parameter into account as it has been done so far. The present work highlighted a large amount of information regarding INCONEL® 718 traditional machining and applications, within the academic and scientific community, compared to its counterpart INCONEL® 625. On the other hand, the INCONEL® 625 showed advancements in non-conventional processes due to difficulties at the onset of chip cutting. Henceforward, research work is planned with the prospect of delivering a review paper regarding the evolution of lubrication environments, allied to the traditional machining of INCONEL®.

**Author Contributions:** Conceptualization: A.F.V.P., F.J.G.S. and R.D.S.G.C.; methodology: A.F.V.P., F.J.G.S. and R.D.S.G.C.; validation: V.F.C.S., N.P.V.S. and A.M.P.J.; formal analysis: F.J.G.S., V.F.C.S. and R.C.M.S.-C.; investigation: A.F.V.P.; data curation: F.J.G.S., R.C.M.S.-C. and A.M.P.J.; writing—original draft preparation: A.F.V.P.; writing—review and editing: V.F.C.S., F.J.G.S., R.D.S.G.C. and R.C.M.S.-C.; visualization: R.C.M.S.-C. and A.M.P.J.; supervision: F.J.G.S. and R.D.S.G.C.; project administration: F.J.G.S.; funding acquisition: F.J.G.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The work is developed under the "DRIVOLUTION—Transition to the factory of the future", with the reference DRIVOLUTION/BL/01/2023 research project, supported by European Structural and Investments Funds with the "Portugal2020" program scope.

**Data Availability Statement:** No new data was created.

**Acknowledgments:** The authors thank ISEP and INEGI for their support.

**Conflicts of Interest:** The authors declare no conflict of interest.
