1. LIFE 40 App. B High temperature fatigue crack propagation in nickel-based superalloys Erik Lundström & Jonas Saarimäki Linköping University

2. Outline Background Motivation Hold times Behaviour Industry practice Modelling approach Lic. Thesis E. Lundström Ongoing testing New test geometry Test rigs Future work 2

3. Background Deformation and damage mechanisms at high temperature and loads The knowledge will help us to develop material models that can be used for FEM simulations More efficient power generation by gas turbines 3

4. Background; cont. 4 Area of interest = HPT discs F110-GE-100

5. Background; cont. 5 Wanhill, R. Significance of dwell cracking for IN718 turbine discs International Journal of Fatigue, 2002, 24, 545 - 555

6. Motivation Inconel 718 is the most common superalloy in the gas turbine industry The alloy is (among others) sensitive to embrittling elements Sustained load – cruise or constant power output Slow ramp-up of engine thrust Slow shut-downs Life prediction with time dependent loading A lack of robust models Increase in TRL Incorporation into the gas turbine industry life prediction programs 6

7. Hold times 7

8. Transgranular and intergranular fracture 8 Fracture modes

9. Modelling – industry standard Current industry standard 9

10. Modelling – industry standard; cont. 10

11. Modelling – industry standard; cont. 11

12. Damaged zone Differences from PD prediction and final fracture surface – ligaments in the crack wake which are electrically conductive This is henceforth referred to as the damaged zone D 12 Crack length by PD Microstructural crack length = a+D

13. Modelling Should be able to handle a wide spectrum of hold times Should require few input parameters Should be able to be modified to function over a wide range of conditions Non-isothermal Varying load ratios – presented at FATIGUE2014 Overloads / underloads – published in Phase 2 Should be easy to use on a daily basis as an engineering tool for practical use 13

14. Modelling; cont. 14

15. Modelling; cont. Calibration test for cheap and easy parameter determination 1 test type for 8 model parameters Time dep. parameters C 0t, n t and B t Cyclic parameters C c, n c, A c and B c Maximum damaged zone length D max Additional tests if scatter is to be handled 15

16. Modelling; cont. 16 BtBt A c B c C 0t n t C c n c D max da/dt da/dN K max ΔKΔKΔKΔK Load Time

17. Modelling; cont. 17

18. Statistics 18

19. Statistics - comparison 19 Developed modelling approachIndustry standard

20. Lic. Presentation E. Lundström 20

21. Paper 1 – Overload behaviour 21

22. Paper 2 – Initial modelling 22

23. Paper 3 – Modelling and evaluation 23 Paper 2

24. Paper 4 – Application to a flight spectrum 24 Paper 3

25. A deeper insight in paper 4 - Application Application to a flight spectrum TRL increase 25

26. Application; cont. 26

27. Application; cont. 27 566 sequences (1468s each) in total for the test Test to model error of ~13%

28. Application; cont. 28

29. Paper 5 – Fracture surface investigation 29 Paper 3

30. Modelling work - summary A history dependent model based on LEFM Cheap and easy calibration – 1 test needed (8 parameters) Only need to keep track of 1 additional parameter (D) for handling history dependence Easy to incorporate into existing life prediction codes Validated through a wide range of load sequences and temperatures 30

31. Ongoing testing Kb specimens Wrought IN718 Cast IN718 Wrought EBW IN718 CT specimens (side-groove) Wrought IN718 Wrought Haynes 282 31

32. Ongoing testing; cont. Test procedure CT specimens Inconel 718 Haynes 282 32

33. Ongoing testing; cont. Test rig Zwick 33

34. Ongoing testing; cont. PD-modeling Validation and estimation of a+D 34 Electrical potential V Crack length a Electrical potential V Crack length a

35. Component and/or breadboard validation in laboratory environment Future work 35 TRL ABAQUS TRL 6 System/subsystem model or prototype demonstration in a relevant environment TRL 4

36. Deliverables – phase 2 3 papers in international journals D. Gustafsson, E. Lundström (2013). High temperature fatigue crack growth behaviour of Inconel 718 under hold time and overload conditions, International Journal of Fatigue, Volume 48, pp. 178-186. D. Gustafsson, E. Lundström, K. Simonsson (2013). Modelling of high temperature fatigue crack growth in Inconel 718 under hold time conditions, International Journal of Fatigue, Volume 52, pp. 124-130. E. Lundström, K. Simonsson, D. Gustafsson, T. Månsson (2014). A load history dependent model for fatigue crack propagation in Inconel 718 under hold time conditions, Engineering Fracture Mechanics, Vol. 118, pp. 17- 30. 36

37. Deliverables – phase 2; cont. 2 paper submitted for publication in an international journal E. Lundström, K. Simonsson (2014). Evaluation and prediction of crack length in a Ni-based superalloy for sustained loading, submitted. J. Saarimäki, J. Moverare, R. Eriksson, S. Johansson (2014). Influence of overloads on dwell time fatigue crack growth in Inconel 718, submitted. 37

38. Deliverables – phase 2; cont. 4 presentations at an international conference D. Gustafsson (2012). Overload considerations for holdtime fatigue crack growth in Inconel 718, International Conference on Fatigue Damage of Structural Materials IX. E. Lundström and J. Saarimäki et al. (2013). High temperature hold time fatigue crack growth behaviour of Inconel 718, CEAS2013. H. Brodin, J. Saarimäki (2013). Mechanical properties of lattice truss structures made of a selective laser melted superalloy, ICF13. E. Lundström, K. Simonsson, T. Månsson, D. Gustafsson (2014). Modelling of fatigue crack growth in Inconel 718 under hold time conditions - application to a flight spectrum, Advanced Materials Research, Volumes. 891-892, pp. 759-764. FATIGUE 2014 38

39. Deliverables – phase 2; cont. 1 Dissertation D. Gustafsson (2013). High temperature fatigue crack propagation behaviour of Inconel 718 – Dissertation. 1 Lic. Thesis. E. Lundström (2014). Modelling of fatigue crack propagation in Inconel 718 under hold time conditions – Lic. Thesis. 4 master thesis 39

40. Thank you for your attention! 40