Experimental study of surface integrity and fatigue life in the face milling of Inconel 718

Abstract

The Inconel 718 alloy is widely used in the aerospace and power industries. The machining-induced surface integrity and fatigue life of this material are important factors for consideration due to high reliability and safety requirements. In this work, the milling of Inconel 718 was conducted at different cutting speeds and feed rates. Surface integrity and fatigue life were measured directly. The effects of cutting speed and feed rate on surface integrity and their further influences on fatigue life were analyzed. Within the chosen parameter range, the cutting speed barely affected the surface roughness, whereas the feed rate increased the surface roughness through the ideal residual height. The surface hardness increased as the cutting speed and feed rate increased. Tensile residual stress was observed on the machined surface, which showed improvement with the increasing feed rate. The cutting speed was not an influencing factor on fatigue life, but the feed rate affected fatigue life through the surface roughness. The high surface roughness resulting from the high feed rate could result in a high stress concentration factor and lead to a low fatigue life.

Key words： roughness; hardness; residual stress; microstructure; fatigue life

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 51675312), a Project of Shandong Province Higher Educational Science and Technology Program (Grant No. J17KZ001), and the Key Laboratory of High-efficiency and Clean Mechanical Manufacture at Shandong University, Ministry of Education.

References

1 Dudzinski D, Devillez A, Moufki A, . A review of developments towards dry and high speed machining of Inconel 718 alloy. International Journal of Machine Tools and Manufacture, 2004, 44(4): 439–456

2 Novovic D, Dewes R C, Aspinwall D K, . The effect of machined topography and integrity on fatigue life. International Journal of Machine Tools and Manufacture, 2004, 44(2‒3): 125–134

3 Reed E C, Viens J A. The influence of surface residual stress on fatigue limit of titanium. Journal of Engineering for Industry, 1960, 82(1): 76–78

4 Darwish S M. The impact of the tool material and the cutting parameters on surface roughness of supermet 718 nickel superalloy. Journal of Materials Processing Technology, 2000, 97(1-3): 10–18

5 Sharman A R C, Hughes J I, Ridgway K. An analysis of the residual stresses generated in Inconel 718^TM when turning. Journal of Materials Processing Technology, 2006, 173(3): 359–367

6 Devillez A, Le Coz G, Dominiak S, . Dry machining of Inconel 718, workpiece surface integrity. Journal of Materials Processing Technology, 2011, 211(10): 1590–1598

7 Pusavec F, Hamdi H, Kopac J, . Surface integrity in cryogenic machining of nickel based alloy—Inconel 718. Journal of Materials Processing Technology, 2011, 211(4): 773–783

8 Guo Y B, Li W, Jawahir I S. Surface integrity characterization and prediction in machining of hardened and difficult-to-machine alloys: A state-of-art research review and analysis. Machining Science and Technology, 2009, 13(4): 437–470

9 Ulutan D, Ozel T. Machining induced surface integrity in titanium and nickel alloys: A review. International Journal of Machine Tools and Manufacture, 2011, 51(3): 250–280

10 Hashimoto F, Guo Y B, Warren A W. Surface integrity difference between hard turned and ground surfaces and its impact on fatigue life. CIRP Annals-Manufacturing Technology, 2006, 55(1): 81–84

11 Warren A W, Guo Y B. The impact of surface integrity by hard turning vs. grinding on rolling contact fatigue. In: Proceedings of ASME 2007 International Manufacturing Science and Engineering Conference. Atlanta: ASME, 2007, 473–481

12 Guo Y B, Warren A W. The impact of surface integrity by hard turning vs. grinding on fatigue damage mechanisms in rolling contact. Surface and Coatings Technology, 2008, 203(3‒4): 291–299

13 Smith S, Melkote S N, Lara-Curzio E, . Effect of surface integrity of hard turned AISI 52100 steel on fatigue performance. Materials Science and Engineering A, 2007, 459(1‒2): 337–346

14 Matsumoto Y, Magda D, Hoeppner D W, . Effect of machining processes on the fatigue strength of hardened AISI 4340 Steel. Journal of Manufacturing Science and Engineering, 1991, 113: 154–159

15 Jeelani S, Musial M. Effect of cutting speed and tool rake angle on the fatigue life of 2024-T351 aluminium alloy. International Journal of Fatigue, 1984, 6(3): 169–172

16 Javidi A, Rieger U, Eichlseder W. The effect of machining on the surface integrity and fatigue life. International Journal of Fatigue, 2008, 30(10‒11): 2050–2055

17 Sasahara H. The effect on fatigue life of residual stress and surface hardness resulting from different cutting conditions of 0.45%C steel. International Journal of Machine Tools and Manufacture, 2005, 45(2): 131–136

18 Wang X, Huang C, Zou B, . Tool life of coated tools in face milling of GH4169 at various cutting speeds. Materials Science Forum, 2013, 770: 126–129

19 Wang X, Huang C, Zou B, . A new method to evaluate the machinability of difficult-to-cut materials. International Journal of Advanced Manufacturing Technology, 2014, 75(1‒4): 91–96 doi:10.1007/s00170-014-6126-7

20 Zheng X. A further study on fatigue crack initiation life—Mechanical model for fatigue crack initiation. International Journal of Fatigue, 1986, 8(1): 17–21